Reader TTS

ABSTRACT Natural and anthropogenic gas radionuclides such as radon, xenon, hydrogen and krypton isotopes must be monitored to be managed as pathogenic agents, radioactive diagnostic agents

or nuclear activity indicators. State-of-the-art detectors based on liquid scintillators suffer from laborious preparation and limited solubility for gases, which affect the accuracy of the

measurements. The actual challenge is to find solid scintillating materials simultaneously capable of concentrating radioactive gases and efficiently producing visible light revealed with

high sensitivity. The high porosity, combined with the use of scintillating building blocks in metal–organic frameworks (MOFs), offers the possibility to satisfy these requisites. We

demonstrate the capability of a hafnium-based MOF incorporating dicarboxy-9,10-diphenylanthracene as a scintillating conjugated ligand to detect gas radionuclides. Metal–organic frameworks

show fast scintillation, a fluorescence yield of ∼40%, and accessible porosity suitable for hosting noble gas atoms and ions. Adsorption and detection of 85Kr, 222Rn and 3H radionuclides are

explored through a newly developed device that is based on a time coincidence technique. Metal–organic framework crystalline powder demonstrated an improved sensitivity, showing a linear

response down to a radioactivity value below 1 kBq m−3 for 85Kr, which outperforms commercial devices. These results support the possible use of scintillating porous MOFs to fabricate

sensitive detectors of natural and anthropogenic radionuclides. SIMILAR CONTENT BEING VIEWED BY OTHERS REAL-TIME DETECTION AND DISCRIMINATION OF RADIOACTIVE GAS MIXTURES USING NANOPOROUS

INORGANIC SCINTILLATORS Article Open access 02 September 2024 DEVELOPMENT AND CHALLENGES IN PEROVSKITE SCINTILLATORS FOR HIGH-RESOLUTION IMAGING AND TIMING APPLICATIONS Article Open access

13 March 2023 HYBRIDISATION OF PEROVSKITE NANOCRYSTALS WITH ORGANIC MOLECULES FOR HIGHLY EFFICIENT LIQUID SCINTILLATORS Article Open access 07 September 2020 MAIN Natural radioactive gases

such as the isotopes of radon (222Rn and 220Rn), and the anthropogenic radionuclides coming from fission (133Xe and 85Kr) and activation (3H and 37Ar) products, need to be carefully

monitored. Isotopes such as 85Kr and 3H, which originate from nuclear power plants, reprocessing plants and nuclear waste treatments1,2,3,4,5, are critical to detect for monitoring nuclear

activity and uncovering illegal reprocessing to produce plutonium for weapons6. 133Xe and 37Ar are of key interest, as they can be used to detect covert activities to verify compliance with

the Comprehensive Nuclear-Test-Ban Treaty7. On the other hand, gases from granite-rich areas (222Rn and 220Rn)8,9,10 are pathogenic agents that must be quantified to mitigate the exposure

risk, whereas xenon isotopes are useful as radioactive diagnostic contrast agents to evaluate pulmonary function, lung imaging and cerebral blood flow by inhalation11,12,13. The detection

and radioactivity metrology of gases is thus a crucial aspect in a modern, technologically advanced and sustainable society, as demonstrated by the recurrent updates of regulations that ask

for increasingly more sensitive and accurate detectors14,15. All of the listed radionuclides decay by emitting β-particles (α- and β-particles the case of radon); that is, electrons that are

difficult to detect due to their short-range path in matter, especially for 3H (ref. 16). In this case, the liquid scintillation counting technique is the gold standard to measure

radioactivity, but it requires a long and complex procedure to mix 3H-labelled water with the scintillator17. This hinders in situ online measurements and produces liquid radioactive waste

that must be carefully managed. Moreover, it cannot be applied to other gas radionuclides, which are highly insoluble. In this case the only option is to use gas meters that require large

volumes and counting gases to increase the detection efficiency, resulting in very impractical instrumentation (see Supplementary Section 11). A key solution to bypass these issues is to use

solid porous scintillators: the adsorption and accumulation in the pores would concentrate the radionuclide, while simultaneously enhancing the probability of the scintillators interacting

with the generated ionizing radiation, thus increasing the device sensitivity. Porous scintillators would allow the use of low detection volumes, thus enabling the realization of practical

small instruments for in situ operation. Importantly, the porous systems can also be cleaned from radioactive species and reused, thus enabling a sustainable technology that reduces risks

and costs. Porous scintillators are therefore proposed as a new class of scintillating materials for the development of highly responsive and universal radioactive gas detectors based on

time-coincidence techniques (Fig. 1a)18. Scintillating metal–organic frameworks (MOFs) endowed with high porosity are excellent candidates. The controlled self-assembly of inorganic nodes

and organic ligands produces tailored architectures with well-defined porosity for gas capture, separation and storage19,20,21,22. Metal–organic frameworks have also been used as sorbents

for the sequestration of noble gases23 and, in some cases, ion radionuclides24. Luminescent chromophores, included as ligands or guests, can be integrated to build emissive materials with

unique photophysical25,26,27,28 and scintillating properties26,27,28. However, despite recent MOF developments as colorimetric- and fluorescence-sensing platforms29 and scintillators, their

potential application for the detection of gas radioactivity has not yet been reported. Indeed, luminescent MOFs have been used to detect the presence of a few radioactive analytes in

solution, but without any correlation to their radioactive properties30. Here we demonstrate the capability of porous hafnium-based MOFs containing the dicarboxy-9,10-diphenylanthracene

