Humidity sensors based on porous materials have demonstrated broad application prospects in the field of relative humidity (RH) monitoring due to their unique advantages. In this work, a high-performance resistance-type humidity sensor was successfully fabricated using the MOF-type humidity-sensitive material AlFFIVE-1-Ni. Systematic studies reveal that the straight-through and ordered pore structure, abundant fluorine (F) atoms, and open metal sites (Ni2+) inherent in the AlFFIVE-1-Ni endow it with exceptional hydrophilicity and excellent cycling stability. Benefiting from these features, the AlFFIVE-1-Ni-based humidity sensor exhibits outstanding sensing performance. For instance, within the low-frequency range (40-100 Hz), the total impedance modulus of the AlFFIVE-1-Ni-based sensor changes by more than two orders of magnitude over the RH interval of 11-95%, demonstrating its ability to generate a highly sensitive response to humidity variations across a wide humidity range. Meanwhile, above 33% RH, the sensor shows a good linear correlation between impedance modulus and RH, confirming the reliability and consistency of its response under different humidity levels. Impressively, the AlFFIVE-1-Ni-based humidity sensor exhibits rapid response-recovery speeds (6 s/3 s), low hysteresis (3% RH), and excellent long-term stability across a wide RH range (11-95%). Furthermore, the intrinsic mechanism underlying the exceptional sensing performance of the AlFFIVE-1-Ni-based sensor has been thoroughly elucidated through complex impedance curve (CIC) and equivalent circuit (EC) analysis, density functional theory (DFT) calculations, and Grand Canonical Monte Carlo (GCMC) simulations. These results collectively highlight the tremendous potential of the AlFFIVE-1-Ni-based humidity sensor for highly sensitive and rapid RH detection.

Ammonia (NH3), as a crucial industrial raw material, is widely utilized in various fields such as industry and agriculture. However, the accompanying environmental pollution and health risks have become increasingly prominent. Therefore, the development of high-performance adsorbent materials for NH3 separation and storage has emerged as a key research focus in materials science. Herein, a composite adsorbent material (denoted as NiCl2@XJCOF-2) with efficient NH3 capture performance was prepared by integrating NiCl2 into a zwitterionic covalent organic framework (XJCOF-2). This adsorbent exhibits a high NH3 uptake capacity of 30.3 mmol center dot g(-1) at 298 K and 1.0 bar. Notably, it achieves a record-high capacity of 23.4 mmol center dot g(-1) at low pressure of 0.03 bar and demonstrates with exceptional IAST selectivity (all >10(7)) for NH3/CO2, NH3/N-2, and NH3/H-2, highlighting its remarkable potential for trace ammonia removal. Theoretical calculations reveal that the cationic and anionic groups within the zwitterionic XJCOF-2 effectively promote the dispersion and dissociation of NiCl2, serving as an excellent "solid-state solvent." Benefiting from the abundant exposed Ni2+ sites and sulfonate groups within the pores of XJCOF-2, which can strongly interact with NH3 through dual effects mediated by coordination and hydrogen bonding, thereby endowing NiCl2@XJCOF-2 with both high-capacity adsorption and high selectivity for NH3.

Xenon (Xe) recovery from nuclear off-gas (0.04% Xe) is valuable but challenging for single-technology methods to achieve both high recovery and purity. This study proposes a novel integrated process that couples a dual-stage vacuum pressure swing adsorption (VPSA) system with cryogenic distillation for efficient Xe recovery with high recovery and ultra-purification. Experimentally determined adsorption data on H-ZSM-5 zeolite informed the simulation. The dual-stage VPSA processes consist of a stripping reflux VPSA stage for flow reduction and pre-concentration of Xe, a dual reflux VPSA stage for Xe deep purification, and cryogenic distillation unit for final purification of Xe. Simulation results demonstrate that under optimized conditions, the integrated system achieves an overall Xe recovery of 98.70% and a Xe product purity >99.998%, And the specific energy consumption of xenon produced in the optimized integrated process is 489.56 MJ/kg Xe. This integrated strategy effectively overcomes the limitations of single separation technologies and provides a reliable technical pathway for recovering high-value components from nuclear off-gas and similar dilute gas streams with low energy consumption.

