Optimal Pore Chemistry in an Ultramicroporous Metal-Organic Framework for Benchmark Inverse CO2 /C2 H2 Separation

Increased CO2/N2 selectivity by stepwise fluorination in isoreticular ultramicroporous metal-organic frameworks

Exploration of porous adsorbents with high CO2/N2 selectivity is of great significance for reducing CO2 content in the atmosphere. In this study, a series of isoreticular ultramicroporous fluorinated metal-organic frameworks (MOFs) were prepared to explore the benefits of fluorinated ultramicropores in improving CO2/N2 selectivity. Gas adsorption measurements revealed that the increase in the number of fluorine atoms in a ligand molecule leads to the increased CO2 uptakes and CO2/N2 selectivity. Theoretical calculations indicate that the interaction between the fluorine atoms and adsorbed CO2 molecules enhances the CO2-philicity, offering useful insight into the improvement of CO2/N2 selectivity in isoreticular frameworks.

Precise Modulation of CO2 Sorption in Ti8Ce2-Oxo Clusters: Elucidating Lewis Acidity of the Ce Metal Sites and Structural Flexibility

Investigating the structure-property correlation in porous materials is a fundamental and consistent focus in various scientific domains, especially within sorption research. Metal oxide clusters with capping ligands, characterized by intrinsic cavities formed through specific solid-state packing, demonstrate significant potential as versatile platforms for sorption investigations due to their precisely tunable atomic structures and inherent long-range order. This study presents a series of Ti8Ce2-oxo clusters with subtle variations in coordinated linkers and explores their sorption behavior. Notably, Ti8Ce2-BA (BA denotes benzoic acid) manifests a distinctive two-step profile during the CO2 adsorption, accompanied by a hysteresis loop. This observation marks a new instance within the metal oxide cluster field. Of intrigue, the presence of unsaturated Ce(IV) sites was found to be correlated with the stepped sorption property. Moreover, the introduction of an electrophilic fluorine atom, positioned ortho or para to the benzoic acid, facilitated precise control over gate pressure and stepped sorption quantities. Advanced in situ techniques systematically unraveled the underlying mechanism behind this unique sorption behavior. The findings elucidate that robust Lewis base-acid interactions are established between the CO2 molecules and Ce ions, consequently altering the conformation of coordinated linkers. Conversely, the F atoms primarily contribute to gate pressure variation by influencing the Lewis acidity of the Ce sites. This research advances the understanding in fabricating metal-oxo clusters with structural flexibility and provides profound insights into their host-guest interaction motifs. These insights hold substantial promise across diverse fields and offer valuable guidance for future adsorbent designs grounded in fundamental theories of structure-property relationships.

Mechanistical Insights into the Ultrasensitive Detection of Radioactive and Chemotoxic UO22+ Ions by a Porous Anionic Co-Metal-Organic Framework

Development of a simple, cost-efficient, and portable UO22+ sensory probe with high selectivity and sensitivity is highly desirable in the context of monitoring radioactive contaminants. Herein, we report a luminescent Co-based metal-organic framework (MOF), {[Me2NH2]0.5[Co(DATRz)0.5(NH2BDC)]·xG}n (1), equipped with abundant amino functionalities for the selective detection of uranyl cations. The ionic structure consists of two types of channels decorated with plentiful Lewis basic amino moieties, which trigger a stronger acid-base interaction with the diffused cationic units and thus can selectively quench the fluorescence intensity in the presence of other interfering ions. Furthermore, the limit of detection for selective UO22+ sensing was achieved to be as low as 0.13 μM (30.94 ppb) with rapid responsiveness and multiple recyclabilities, demonstrating its excellent efficacy. Density functional theory (DFT) calculations further unraveled the preferred binding sites of the UO22+ ions in the tubular channel of the MOF structure. Orbital hybridization between NH2BDC/DATRz and UO22+ together with its significantly large electron-accepting ability is identified as responsible for the luminescence quenching. More importantly, the prepared 1@PVDF {poly(vinylidene difluoride)} mixed-matrix membrane (MMM) displayed good fluorescence activity comparable to 1, which is of great significance for their practical employment as MOF-based luminosensors in real-world sensing application.