(DPA) as a scintillating ligand for gas-radioactivity detection (Fig. 1). The crystalline MOF shows a highly accessible porosity suitable for hosting radioactive gases, which transfer their

ionizing radiation to the framework, producing fast scintillation appropriate for time coincidence detection techniques and a good fluorescence quantum yield of ∼40%. The heavy hafnium

improves the interaction with ionizing radiation and enables a good light intensity output, that is, one order of magnitude larger than a commercial scintillator. These excellent properties

prompt us to test the sorption and detection of 85Kr, 222Rn and 3H radionuclides in a newly developed device that exploits the scintillating MOF powder as a gas harvester and concentrator

(Fig. 1a). Metal–organic frameworks show an improved sensitivity with respect to the reference powders currently tested for gas detection, as well as an excellent linear response down to an

activity value of below 1 kBq m−3 for 85Kr, thus outperforming commercial detectors in a compact, cost effective and easy-to-handle architecture. The combination of porosity, good quantum

yield and fast scintillation strongly support the possible use of scintillating porous MOFs as active components to fabricate technologically superior sensors for detecting natural and

anthropogenic radioactive gases at ultralow concentrations. RESULTS GAS ADSORPTION AND PHOTOLUMINESCENCE PROPERTIES OF HF-BASED MOFS Hafnium-based MOFs comprising luminescent DPA ligands

(Hf-DPA) were obtained through solvothermal synthesis (see Methods and Supplementary Figs. 1–7)27,28, which has been optimized to produce octahedral crystals with a cubic crystal structure

385 nm in diameter (Fig. 2a,b)—at which size the emission properties are best—in highly reproducible batches from few tens of milligrams up to ~200 mg (Supplementary Table 1 and

Supplementary Figs. 8–20). Low-temperature gas adsorption isotherms demonstrate the microporous nature of Hf-DPA, and the adsorption of noble gases such as argon and krypton (Fig. 2c and

Supplementary Fig. 30). The argon and krypton adsorption isotherms were also measured at room temperature, demonstrating the gas diffusion inside the cavities under pressure and temperature

conditions comparable with the operational scenario of radioactive gas detection (Supplementary Fig. 31). In this regard we provide direct detection of noble gas diffusion into the pores of

the Hf-DPA by hyperpolarized 129Xe NMR experiments, even in competition with other gaseous species and under flow conditions (Fig. 2d, Methods, Supplementary Table 5 and Supplementary Fig.

28)28,31,32,33,34,35. The detection of the signal at _δ_ = 97.7 ppm within 200 ms demonstrates the fast diffusion in the restricted pores. Figure 2e shows the steady-state photoluminescence

and excitation photoluminescence (PLE) spectra of Hf-DPA dispersed in tetrahydrofuran (see Methods). Under ultraviolet excitation, the dispersion exhibits a blue fluorescence peak at 450 nm,

with a characteristic average decay time of 2.8 ns and a photoluminescence quantum yield of 0.41 ± 0.06 (Supplementary Section 7). The broad spectrum mirrors the presence of a distribution

of local environments and quenching pathways for the emitting ligands25,26,35. The excitation photoluminescence profile recorded at 450 nm matches the vibronic structure of DPA molecules35.

Low-temperature measurements show a blue shift of the photoluminescence maximum to 440 nm, ascribed to the band narrowing at cryogenic temperatures that reduces self-absorption, and an

increased decay time of 3.3 ns, which indicates an emission yield increment to \(0.41\times \tfrac{3.3\,{\mathrm{ns}}}{2.8\,{\mathrm{ns}}}=0.48\) (+18%). This confirms the absence of

substantial thermal quenching in Hf-DPA by intramolecular vibrational mechanisms25,26,35. Figure 2f reports the photoluminescence properties of the Hf-DPA powder that will be used to detect

the gas radionuclides. The emission at room temperature is red shifted to 490 nm due to the larger inner filter effect of self-absorption in the powder, whereas the PLE profile matches that

of MOF in THF. The emission lifetime of 2.4 ns is basically unchanged. At 77 K, the emission maximum is again slightly blue shifted to 480 nm with a lifetime increment to 3.5 ns, confirming

that the excited state electronic properties of the MOF powder are consistent with those of single crystals in diluted dispersion. SCINTILLATION PROPERTIES OF HF-DPA Figure 3a shows the

steady-state scintillation (radioluminescence) spectrum of Hf-DPA powder compared with the commercial plastic scintillator EJ-276 (Methods) under soft X-rays. The MOF powder

radioluminescence matches the photoluminescence profile (Fig. 2f). Notably, despite the Hf-DPA density of 0.6–0.7 g cm−3 being lower than the 1.1 g cm−3 of EJ-276, the scintillation

generated by MOFs is more than one order of magnitude intense (Fig. 3a). This is ascribed to the presence of heavy hafnium ions (_Z_ = 72) enhancing the interaction with ionizing radiation,

which allows the scintillation efficiency of the Hf-DPA to double with respect to the parent zirconium-based MOF (Supplementary Fig. 32)25. Hf-DPA produces a fast scintillation light pulse