Sulfur dioxide (SO2), a typical industrial byproduct and hazardous pollutant, requires efficient capture for environmental protection and resource recovery. However, existing adsorbents face challenges such as unsatisfactory selectivity and performance degradation at elevated temperatures in complex flue gas environments. This study presents the judicious construction of isostructural metal-organic frameworks (MOFs) (Cu-L, Cu-L-FA, Cu-L-BA) using a pyrazine tetracarboxylate linker and copper ions, with formic/benzoic acid modulators retained to fine-tune adsorption performance. The resulting MOFs exhibit a rare 4,4-connected mfj topology. These isostructural Cu-L variants demonstrate substantial SO2 uptake capacity and performance retention at relatively high temperatures. Notably, the formate-modulated variant (Cu-L-FA) achieves an SO2 adsorption capacity of 4.5 mmol·g-1 at 298 K and 1 bar, and retains 97% of its capacity at 313 K, significantly outperforming conventional physisorbents. Mechanistic studies reveal that the adsorption process is governed by reversible coordination to Cu(II) sites and multifaceted interactions with basic pyrazine nitrogen atoms. The incorporation of modulators not only optimizes the trade-off between adsorption and regeneration energy but also triggers SO2-induced dynamic modulator-node interactions, leading to instant high SO2 uptake at low pressures and enhanced cooperative adsorption. This work provides a novel strategy for designing SO2 adsorbents with salient performance for flue gas desulfurization.

The removal of trace neon from helium represents a critical bottleneck in the production of ultrahigh-purity helium, which is indispensable for advanced technologies such as semiconductor manufacturing and cryogenics. Existing adsorbents suffer from either low selectivity or insufficient capacity under practically viable cryogenic conditions, often necessitating energy-intensive processes below 50 K. Herein, we report an ultramicroporous metal-organic framework, UTSA-280, that enables highly efficient Ne/He separation at the industrially accessible temperature of liquid nitrogen (77 K). UTSA-280 features rigid 1D channels with tailored aperture sizes (3.2 & times; 4.5 and 3.8 & times; 3.8 & Aring;2) and a polarized electrostatic environment arising from Ca2+ centers and squaric acid ligands, which can achieve a record Ne/He selectivity of 1602 and an exceptional Ne uptake of 5.419 mmol & centerdot;g-1 at 77 K and 100 kPa. Breakthrough experiments and process simulations confirm its ability to produce high-purity helium directly from a Ne/He (0.1/99.9) mixture, providing an energy-efficient and scalable strategy to address the growing demand for ultra-pure helium in electronic and cryogenic applications.

ABSTRACT The separation of Kr/Xe from spent nuclear fuel off‐gas is critical, yet most current adsorbents exhibit Xe‐Kr co‐adsorption under elevated pressures, posing challenges for industrial pressure swing adsorption processes. Herein, we present and evaluate a metal‐organic framework, CALF‐20M‐w, engineered for molecular sieving separation of Kr/Xe under industrial pressure conditions. CALF‐20M‐w possesses a pore size of 3.7 Å, which position between Kr (3.6 Å) and Xe (4.1 Å) kinetic diameters, enables record Kr/Xe uptake ratio (52.2) and selectivity of 4424 at 195 K and 5 bar, surpassing all benchmark materials. GCMC simulations reveal that Kr atoms occupy favorable positions within CALF‐20M‐w's intersecting channels, while Xe atoms are sterically excluded in the pressure range of 1–30 bar. Dynamic breakthrough separation experiments and PSA simulation show CALF‐20M‐w can yield >99.9% pure Xe, demonstrating feasibility for radioactive Kr removal from spent nuclear fuel off‐gases. Moreover, CALF‐20M‐w exhibits extreme radiation resistance under β‐irradiation (72 kGy/h) and γ‐irradiation (240 kGy), outperforming UiO‐66 and ZIF‐8. CALF‐20M‐w sets new benchmarks for high‐pressure molecular sieving in Kr/Xe separation, offering a highly promising strategy for nuclear waste management and rare gas purification.