CO2-Based Stable Porous Metal-Organic Frameworks for CO2 Utilization

The transformation of carbon dioxide (CO2) into functional materials has garnered considerable worldwide interest. Metal-organic frameworks (MOFs), as a distinctive class of materials, have made great contributions to CO2 capture and conversion. However, facile conversion of CO2 to stable porous MOFs for CO2 utilization remains unexplored. Herein, we present a facile methodology of using CO2 to synthesize stable zirconium-based MOFs. Two zirconium-based MOFs CO2-Zr-DEP and CO2-Zr-DEDP with face-centered cubic topology were obtained via a sequential desilylation-carboxylation-coordination reaction. The MOFs exhibit excellent crystallinity, as verified through powder X-ray diffraction and high-resolution transmission electron microscopy analyses. They also have notable porosity with high surface area (SBET up to 3688 m2 g-1) and good CO2 adsorption capacity (up to 12.5 wt %). The resulting MOFs have abundant alkyne functional moieties, confirmed through 13C cross-polarization/magic angle spinning nuclear magnetic resonance and Fourier transform infrared spectra. Leveraging the catalytic prowess of Ag(I) in diverse CO2-involved reactions, we incorporated Ag(I) into zirconium-based MOFs, capitalizing on their interactions with carbon-carbon π-bonds of alkynes, thereby forming a heterogeneous catalyst. This catalyst demonstrates outstanding efficiency in catalyzing the conversion of CO2 and propargylic alcohols into cyclic carbonates, achieving >99% yield at room temperature and atmospheric pressure conditions. Thus, this work provides a dual CO2 utilization strategy, encompassing the synthesis of CO2-based MOFs (20-24 wt % from CO2) and their subsequent application in CO2 capture and conversion processes. This approach significantly enhances overall CO2 utilization.

Reverse Separation of Carbon Dioxide and Acetylene in Two Isostructural Copper Pyridine-Carboxylate Frameworks

Separating acetylene from carbon dioxide is important but highly challenging due to their similar molecular shapes and physical properties. Adsorptive separation of carbon dioxide from acetylene can directly produce pure acetylene but is hardly realized because of relatively polarizable acetylene binds more strongly. Here, we reverse the CO2 and C2H2 separation by adjusting the pore structures in two isoreticular ultramicroporous metal-organic frameworks (MOFs). Under ambient conditions, copper isonicotinate (Cu(ina)2), with relatively large pore channels shows C2H2-selective adsorption with a C2H2/CO2 selectivity of 3.4, whereas its smaller-pore analogue, copper quinoline-5-carboxylate (Cu(Qc)2) shows an inverse CO2/C2H2 selectivity of 5.6. Cu(Qc)2 shows compact pore space that well matches the optimal orientation of CO2 but is not compatible for C2H2. Neutron powder diffraction experiments confirmed that CO2 molecules adopt preferential orientation along the pore channels during adsorption binding, whereas C2H2 molecules bind in an opposite fashion with distorted configurations due to their opposite quadrupole moments. Dynamic breakthrough experiments have validated the separation performance of Cu(Qc)2 for CO2/C2H2 separation.

Host-Host Interactions Enhanced the Structural Rigidity in a 6-Fold Interpenetrated Diamondoid Metal-Organic Framework Exhibiting C2H2/C2H4 Separation

Multi-interpenetrated metal-organic frameworks (MOFs) have exhibited excellent performance in selective adsorption due to the variable post-interspersed flexibility, but the design and control remain challenging. Herein, two anthracene-based ligands, 4,4'-(anthracene-9,10-diyl)dibenzoic acid (H2L1) and 9,10-di(pyridin-4-yl)anthracene (L2), are used to construct a new three-dimensional 6-fold interpenetrated MOF [Zn(L1)(L2)]n (NBU-X1), which exhibits multiple C-H···π interactions that enhance the structural rigidity, thereby entangling with a C2H2/C2H4 separation performance. In this material, the incorporation of abundant anthracene rings within the framework not only partitions and restricts the pore window size to a quasi-double pore but also stabilizes it through host-host interactions. The structural stability upon heating or guest displacement/removal has been investigated by single-crystal X-ray diffraction and in situ variable-temperature powder X-ray diffraction, in contrast to the extreme flexibility of most multi-interpenetrated MOFs. The performance of purifying C2H4 from C2H2/C2H4 mixtures has been proved by dynamic breakthrough tests.

Isoreticular Contraction of Cage-like Metal-Organic Frameworks with Optimized Pore Space for Enhanced C2H2/CO2 and C2H2/C2H4 Separations

The C2H2 separation from CO2 and C2H4 is of great importance yet highly challenging in the petrochemical industry, owing to their similar physical and chemical properties. Herein, the pore nanospace engineering of cage-like mixed-ligand MFOF-1 has been accomplished via contracting the size of the pyridine- and carboxylic acid-functionalized linkers and introducing a fluoride- and sulfate-bridging cobalt cluster, based on a reticular chemistry strategy. Compared with the prototypical MFOF-1, the constructed FJUT-1 with the same topology presents significantly improved C2H2 adsorption capacity, and selective C2H2 separation performance due to the reduced cage cavity size, functionalized pore surface, and appropriate pore volume. The introduction of fluoride- and sulfate-bridging cubane-type tetranuclear cobalt clusters bestows FJUT-1 with exceptional chemical stability under harsh conditions while providing multiple potential C2H2 binding sites, thus rendering the adequate ability for practical C2H2 separation application as confirmed by the dynamic breakthrough experiments under dry and humid conditions. Additionally, the distinct binding mechanism is suggested by theoretical calculations in which the multiple supramolecular interactions involving C-H···O, C-H···F, and other van der Waals forces play a critical role in the selective C2H2 separation.