(Fig. 3a, inset) with a subnanosecond rise time and average decay time of 3 ns, which matches the photoluminescence decay dynamics. This confirms that the MOF emission properties are

preserved under X-ray excitation. The photoluminescence and radioluminescence of Hf-DPA have been monitored against temperature. Figure 3b shows the MOF powder normalized photoluminescence

spectra recorded cooling from 300 K to 10 K. At low temperature, the emission maximum wavelength shifts to 480 nm due to the mitigation of self-absorption by the band narrowing

(Supplementary Table 7). The inset shows the photoluminescence intensity increasing by +40% at below 100 K, which corresponds to an increment of the quantum yield up to ~0.60. This

enhancement is larger than that expected considering the corresponding increment of the emission lifetime (Fig. 3b, inset). These findings suggest that additional temperature-dependent

ultrafast quenching pathways of diffusing charges or molecular excitons are involved in the partial emission quenching36. The presence of traps is supported by the variable-temperature

radioluminescence experiments. The radioluminescence spectrum changes in accordance with the photoluminescence (Fig. 3c and Supplementary Table 7). On the other hand, the radioluminescence

intensity—corrected by the photoluminescence behaviour (inset of Fig. 3b) to point out the intrinsic luminescence dependence on the temperature—is progressively reduced by a factor two at 10

 K. This is a fingerprint of the presence of trapping sites, which compete with the recombination of diffusing free charges on emissive ligands. Thermal energy can free the trapped charges

to be recovered for light generation reaching a thermal equilibrium (Supplementary Fig. 33)37,38, but at low temperatures they are lost with a reduction of the emission intensity. The trap

role in scintillation is investigated by wavelength-resolved thermally stimulated luminescence (TSL) measurements (Methods)39,40,41. The smooth TSL glow curve—obtained by integrating the

wavelength-resolved TSL spectra in the whole emission region—demonstrates the existence of a broad distribution of trap sites with different energy depths (Fig. 3d), which do not seriously

affect the scintillation yield of the MOFs (Supplementary Fig. 34). RADIOACTIVE GAS DETECTION WITH MOF POWDERS The capability of porous Hf-DPA to adsorb argon, krypton, xenon and radon at

room temperature and concentrate their radioactive isotopes for detection was demonstrated by combined experimental and simulated approaches. Figure 4a shows the adsorption isotherms

calculated by Grand Canonical Monte Carlo (GCMC) simulations (Methods and Supplementary Section 6). They successfully reproduce the experimental isotherms for argon and krypton,

demonstrating the validity of the developed modelling as a predictive tool (Supplementary Figs. 35and 36). The simulated adsorption at a given pressure shows a correlation between the amount

of gas adsorbed and the atomic mass, with a preference for the heavier radon. The smaller gases such as krypton are more homogenously distributed in all of the available space (Fig. 4b,

left), whereas the larger radon atom is preferably hosted in the smaller tetrahedral cavities of the MOF (Fig. 4b, right), due to the more effective interactions between the gas molecules

and the framework walls. The gas–matrix interaction energies (Supplementary Figs. 37and 38) give insight into the affinity and retention capability of the framework towards the exploring

gases (Fig. 4c), and have relevance for selectivity and detection applications in air. The gas diffusion modelled in the presence of air at room temperature indicates that krypton atoms

pervade the entire MOF crystals within tens of microseconds, demonstrating that noble gas radionuclides could be rapidly adsorbed into the pores in standard working conditions (Supplementary

Figs. 39 and 40). The Hf-DPA has been tested using a radioactive krypton isotope (85Kr) in a custom-made prototype device (Supplementary Fig. 41). The β-decay of 85Kr produces electrons

with a maximum emission energy of 687.1 keV and an average energy of 251.4 keV (ref. 42). The radionuclide can be mixed in air at different concentrations to tune the activity of the sample.

The scintillation is detected by employing a time coincidence measurement technique based on the simultaneous use of two photomultiplier tubes (PMTs) (Fig. 1b, see Methods, Supplementary

Section 11 and Supplementary Fig. 41)18. The technique can be applied using different coincidence windows to maximize the device’s sensitivity43,44,45. Here we tested a coincidence window of

40 ns (as used with liquid scintillators) and 400 ns. Figure 4d shows the results obtained for detecting 85Kr using a standard scintillating powder—that is, dye-doped polystyrene

microspheres with diameters of 175 ± 75 µm (ref. 46)—and Hf-DPA. The data highlights an improved behaviour for porous crystals. First, Hf-DPA generates a scintillation intensity ~4.6- and

3.9-times higher than microspheres for 40 ns and 400 ns coincidence windows, respectively. This demonstrates the efficiency of Hf-DPA as a scintillator despite its intrinsic lower density

(∼0.65 g cm−3) compared with polystyrene (1.02 g cm−3). Notably, gas detection can be performed with extremely high reproducibility (±1.3% for 40 ns and ±2.5% for 400 ns coincidence windows,

respectively). Moreover, the polystyrene emission peaked at 420 nm (Supplementary Fig. 31), wherein the PMTs detection efficiency (0.43) is higher than for the 490 nm MOF emission (0.25)47.

A further improvement of the detection efficiency can therefore be envisaged by matching the scintillator and photodetector properties. Second, the expected increment using a longer

coincidence window is less pronounced for Hf-DPA (around +25%) than for the polystyrene (around +50%). This indicates that MOFs work better as fast scintillators with a negligible slow

emission contribution, giving a response closer to the ideal time-independent behaviour. Third, the maximum scintillation signal is reached with slower kinetics for MOFs than polystyrene.