Deep removal of trace Ne from He feedstocks at liquid nitrogen temperature (77 K) is an important and challenging problem due to their similar molecular dimensions and weak polarizability difference. Herein, the Ne/He separation performance in fluorinated ultramicroporous metal-organic framework, KAUST-7, was systematically investigated at 77 K. KAUST-7 features narrow 3.5 Å channels lined with highly electronegative fluorine atoms, generating a localized negative electrostatic field in the confined pores. Static adsorption measurements revealed a Ne uptake of 2.95 mmol·g−1 at 77 K versus only 0.0227 mmol·g−1 for He in KAUST-7. IAST calculations predicted an exceptional Ne/He selectivity of 3.6 × 103 for a 0.1/99.9 feed, remaining 262 at 87 K. Kinetic tests demonstrated rapid Ne capture in KAUST-7, which can reach 67% of equilibrium uptake within 10 s at an initial rate of 0.198 mmol·g−1·s−1, with a kinetic selectivity of 216.05. DFT calculations yielded Ne and He binding energies in KAUST-7 was −9.92 and − 0.22 kJ·mol−1, respectively, confirming fluorine-induced polarization as the origin of selective Ne capture. Breakthrough experiments tests confirmed excellent dynamic separation performance at 77 K. This work highlights the synergistic effect of ultramicroporous confinement and fluorine-functionalized pore chemistry for ultrahigh-selectivity Ne/He separation.

Selective capture of sulfur dioxide (SO2) is of great significance in the context of environmental protection, yet it remains an ongoing challenge. To address inefficient SO2 removal from flue gas, this study synthesized a cagelike organic network (CON) and converted it into an ionic I-CON via facile quaternization modification. Solidstate 13C NMR, XPS, SEM and TEM-EDS confirmed iodine ion (I-) incorporation in I-CON, narrowing its pore size to 1.05 nm. Single-component gas adsorption experiments demonstrated that I-CON exhibits an SO2 uptake as high as 16.44 mmol/g at 298 K, surpassing that of CON (11.54 mmol/g). Furthermore, the IAST (Ideal Adsorbed Solution Theory) selectivity of I-CON for SO2/CO2 binary gas mixture also exceeded that of CON (112.10 vs 93.96). Dynamic tests showed I-CON has prolonged SO2 breakthrough time to 3592 s, indicating that the high dynamic selectivity of I-CON for SO2/CO2 and SO2/N2. DFT calculations revealed that the synergistic effect between the surface electric field-mediated induced polarization and charge transfer in I-CON significantly enhances its selective adsorption performance toward SO2. This study validates the potential of I-CON in the efficient capture of SO2.

The development of dynamically responsive soft porous crystals (SPCs) is crucial for advanced gas separation due to their stimuli-triggered structural transitions. Herein, we report a 3D covalent organic framework (FCOF-XJ) constructed from flexible tetrahedral (F-3D-Td) and rigid tetrahedral (3D-Td) building blocks, exhibiting unique temperature-dependent selective adsorption of xenon (Xe). FCOF-XJ features thermoresponsive -O-C-C-C-O- single bonds that enable temperature-dependent conformational switching. The adaptive pore structure of FCOF-XJ enables an Xe-triggered gate-opening effect, with 4 times increase of Xe adsorption and a high Xe/Kr selectivity (36.9 at 298 K, 1 bar) among porous organic materials, surpassing most of metal-organic frameworks (MOFs). Breakthrough experiments reveal a defined high-purity Xe recovery window from Xe/Kr mixtures under non-ideal dynamic conditions, enabled by thermoresponsive pore-gating dynamics. This work establishes a flexible COF platform for thermoresponsive and Xe-selective capture based on guest-triggered framework gating.