Separation of High-Purity C2H2 from Binary C2H2/CO2 Using Robust Al-Based MOFs Comprising Nitrogen-Containing Heterocyclic Dicarboxylate

In this study, three nitrogen-containing aluminum-based metal-organic frameworks (Al-MOFs), namely, CAU-10pydc, MOF-303, and KMF-1, were investigated for the efficient separation of a C2H2/CO2 gas mixture. Among these three Al-MOFs, KMF-1 demonstrated the highest selectivity for C2H2/CO2 separation (6.31), primarily owing to its superior C2H2 uptake (7.90 mmol g-1) and lower CO2 uptake (2.82 mmol g-1) compared to that of the other two Al-MOFs. Dynamic breakthrough experiments, using an equimolar binary C2H2/CO2 gas mixture, demonstrated that KMF-1 achieved the highest separation performance. It yielded 3.42 mmol g-1 of high-purity C2H2 (>99.95%) through a straightforward desorption process under He purging at 298 K and 1 bar. To gain insights into the distinctive characteristics of the pore surfaces of structurally similar CAU-10pydc and KMF-1, we conducted computational simulations using canonical Monte Carlo and dispersion-corrected density functional theory methods. These simulations revealed that the secondary amine (C2N-H) groups in KMF-1 played a more significant role in differentiating between C2H2 and CO2 compared to that of the N atoms in CAU-10pydc and MOF-303. Consequently, KMF-1 emerged as a promising adsorbent for the separation of high-purity C2H2 from binary C2H2/CO2 gas mixtures.

Solvent-Directed Construction of a Nanoporous Metal-Organic Framework with Potential in Selective Adsorption and Separation of Gas Mixtures Studied by Grand Canonical Monte Carlo Simulations

In this report, a microporous metal-organic framework of [Ca(TDC)(DMA)]n (1) and a two-dimensional coordination polymer of [Ca(TDC)(DMF)2 ]n (2), (TDC2- =Thiophene-2,5-dicarboxylate, DMA=N, N'-dimethylacetamide and DMF=N, N'-dimethylformamide) based on Ca(II) were designed by the effect of solvent, and X-ray analysis was performed for the single crystals of 1 and 2. Then, compound 1 was synthesized in three different methods and identified with a set of analyses. Compared to other adsorbents, MOFs are widely used in the field of adsorption and separation of various gases due to a series of distinctive features such as diverse and adjustable structures pores with different dimensions, high porosity and surface area with regular distribution of active sites. Therefore, the ability of 1 to uptake single gases (CH4 , CO2 , C2 H2 , H2, and N2 ) and separation of several binary mixtures of gases (CO2 /CH4 , CO2 /N2 , CO2 /H2 and CO2 /C2 H2 ), were investigated using Grand Canonical Monte Carlo simulations. Volumetric and gravimetric adsorption isotherms in various operating conditions, the isosteric heat of adsorption (qst ), the chemical potential for each thermodynamic state, and snapshots during the simulation process were reported in all cases. The results obtained from the adsorption simulation indicate that compound 1 has a high capacity for uptake of H2 (16 mmol g-1 ) and N2 (12.5 mmol g-1 ), CO2 (6.6 mmol g-1 ), C2 H2 (5 mmol g-1 ) and CH4 (1.5 mmol g-1 ) gases at 1 bar. It also performs well in separating CO2 in binary mixtures, which can be attributed to the presence of open metal sites in nodes of 1 and their electrostatic tendency to interact with CO2 containing the higher quadrupole dipole moment compared to other components of the mixture.