The signal rise time—calculated as the time employed to reach 90% of the maximum plateau—is ~600 s for Hf-DPA versus ~100 s for microspheres. A similar effect is observed when removing the

radionuclides from the sample by purging with clean air. The scintillation switches off in 800 s for MOFs, whereas it takes half of the time for the polystyrene microspheres. These findings

suggest that, in addition to the fast, automatic filling of interparticle space within packed microspheres, the radionuclides are adsorbed within the MOF pores, in agreement with the

experimental and simulated adsorption tests, thus promoting the interaction of the β-radiation with the scintillators that results in a better performance. The versatility of our approach

was demonstrated by testing Hf-DPA crystals as detectors with other radionuclides of interest, namely 222Rn (with its four decay daughters at the equilibrium, which are α- and high-energy

β-emitters) and 3H (Supplementary Figs. 41 and 42). Considering the larger capture of radon in the pores, the scintillation output should be improved with respect to krypton. Indeed, the

detection efficiency is enhanced twentyfold with respect to polystyrene (Fig. 4f). Even for the elusive tritium, the MOF powder shows a better sensitivity in the detection counting

rate—double that of polystyrene (Supplementary Fig. 43). This is a very important result as 3H is one of the most difficult gas atoms to detect, given the relatively low energy of the

β-radiation emitted with an average value of 5.7 keV (ref. 42). Regarding krypton, we further tested the device as a function of the activity of the sample, as a progressively greater number

of sensitive detectors is required. As shown in Fig. 4e, we detected 85Kr from an initial activity of 21 kBq m−3, down to 0.3 kBq m-3—two orders of magnitude lower. The instrumental

response is linear with the sample activity, suggesting the possibility of setting highly accurate calibrations of devices to detect ultralow activity levels. Notably, we successfully

detected an activity below the minimum value declared for commercial 85Kr detectors (vertical lines in Fig. 4e), in a device much smaller in size, with less volume of monitored gas and using

one-order-of-magnitude-shorter acquisition times (Methods and Supplementary Section 11), owing to the porous scintillator’s ability to adsorb the gas48,49. These remarkable results

demonstrate that the prototype device presented here, although in its embryonal form, displays better sensitivity than state-of-the-art devices and highlights the technological advantage of

potentially using compact, easy-to-handle and cheaper devices. Considering the good stability of Hf-DPA that does not imply any critical storage protocol (Supplementary Table 9 and

Supplementary Fig. 45), this work strongly supports the development of radioactive gas detectors based on porous MOF crystals as scintillators that can overcome current technological

limitations. DISCUSSION In summary, we designed and fabricated specific scintillating porous MOF crystals to detect radioactive noble gases. Their good luminescence and scintillation

properties—combined with their characteristic porosity—allowed us to realize a fully operative prototype detector. An intensive study on a broad range of critical β-emitting radioactive

gases was performed, namely, the low-energy β-emitter 3H, the high-energy β-emitter 85Kr, and the β/α-emitter 222Rn. The MOF crystals exhibited improved performance compared with commercial

powder-like materials currently tested, and we found that 85Kr can be detected with excellent sensitivity down to radioactivity values below the limit of commercial systems. The obtained

results are therefore stimulating not only from the scientific point of view, as radionuclide detection using porous scintillators has been demonstrated here for the first time, but also

from the technological perspective, hinting at a potential breakthrough by developing conceptually new optimized universal devices that allow detecting all the gas radionuclides species of

interest. In this regard, it is worth pointing out that MOF powders cannot easily be used in the present form due to the practical problems of handling, especially from the perspective of

industrial production. We are thus working on the realization of a hierarchical porous architecture in which porous MOFs are homogenously distributed in a porous polymeric host endowed with

mesopores and macropores suitable for gas diffusion. In such a configuration, the MOFs will be employed to further concentrate and detect the radionuclides, thus realizing the first example

of composite bulk porous scintillators for radioactive gas detection. Similarly, the instrumental design will be improved to get a more functional device. A possible evolution can be the use

of a cylindrical shape container for the porous scintillator with aerosol filters as the entrance and exit face, in which the gas flow would circulate freely through the whole porous

material, placed vertically between two photomultipliers. In such a configuration, the gas flow will be orthogonal to the detection line while diffusing through the whole scintillator, thus

maximizing the radionuclide accumulation and the scintillation detection yield. The combination of easy-to-handle hierarchical porous scintillators and excellent detection properties of

porous MOFs with an optimized instrumental design will provide a pivotal step forward in the fabrication of high-tech ultrasensitive and reusable detectors, especially for low-energetic

radionuclides such as tritium produced in nuclear plants. METHODS SYNTHESIS OF HF-DPA CRYSTALS Hf-DPA crystals were synthesized using modulated solvothermal condition. Briefly,

9,10-bis(4-carboxyphenyl) anthracene (209.0 mg; 0.5 mmol) and HfCl4 (160.0 mg; 0.5 mmol) were added to a 100 ml pyrex bottle with cleavable teflon-lined cap. Dry DMF (50 ml) and 400 µl of

formic acid were added and the bottle was closed and sonicated for 60 s to obtain a well-dispersed mixture. The mixture was heated at 120 °C for 22 h in a preheated oven. The glass bottle

was then removed from the oven and cooled to room temperature. The yellowish solid was collected by filtration on a 0.2 µm PTFE membrane and washed with DMF (3 × 100 ml) and then CHCl3 (3 × 