This study addresses the critical challenge of Kr coadsorption during Xe/Kr separation in rigid porous adsorbents by developing novel flexible porous adsorbents based on Tröger's Base dihedral angle structures (TBPOF-1 to TBPOF-4). These TBPOFs leverage a flexible dihedral angle that dynamically adapts to selectively capture Xe over Kr through a "recognition-resonance-capture" mechanism. The adsorbents exhibit exceptional Xe uptake capacities with negligible Kr adsorption at pressures below 0.2 bar, achieving a record IAST selectivity of 483.8 (for Xe/Kr = 50:50 at 0.01 bar with TBPOF-4). Adsorption kinetic studies reveal rapid Xe adsorption (10.4 mL g-1 s-1) compared to sluggish Kr uptake (0.10 mL g-1 s-1) in TBPOFs, yielding a kinetic selectivity of 1166. Breakthrough experiments demonstrate that TBPOFs enable one-step Xe purification without Kr coadsorption, achieving >99.9% Xe and Kr in a one-step adsorption-desorption process, even at trace Xe-Kr concentration (400 ppm Xe, 40 ppm Kr) mixed-gas flows. Density functional theory and molecular dynamics (DFT/MD) simulations elucidate the dynamic Xe "recognition-resonance-capture" mechanism of the Tröger's Base dihedral angle. This work offers a transformative strategy to design dynamic Xe recognition adsorbents for energy-efficient Xe-Kr separation.

The deep removal of sulfur dioxide (SO2) from flue gas is of significant importance for environmental protection, yet developing adsorbents with high uptake capacity and selectivity, as well as excellent cycling stability, remains a formidable challenge. Herein, two porous aromatic frameworks (PAFs) with electron-rich conjugated structures (termed PAF-TrP and PAF-SBF) were prepared for the selective capture of SO2 from flue gas. A systematic investigation involving static gas adsorption, dynamic breakthrough experiments, stability tests, and molecular-level simulations demonstrated that both PAFs exhibit an exceptional SO2 capture performance. Under conditions of 298 K and 1 bar, the uptake capacities of SO2 in PAF-TrP and PAF-SBF reach 259.1 and 344.7 cm-3·g-1, respectively. The IAST (ideal adsorbed solution theory) selectivities of PAF-TrP and PAF-SBF toward SO2 in the SO2/N2 binary gas mixture are 4159.3 ∼ 902.8 and 3769.1 ∼ 844.3, respectively, at 298 K and 1 bar. Molecular-level simulation calculations based on density functional theory (DFT) revealed the intrinsic mechanism underlying the highly selective SO2 capture by the two PAFs. Specifically, the localized charge separation on the electron-rich aromatic conjugated frameworks of both PAFs generates a gradient electric field, which induces strong dipole-dipole and dipole-π interactions with polar SO2 molecules. Additionally, the construction mode of the two PAFs via strong covalent linkages endows them with remarkable stability and favorable regenerability. This study represents a meaningful endeavor toward developing high-performance adsorbents for flue gas desulfurization.

In this work we report a novel strategy to enhance the adsorption capacity of conventional porous materials by engineering intrinsic framework flexibility into porous aromatic frameworks (PAFs). Through Yamamoto-type copolymerization of a rigid tetrahedral monomer (tetrakis(4-bromophenyl)methane) and a flexible counterpart (tetrakis[(4-bromophenoxy)methyl]methane), we synthesized a series of flexible PAFs (FPAF-x, x = 0-2) with tunable flexibility. FPAF-0.5 with moderate flexibility and surface area (854 m2 g-1) achieves exceptionally high volatile organic compound (VOC) adsorption capacities for various VOCs (e.g., 410.7 wt% for THF and 339.4 wt% for 3-methylthiophene), outperforming many other porous materials reported to date. Both thermodynamic equilibrium and dynamics VOC vapor adsorption studies reveal that optimal flexibility enables guest-adaptive structural transformation, allowing pore expansion to accommodate additional VOC molecules after initial pore filling. Moreover, polar and aromatic VOCs induce greater framework expansion than nonpolar analogues, which can also enhance the VOC uptake capacity in FPAFs. This work establishes flexibility engineering as a design principle for next-generation adsorbents, improving the efficiency of VOC adsorption.

Hexagonal boron nitride (h-BN) is a two-dimensional (2D) layered material with a structure similar to graphite and it has potential as a hydrogen and ammonia storage material. However, dense packing in the standard h-BN structure limits its surface area and prevents the B and N from being adsorption sites. In this study, the addition of Mg2+ during h-BN synthesis facilitated the growth of lattice dislocations and led to a cross-linked three-dimensional (3D) porous structure. A proposed formation mechanism for porous h-BN was confirmed by several characterization routes, most clearly by high-resolution transmission electron microscopy (HRTEM). Porous Mg/BNs exhibited high H2 and NH3 uptakes and showed potential for H2 and NH3 storage.