Precise Preparation of Triarylboron-Based Graphdiyne Analogues for Gas Separation

A series of triarylboron-based graphdiyne analogues (TAB-GDYs) with tunable pore size were prepared through copper mediated coupling reaction. The elemental composition, chemical bond, morphology of TAB-GDYs were well characterized. The crystallinity was confirmed by selected area electron diffraction (SAED) and stacking modes were studied in combination with high resolution transmission electron microscope (HRTEM) and structure simulation. The absorption and desorption isotherm revealed relatively high specific surface area of these TAB-GDYs up to 788 m2  g-1 for TMTAB-GDY, which decreased as pore size enlarged. TAB-GDYs exhibit certain selectivity for CO2 /N2 (21.9), CO2 /CH4 (5.3), CO2 /H2 (41.8) and C2 H2 /CO2 (2.3). This work has developed a series of boron containing two-dimensional frameworks with clear structures and good stability, and their tunable pore sizes have laid the foundation for future applications in the gas separation field.

Optimizing Sieving Effect for CO2 Capture from Humid Air Using an Adaptive Ultramicroporous Framework

Excessive CO2 in the air can not only lead to serious climate problems but also cause serious damage to humans in confined spaces. Here, a novel metal-organic framework (FJI-H38) with adaptive ultramicropores and multiple active sites is prepared. It can sieve CO2 from air with the very high adsorption capacity/selectivity but the lowest adsorption enthalpy among the reported physical adsorbents. Such excellent adsorption performances can be retained even at high humidity. Mechanistic studies show that the polar ultramicropore is very suitable for molecular sieving of CO2 from N2 , and the distinguishable adsorption sites for H2 O and CO2 enable them to be co-adsorbed. Notably, the adsorbed-CO2 -driven pore shrinkage can further promote CO2 capture while the adsorbed-H2 O-induced phase transitions in turn inhibit H2 O adsorption. Moreover, FJI-H38 has excellent stability and recyclability and can be synthesized on a large scale, making it a practical trace CO2 adsorbent. This will provide a new strategy for developing practical adsorbents for CO2 capture from the air.

Recent advances in the chemistry and applications of fluorinated metal-organic frameworks (F-MOFs)

Metal-organic frameworks are a class of porous crystalline materials based on the ordered connection of metal centers or metal clusters by organic linkers with comprehensive functionalities. The interest in these materials is rapidly moving towards their application in industry and real life. In this context, cheap and sustainable synthetic strategies of MOFs with tailored structures and functions are nowadays a topic widely studied from different points of view. In this review, fluorinated MOFs (F-MOFs) and their applications are investigated. The principal aim is to provide an overview of the structural features and the main application of MOFs containing fluorine atoms both as anionic units or as coordinating elements of more complex inorganic units and, therefore, directly linked to the structural metals or as part of fluorinated linkers used in the synthesis of MOFs. Herein we present a review of F-MOFs reported in the recent literature compared to benchmark compounds published over the last 10 years. The compounds are discussed in terms of their structure and properties according to the aforementioned classification, with an insight into the different chemical nature of the bonds. The application fields of F-MOFs, especially in sustainability related issues, such as harmful gas sorption and separation, will also be discussed. F-MOFs are compounds containing fluorine atoms in their framework and they can be based on: (a) fluorinated metallic or semi-metallic anionic clusters or: (b) fluorinated organic linkers or (c) eventually containing both the building blocks. The nature of a covalent C-F bond in terms of length, charge separation and dipole moment sensibly differs from that of a partly ionic M-F (M = metal) one so that the two classes of materials (points a and b) have different properties and they find various application fields. The study shows how the insertion of polar M-F and C-F bonds in the MOF structure may confer several advantages in terms of interaction with gaseous molecules and the compounds can find application in gas sorption and separation. In addition, hydrophobicity tends to increase compared to non-fluorinated analogues, resulting in an overall improvement in moisture stability.

One-step ethylene purification from ternary mixtures by an ultramicroporous material with synergistic binding centers

Developing advanced porous materials with industrial potential to separate multicomponent gas mixtures that are structurally similar is a crucial but challenging task. Here, we report the efficient one-step separation of ethylene (C2H4) from acetylene (C2H2) and carbon dioxide (CO2) using an ultramicroporous metal-organic framework UTSA-16. The synergistic effect of the polarized carboxyl groups and coordinated water molecules in its pore channel enables the material to have high uptakes for C2H2 and CO2 due to electrostatic potential matching, as well as excellent separation selectivity against C2H4. Breakthrough experiments suggest that UTSA-16 can efficiently separate 99.9% pure C2H4 from ternary mixtures with a high productivity of 403 L kg-1. Moreover, the preparation cost of UTSA-16 is significantly lower than other related adsorbents by 40-2000 times, indicating its unique potential for industrial applications.