100 ml). The powder was recovered and dried at 120 °C under high vacuum before further analysis. Yield: 178 mg (58%) (see the Supplementary Information for further details on ligand and MOF

preparation). HF-DPA ANALYSIS AND CHARACTERIZATIONS Powder X-ray diffraction patterns were collected on a Rigaku Smartlab using Cu-Kα radiation, whereas synchrotron radiation powder X-ray

diffraction was performed at the ESRF ID22 beam line using a wavelength of 0.354 Å. The crystal structure was refined by the Rietveld method combined with molecular mechanics and plane-wave

density functional theory calculations (Supplementary Section 5). The structure data are available at the Cambridge Crystallographic Data Centre repository, deposition no. 2218565. The

composition of Hf-DPA was studied by means of NMR spectroscopy in solution, solid-state NMR spectroscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, scanning

electron microscopy and EDS analysis. The gas sorption properties were investigated collecting nitrogen, argon and krypton adsorption isotherms at 77 K up to saturation pressure and argon

and krypton at 298 K; hyperpolarized 129Xe NMR experiments were performed by a home-built apparatus with a continuous-flow delivery of hyperpolarized xenon gas with a Bruker Avance 300

spectrometer operating at a Larmor Frequency of 83.02 MHz for 129Xe. The xenon and radon adsorption isotherms at 298 K were performed by GCMC. PHOTOLUMINESCENCE STUDIES Absorption spectra

were recorded using a Cary Lambda 900 spectrophotometer at normal incidence with Suprasil quartz cuvettes with a 0.1 cm optical path length and an integrating sphere to eliminate scattering

effects. Steady-state photoluminescence spectra were acquired using a Varian Eclipse fluorimeter (bandwidth 1 nm) using quartz cuvettes of 0.1 cm optical path length. Time-resolved

photoluminescence spectra of the MOFs dispersions were recorded by monitoring the emission decay of the samples at 435 nm. The MOFs were excited with a pulsed light-emitting diode at 340 nm

(3.65 eV, pulse width 80 ps; EP-LED 340, Edinburgh Instruments). The MOFs were excited with a pulsed laser at 405 nm (3.06 eV, pulse width 90 ps; EPL-405, Edinburgh Instruments) to avoid

direct excitation of the host polymer matrix. photoluminescence decay times were measured at the maximum of the emission spectrum. Relative and absolute photoluminescence quantum yields were

measured with different methods as described in the Supplementary Section 7. For experiments at cryogenic temperatures, the samples were excited by a frequency tripled pulsed Nd:YAG laser

source at 3.49 eV (355 nm) operated at 10 kHz; the emitted light was collected using a custom apparatus featuring a liquid nitrogen-cooled, back-illuminated, and ultraviolet-enhanced

charge-coupled device detector (Jobin-Yvon Symphony II) coupled to a monochromator (Jobin-Yvon Triax 180) equipped with a 100 lines per millimetre grating. RADIOLUMINESCENCE AND

SCINTILLATION STUDIES The samples were excited by unfiltered X-ray irradiation using a Philips PW2274 X-ray tube, with a tungsten target, equipped with a beryllium window and operated at 20 

kV. At this operating voltage, X-rays are produced by the _Bremsstrahlung_ mechanism, superimposed to the L and M transition lines of tungsten due to the impact of electrons generated

through a thermionic effect and accelerated onto the tungsten target. Cryogenic radioluminescence measurements are performed in the 10−370 K interval. Radioluminescence has been recorded on

powder samples of 1 mm thickness in an aluminium sample holder. For comparison the radioluminescence spectra has been normalized by the mass of the investigated powder. Scintillation has

been recorded under pulsed X-rays with energies up to 25 keV generated with a repetition rate of 1 MHz by a picosecond diode laser at 405 nm (Delta diode from Horiba) focused on an X-ray

tube (model N5084 from Hamamatsu). The resulting photons were collected by Kymera spectrograph (ANDOR) and detected by a hybrid PMT 140-C from Becker and Hickl GmbH. For decay-time

measurements, the photons were histogramed using a PicoHarp300 time-correlated single-photon counting (32 ps time per bin) and for the time resolved spectra a MCS6A multiple-channel time

analyzer was used (800 ps time per bin). Subnanosecond scintillation emission kinetics of the samples were measured with a time-correlated single-photon counting set-up. THERMALLY STIMULATED

LUMINESCENCE MEASUREMENTS Wavelength-resolved TSL at cryogenic temperatures is performed by using the same detection system as for radioluminescence measurements. Cryogenic TSL measurements

are performed in the 10−320 K interval, with a linear heating rate of 0.1 K s–1, after X-ray irradiation up to around 10 Gy. The dose values for X-ray irradiations were calibrated with an

ionization chamber in air. RADIOACTIVE GAS DETECTION EXPERIMENTS The experiments are performed using a unique gas bench developed at the CEA, Paris-Saclay, and by allowing the production of

radioactive gas atmospheres using high activity standards50. Different sampling and dilution steps allow for precise control of the injected activity, and precise knowledge of the volumetric

activity of each gas: at best, the relative standard uncertainty on the activity concentration is 0.4%, 0.6% and 0.8% for 222Rn, 85Kr and 3H, respectively (Supplementary Table 9). For each

experiment, the same type of three step sequence is performed. First, the measurement of the blank, by circulating clean air without additional radioactivity. Second, the measurement of

scintillation by circulating the radioactive gas sample into the vial (4 mm diameter and 50 mm height, 0,1086 g for Hf-DPA and 0.3640 for polystyrene microspheres, activity 10 kBq). Third,

circulation of clean air into the device to remove the radioactive gas. The light photons produced by scintillation are measured using a metrological device developed to exploit the

triple-to-double coincidence ratio (Supplementary Fig. 41)18, with a specific connection cap adapted to the radioactive gas flow in the scintillator. DATA AVAILABILITY The data that support

the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request, at the public repository of the project SPARTE FET Open