Radiation-resistant nanoporous adsorbent that can realize absolute CO2/Xe (Kr) separation without Xe and Kr loss is crucial, but yet to be achieved for accurate and reliable nuclear fuel burnup analysis. Herein, two hybrid ultramicroporous materials (NbOFFIVE-1-Ni and TIFSIX-3-Co) are presented for highly efficient CO2/Xe and CO2/Kr separation in the nuclear reprocessing off-gas. Nearly complete CO2/Xe (Kr) molecular sieving separations are achieved in NbOFFIVE-1-Ni with CO2/Xe and CO2/Kr selectivities both exceeding 11 000 before and after 50 kGy irradiation. Total photon cross sections of different elements, coordination number, and crystal orbital overlap population calculation that combines atoms, chemical bonds, and crystal structure are used to analyze the radiation stability of the hybrid ultramicroporous materials. Furthermore, the dynamic breakthrough and desorption measurement confirmed the ultra-low Xe (Kr) loss ratio (0.24% for Xe and 0.3% for Kr) of NbOFFIVE-1-Ni adsorbent under simulated reprocessing off-gas separation. This work not only provides a benchmark CO2/Xe (Kr) adsorbent for reliable nuclear fuel burnup analysis but also proposes a new perspective to understand the radiation stability of hybrid ultramicroporous materials.

The aluminum electrolysis industry generates massive greenhouse gas emissions dominated by CO2 and perfluorocarbons (PFCs, CF4/C2F6), presenting dual challenges of climate impact and resource waste. Here, we report a robust nickel-based metal-organic framework (SIFSIX-3-Ni) featuring confined square channels (3.55 Å) that achieves the molecular-sieving separation of CO2 from CF4/C2F6 mixtures. Unlike conventional adsorbents, this MOF exhibits exceptional CO2 selectivity (>105 IAST) through precise size exclusion and strong quadrupole interactions with CO2 by proximal fluorine arrays. Breakthrough experiments validate its molecular-sieving capability across varying gas compositions (CO2: 50-80 vol %), with 40-65 min g-1 CO2 retention times enabling direct CF4/C2F6 enrichment. The enriched CF4/C2F6 was subjected to an aspen distillation simulation to obtain 99.99% CF4 and C2F6. Crucially, the synthetic MOF demonstrates remarkable stability under corrosive HF exposure and maintains a 100% CO2 adsorption capacity over five temperature-swing cycles. This work establishes a paradigm for simultaneous carbon capture and high-value PFC recovery in advancing sustainable aluminum electrolysis off-gas utilization.

Capture and purification of CO2, Xe, and Kr from used nuclear fuel (UNF) reprocessing off-gas is of environmental and industrial importance. However, designing adsorbents that simultaneously exhibit high capacity, selectivity, and radiation resistance remains a significant challenge. Herein, three MOFs (HUKST-1, CALF-20, and SIFISIX-3-Ni) possessing distinct pore environments for CO2/Xe/Kr adsorption separation from UNF reprocessing off-gas are evaluated. CALF-20 demonstrates exceptional performance due to its pore environment, which facilitates differential recognition and polarization of the target gases-a key factor in achieving selective gas preparative chromatography separation. Adsorption isotherms, breakthrough curves, and chromatographic profiles reveal that CALF-20 offers an excellent capture and separation performance for CO2, Xe, and Kr under dilute conditions. Furthermore, gamma-ray irradiation experiments confirme the high radiation stability of CALF-20, indicating its strong potential for practical application. This work establishes CALF-20 as a benchmark adsorbent for one-step CO2/Xe/Kr purification from UNF reprocessing off-gas and highlights the promise of rational pore environment control in MOFs to engineer tailored adsorbents for specialized separations.