Project (https://www.sparte-project.eu/). The Hf-DPA structure’s Cambridge Crystallographic Data Centre deposition no. is 2218565. No custom code has been developed for computational

modeling and simulations. REFERENCES * Bollhöfer, A. et al. Half a century of Krypton-85 activity concentration measured in air over Central Europe: trends and relevance for dating young

groundwater. _J. Environ. Radioact._ 205–206, 7–16 (2019). Article  Google Scholar  * Zeng, J. et al. Development of a well-type phoswich detector for low concentration krypton-85

measurement. _Nucl. Instrum. Methods Phys. Res. A_ 1013, 165634 (2021). Article  Google Scholar  * Huang, Y.-J. et al. Automated separation and analysis of krypton-85 from low-volume gaseous

effluent of nuclear power plant. _J. Radioanal. Nucl. Chem._ 323, 213–222 (2020). Article  Google Scholar  * Aoyama, M. Long-term behavior of 137Cs and 3H activities from TEPCO Fukushima

NPP1 accident in the coastal region off Fukushima, Japan. _J. Radioanal. Nucl. Chem._ 316, 1243–1252 (2018). Article  Google Scholar  * Cao, Y. et al. Long-term investigation of

environmental radioactivity levels and public health around the Qinshan Nuclear Power Plant, China. _Sci. Rep._ 12, 4945 (2022). Article  ADS  Google Scholar  * Schoeppner, M. & Glaser,

A. Present and future potential of krypton-85 for the detection of clandestine reprocessing plants for treaty verification. _J. Environ. Radioact._ 162-163, 300–309 (2016). Article  Google

Scholar  * _Comprehensive Nuclear-Test-Ban Treaty Organization_ (CTBTO, 2022);https://www.ctbto.org/ * Ćujić, M. et al. Radon-222: environmental behavior and impact to (human and non-human)

biota. _Int. J. Biometeorol._ 65, 69–83 (2021). Article  ADS  Google Scholar  * Abd Elkader, M. M., Shinonaga, T. & Sherif, M. M. Radiological hazard assessments of radionuclides in

building materials, soils and sands from the Gaza Strip and the north of Sinai Peninsula. _Sci. Rep._ 11, 23251 (2021). Article  ADS  Google Scholar  * Rudin, C. M., Brambilla, E.,

Faivre-Finn, C. & Sage, J. Small-cell lung cancer. _Nat. Rev. Dis. Primers_ 7, 3 (2021). Article  Google Scholar  * Kissane, J., Neutze, J. A. & Singh, H. _Radiology Fundamentals:

Introduction to Imaging and Technology_ (Springer, 2020). * Camfferman, F. A. et al. Diagnostic and predictive value of Doppler ultrasound for evaluation of the brain circulation in preterm

infants: a systematic review. _Pediatr. Res._ 87, 50–58 (2020). Article  Google Scholar  * Nichols, A. L. Status of the decay data for medical radionuclides: existing and potential

diagnostic γ emitters, diagnostic β+ emitters and therapeutic radioisotopes. _Radiochim. Acta_ 110, 609–644 (2022). Article  Google Scholar  * _European Union EURATOM Directive 59/2013

‘Basic Safety Standards'_ (European Union, 2013); https://eur-lex.europa.eu/eli/dir/2013/59/oj * _Legislative Decree of 31 July 2020, no. 101 of Implementation of the Directive

2013/59/EURATOM of the European Council_ (Ispettorato Nazionale per la Sicurezza Nucleare e la Radioprotezione, 2020);

https://www.isinucleare.it/en/radiation-protection-and-environmental-radioactivity * Aprile, E., Bolotnikov, A. E., Bolozdynya, A. I. & Doke, T. _Noble Gas Detectors_ (John Wiley and

Sons, 2006). * Li, X. et al. Simultaneous determination of gross alpha/beta activities in water by liquid scintillation counting and its applications in the environmental monitoring. _Sci.

Rep._ 12, 8281 (2022). Article  ADS  Google Scholar  * Sabot, B., Dutsov, C., Cassette, P. & Mitev, K. Performance of portable TDCR systems developed at LNE-LNHB. _Nucl. Instrum. Methods

Phys. Res. A_ 1034, 166721 (2022). Article  Google Scholar  * Eddaoudi, M., Li, H. & Yaghi, O. Highly porous and stable metal−organic frameworks: structure design and sorption

properties. _J. Am. Chem. Soc._ 122, 1391–1397 (2000). Article  Google Scholar  * Kitagawa, S., Kitaura, R. & Noro, S. I. Functional porous coordination polymers. _Angew. Chem. Int. Ed._

43, 2334–2375 (2004). Article  Google Scholar  * Férey, G. Hybrid porous solids: past, present, future. _Chem. Soc. Rev._ 37, 191–214 (2008). Article  Google Scholar  * Mezenov, Y. A.,

Krasilin, A. A., Dzyuba, V. P., Nominé, A. & Milichko, V. A. Metal–organic frameworks in modern physics: highlights and perspectives. _Adv. Sci._ 6, 1900506 (2019). Article  Google

Scholar  * Elsaidi, S. K. et al. Radiation-resistant metal–organic framework enables efficient separation of krypton fission gas from spent nuclear fuel. _Nat. Commun._ 11, 3103 (2020).

Article  ADS  Google Scholar  * Jin, K., Lee, B. & Park, J. Metal–organic frameworks as a versatile platform for radionuclide management. _Coord. Chem. Rev._ 427, 213473 (2021). Article

  Google Scholar  * Lustig, W. P. et al. Metal–organic frameworks: functional luminescent and photonic materials for sensing applications. _Chem. Soc. Rev._ 46, 3242–3285 (2017). Article 

Google Scholar  * Doty, F., Bauer, C., Skulan, A., Grant, P. & Allendorf, M. Scintillating metal–organic frameworks: a new class of radiation detection materials. _Adv. Mater._ 21,

95–101 (2009). Article  Google Scholar  * Perego, J. et al. Composite fast scintillators based on high-_Z_ fluorescent metal–organic framework nanocrystals. _Nat. Photon._ 15, 393–400

(2021). Article  ADS  Google Scholar  * Perego, J. et al. Highly luminescent scintillating hetero-ligand MOF nanocrystals with engineered Stokes shift for photonic applications. _Nat.

Commun._ 13, 3504 (2022). Article  ADS  Google Scholar  * Shi, W. et al. Advances of metal organic frameworks in analytical applications. _Mater. Today Adv._ 15, 100273 (2022). Article 

Google Scholar  * Yang, G. L., Jiang, X. L., Xu, H. & Zhao, B. Applications of MOFs as luminescent sensors for environmental pollutants. _Small_ 17, 2005327 (2021). Article  Google

Scholar  * Sozzani, P. et al. Nanoporosity of an organo-clay shown by hyperpolarized xenon and 2D NMR spectroscopy. _Chem. Commun_. 1921–1923 (2006). * Comotti, A., Bracco, S., Valsesia, P.,

Ferretti, L. & Sozzani, P. 2D Multinuclear NMR, hyperpolarized xenon and gas storage in organosilica nanochannels with crystalline order in the walls. _J. Am. Chem. Soc._ 129, 8566–8576

(2007). Article  Google Scholar  * Bassanetti, I. et al. Flexible porous molecular materials responsive to CO2, CH4 and Xe stimuli. _J. Mater. Chem. A_ 6, 14231–14239 (2018). Article 

Google Scholar  * Comotti, A. et al. Fluorinated porous organic frameworks for improved CO2 and CH4 capture. _Chem. Commun._ 55, 8999–9002 (2019). Article  Google Scholar  * Monguzzi, A. et

al. Highly fluorescent metal–organic-framework nanocomposites for photonic applications. _Nano Lett._ 18, 528–534 (2018). Article  ADS  Google Scholar  * Ding, T. X., Olshansky, J. H.,

Leone, S. R. & Alivisatos, A. P. Efficiency of hole transfer from photoexcited quantum dots to covalently linked molecular species. _J. Am. Chem. Soc._ 137, 2021–2029 (2015). Article 

Google Scholar  * Korzhik, M., Tamulaitis, G. & Vasil’ev, A. N. _Physics of Fast Processes in Scintillators_. Vol. 262 (Springer, 2020). * Guerassimova, N., Garnier, N., Dujardin, C.,

Petrosyan, A. & Pedrini, C. X-ray excited charge transfer luminescence of ytterbium-containing aluminium garnets. _Chem. Phys. Lett._ 339, 197–202 (2001). * McKeever, S. W. S.

_Thermoluminescence of Solids_ (Cambridge Univ. Press, Cambridge 1985). * Vedda, A. et al. Trap-center recombination processes by rare earth activators in YAlO3 single crystal host. _Phys.

Rev. B_ 80, 045113 (2009). Article  ADS  Google Scholar  * Buryi, M. et al. Trapping and recombination centers in cesium hafnium chloride single crystals: EPR and TSL study. _J. Phys. Chem.

C_ 123, 19402–19411 (2019). Article  Google Scholar  * Bé, M.-M. et al. _Table of Radionuclides (Vol. 3 – A = 3 to 244_) (International Bureau of Weights and Measures, 2006). * Dutsov, C.,

Cassette, P., Mitev, K. & Sabot, B. In quest of the optimal coincidence resolving time in TDCR LSC. _Nucl. Instrum. Methods Phys. Res. A_ 987, 164846 (2021). Article  Google Scholar  *

Dutsov, C., Cassette, P., Sabot, B. & Mitev, K. Evaluation of the accidental coincidence counting rates in TDCR counting. _Nucl. Instrum. Methods Phys. Res. A_ 977, 164292 (2020).

Article  Google Scholar  * Dutsov, C., Sabot, B., Cassette, P. & Mitev, K. Significance of the corrections for accidental coincidences in liquid scintillation counting measurements. _J.