The development of efficient adsorbents for perfluorinated electronic specialty gases' (F-gases) recovery presents significant challenges in the chip plasma etching process. In this study, we focus on preparing Ti- and W-replaced MFI zeolites, which offer abundant Lewis acid sites, to enhance the separation of F-gases toward N2. Through single-component gas adsorption and ideal adsorbed solution theory selectivity analyses, the Ti- and W-doped MFI zeolites demonstrate remarkable separation performance. Additionally, dynamic breakthrough experiments have confirmed the effective capture of F-gases using Ti- and W-doped MFI zeolites. The intrinsic adsorption mechanism was also investigated by the Grand Canonical Monte Carlo and independent gradient model (IGM) simulations. IGM results indicate that there is a strong charge transfer interaction between the polar Lewis acid sites in the MFI channel and F-gases with high polarizability. These results highlight the promising potential of MFI zeolites with abundant Lewis acid sites for addressing F-gas capture in the semiconductor industries.

The development of high-performance adsorbents is essential for the efficient capture and recycling of perfluorinated electronic specialty gases (F-gases) from semiconductor industrial exhaust gas. Herein, a robust porphyrin-based MOF (Al-PMOF) with ultra-micropores and high stability was synthesized, and its adsorption and separation performance toward F-gases was also intensely investigated. The results demonstrate that the polar sites of aluminum-oxygen (Al-O) clusters on the pore surfaces of Al-PMOF enhance adsorption selectivity toward F-gases (CF4, NF3, and SF6) via strong induced polarization interactions. The adsorption capacities of AlPMOF for CF4, NF3, and SF6 reached 2.23, 3.00, and 6.15 mmol/g, respectively, at 298 K and 1.0 bar, surpassing many previously reported benchmark porous materials. Selectivity calculations based on the Ideal Adsorbed Solution Theory (IAST) reveal that Al-PMOF exhibits exceptional adsorption selectivity for F-gases. For instance, the selectivity of Al-PMOF for SF6 in a binary mixture (SF6:N2 = 1:9, v/v) is as high as 581. Fixed-bed breakthrough experiments further validated the superior outstanding dynamic adsorption selectivity of Al-PMOF for Fgases under simulated operating conditions. The intrinsic adsorption mechanism of Al-PMOF for F-gases was elucidated through molecular-level simulations based on Density Functional Theory (DFT). These results underscore the significant potential of Al-PMOF with induced polarization effect for addressing the critical challenges of high-value-added F-gases separation and recovery in semiconductor manufacturing processes.

Porous organic frameworks (POFs) represent a new family of porous materials distinguished by high chemical stability, thermal stability, structural tunabiltity, chemical functionality, and high porosity. In this study, we synthesized a F-containing POF, termed PAF-109 (PAF = porous aromatic framework), through the Schiff base reaction of 1,3,5-triformylphloroglucinol and 4,4 '-Diaminoctafluorobiphenyl, with p-toluenesulfonic acid serving as the catalyst. Nitrogen sorption analysis revealed that PAF-109 shows a Brunauer - Emmet - Teller surface area of 718 m2/g, nearly four times greater than that of previously reported TpBD-F8. Interestingly, PAF-109 exhibits a low CH4 uptake of only 0.18mmol/g at 298 K and 1 bar. Despite this, PAF-109 shows high selectivity for the separation of C 3H8 over CH4.

Abstract Porous aromatic framework 1 (PAF‐1) is an extremely representative nanoporous organic framework owing to its high stability and exceptionally high surface area. Currently, the synthesis of PAF‐1 is catalyzed by the Ni(COD)2/COD/bpy system, suffering from great instability and high cost. Herein, we developed an in situ reduction of the Ni(II) catalytic system to synthesize PAF‐1 in low cost and high yield. The active Ni(0) species produced from the NiCl2/bpy/NaI/Mg catalyst system can effectively catalyze homocoupling of tetrakis(4‐bromophenyl)methane at the room temperature to form PAF‐1 with high Brunauer–Emmett–Teller (BET)‐specific surface area up to 4948 m2 g−1 (Langmuir surface area, 6785 m2 g−1). The possible halogen exchange and dehalogenation coupling mechanisms for this new catalytic process in PAF's synthesis are discussed in detail. The efficiency and universality of this innovative catalyst system have also been demonstrated in other PAFs' synthesis. This work provides a cheap, facile, and efficient method for scalable synthesis of PAFs and explores their application for high‐pressure storage of Xe and Kr.