Radioanal. Nucl. Chem._ 331, 3303–3311 (2022). Article  Google Scholar  * Santiago, L. M., Bagán, H., Tarancón, A. & Garcia, J. F. Synthesis of plastic scintillation microspheres:

evaluation of scintillators. _Nucl. Instrum. Methods Phys. Res. A_ 698, 106–116 (2013). Article  ADS  Google Scholar  * _R7600U PMT_ (Hamamtsu Photonics, 2022). * _FHT 59 E Noble Gas

Monitor_ (Thermo Scientific, 2022). * _XPR80_ (Mirion Technologies, 2022). * Sabot, B., Rodrigues, M. & Pierre, S. Experimental facility for the production of reference atmosphere of

radioactive gases (Rn, Xe, Kr, and H isotopes). _Appl. Radiat. Isot._ 155, 108934 (2020). Article  Google Scholar  Download references ACKNOWLEDGEMENTS We acknowledge support from the

European Community through the grant no. 899293, HORIZON 2020—SPARTE FET OPEN. Financial support from the Italian Ministry of University (MUR) through grant no. PRIN 2020—SHERPA no.

H45F2100343000, and from Lombardy Region through the ‘Enhancing photosynthesis’ award, no. H45F21002830007. We thank the ESRF synchrotron facility in Grenoble (France) for access to the ID22

beamline (project no. HC-4781). AUTHOR INFORMATION Author notes * These authors contributed equally: Matteo Orfano, Jacopo Perego. AUTHORS AND AFFILIATIONS * Dipartimento di Scienza dei

Materiali, Università degli Studi Milano-Bicocca, Milan, Italy Matteo Orfano, Jacopo Perego, Francesca Cova, Charl X. Bezuidenhout, Sergio Piva, Silvia Bracco, Anna Vedda, Angiolina Comotti 

& Angelo Monguzzi * Institut Lumière Matière, Université Claude Bernard Lyon, Lyon, France Christophe Dujardin & Pavlo Mai * Université Paris-Saclay, CEA, LIST, Laboratoire National

Henri Becquerel (LNE-LNHB), Palaiseau, France Benoit Sabot & Sylvie Pierre * Nano Active Film SRL, Dipartimento di Chimica e Biologia, Università degli Studi di Salerno, Fisciano, Italy

Christophe Daniel Authors * Matteo Orfano View author publications You can also search for this author inPubMed Google Scholar * Jacopo Perego View author publications You can also search

for this author inPubMed Google Scholar * Francesca Cova View author publications You can also search for this author inPubMed Google Scholar * Charl X. Bezuidenhout View author publications

You can also search for this author inPubMed Google Scholar * Sergio Piva View author publications You can also search for this author inPubMed Google Scholar * Christophe Dujardin View

author publications You can also search for this author inPubMed Google Scholar * Benoit Sabot View author publications You can also search for this author inPubMed Google Scholar * Sylvie

Pierre View author publications You can also search for this author inPubMed Google Scholar * Pavlo Mai View author publications You can also search for this author inPubMed Google Scholar *

Christophe Daniel View author publications You can also search for this author inPubMed Google Scholar * Silvia Bracco View author publications You can also search for this author inPubMed 

Google Scholar * Anna Vedda View author publications You can also search for this author inPubMed Google Scholar * Angiolina Comotti View author publications You can also search for this

author inPubMed Google Scholar * Angelo Monguzzi View author publications You can also search for this author inPubMed Google Scholar CONTRIBUTIONS M.O., F.C., A.V. and A.M. conceived and

performed the photoluminescence, radioluminescence experiments. J.P., C.X.B., S.P., C.Da. and S.B. A.C. designed, synthesized and characterized the MOFs. C.Du. managed the scintillation

experiments. B.S., S. P. and P.M. designed, performed and analyzed the gas detection experiments. C.Du., B.S., A.C. and AM. conceived the project and wrote the paper. A.C. and AM. wrote the

paper. All of the authors agreed to all of the content of the manuscript, the author list and its order, and the author contribution statements. Any changes to the author list after

submission will be subject to approval by all authors. CORRESPONDING AUTHORS Correspondence to Anna Vedda, Angiolina Comotti or Angelo Monguzzi. ETHICS DECLARATIONS COMPETING INTERESTS The

authors declare no competing interests. PEER REVIEW PEER REVIEW INFORMATION _Nature Photonics_ thanks Wei Chen, Wolfgang Heiss and the other, anonymous, reviewer(s) for their contribution to

the peer review of this work. ADDITIONAL INFORMATION PUBLISHER’S NOTE Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

SUPPLEMENTARY INFORMATION SUPPLEMENTARY INFORMATION Supplementary Methods, Figs. 1–45, Tables 1–9 and details. RIGHTS AND PERMISSIONS OPEN ACCESS This article is licensed under a Creative

Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the

original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in

the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended

use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit

http://creativecommons.org/licenses/by/4.0/. Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Orfano, M., Perego, J., Cova, F. _et al._ Efficient radioactive gas detection by

scintillating porous metal–organic frameworks. _Nat. Photon._ 17, 672–678 (2023). https://doi.org/10.1038/s41566-023-01211-2 Download citation * Received: 15 November 2022 * Accepted: 07

April 2023 * Published: 18 May 2023 * Issue Date: August 2023 * DOI: https://doi.org/10.1038/s41566-023-01211-2 SHARE THIS ARTICLE Anyone you share the following link with will be able to

read this content: Get shareable link Sorry, a shareable link is not currently available for this article. Copy to clipboard Provided by the Springer Nature SharedIt content-sharing

initiative