A Microporous Hydrogen Bonded Organic Framework for Highly Selective Separation of Carbon Dioxide over Acetylene

The separation of acetylene (C2 H2 ) from carbon dioxide (CO2 ) is a very important but challenging task due to their similar molecular dimensions and physical properties. In terms of porous adsorbents for this separation, the CO2 -selective porous materials are superior to the C2 H2 -selective ones because of the cost- and energy-efficiency but have been rarely achieved. Herein we report our unexpected discovery of the first hydrogen bonded organic framework (HOF) constructed from a simple organic linker 2,4,6-tri(1H-pyrazol-4-yl)pyridine (PYTPZ) (termed as HOF-FJU-88) as the highly CO2 -selective porous material. HOF-FJU-88 is a two-dimensional HOFs with a pore pocket of about 7.6 Å. The activated HOF-FJU-88 takes up a high amount of CO2 (59.6 cm3  g-1 ) at ambient conditions with the record IAST selectivity of 1894. Its high performance for the CO2 /C2 H2 separation has been further confirmed through breakthrough experiments, in situ diffuse reflectance infrared spectroscopy and molecular simulations.

Topological Design of Unprecedented Metal-Organic Frameworks Featuring Multiple Anion Functionalities and Hierarchical Porosity for Benchmark Acetylene Separation

Separation of acetylene (C2 H2 ) from carbon dioxide (CO2 ) or ethylene (C2 H4 ) is industrially important but still challenging so far. Herein, we developed two novel robust metal organic frameworks AlFSIX-Cu-TPBDA (ZNU-8) with znv topology and SIFSIX-Cu-TPBDA (ZNU-9) with wly topology for efficient capture of C2 H2 from CO2 and C2 H4 . Both ZNU-8 and ZNU-9 feature multiple anion functionalities and hierarchical porosity. Notably, ZNU-9 with more anionic binding sites and three distinct cages displays both an extremely large C2 H2 capacity (7.94 mmol/g) and a high C2 H2 /CO2 (10.3) or C2 H2 /C2 H4 (11.6) selectivity. The calculated capacity of C2 H2 per anion (4.94 mol/mol at 1 bar) is the highest among all the anion pillared metal organic frameworks. Theoretical calculation indicated that the strong cooperative hydrogen bonds exist between acetylene and the pillared SiF6 2- anions in the confined cavity, which is further confirmed by in situ IR spectra. The practical separation performance was explicitly demonstrated by dynamic breakthrough experiments with equimolar C2 H2 /CO2 mixtures and 1/99 C2 H2 /C2 H4 mixtures under various conditions with excellent recyclability and benchmark productivity of pure C2 H2 (5.13 mmol/g) or C2 H4 (48.57 mmol/g).

Discriminatory Gate-Opening Effect in a Flexible Metal-Organic Framework for Inverse CO2 /C2 H2 Separation

Considering the significant application of acetylene (C2 H2 ) in the manufacturing and petrochemical industries, the selective capture of impurity carbon dioxide (CO2 ) is a crucial task and an enduring challenge. Here, a flexible metal-organic framework (Zn-DPNA) accompanied by a conformation change of the Me2 NH2 + ions in the framework is reported. The solvate-free framework provides a stepped adsorption isotherm and large hysteresis for C2 H2 , but type-I adsorption for CO2 . Owing to their uptakes difference before gate-opening pressure, Zn-DPNA demonstrated favorable inverse CO2 /C2 H2 separation. According to molecular simulation, the higher adsorption enthalpy of CO2 (43.1 kJ mol-1 ) is due to strong electrostatic interactions with Me2 NH2 + ions, which lock the hydrogen-bond network and narrow pores. Furthermore, the density contours and electrostatic potential verifies the middle of the cage in the large pore favors C2 H2 and repels CO2 , leading to the expansion of the narrow pore and further diffusion of C2 H2 . These results provide a new strategy that optimizes the desired dynamic behavior for one-step purification of C2 H2 .

pH-Stable Zn(II) Coordination Polymer as a Multiresponsive Turn-On and Turn-Off Fluorescent Sensor for Aqueous Medium Detection of Al(III) and Cr(VI) Oxo-Anions

Nowadays, coordination polymers (CPs) are promising candidates as sensory materials for their high sensitivity, improved selectivity, fast responsive nature, as well as good recyclability. However, poor chemical stability often makes their practical usage limited. Herein, employing a mixed ligand approach, we constructed a chemically robust CP, {[Zn2L2(DPA)2]·3H2O}n (IITKGP-70, IITKGP stands for the Indian Institute of Technology Kharagpur), which exhibited excellent framework robustness not only in water but also over a broad range of pH solutions (pH = 3-11). The developed framework displayed high selectivity and sensitivity for the detection of trivalent Al3+ ions and toxic hexavalent Cr(VI)-oxo anions in an aqueous medium. The developed framework exhibited an aqueous medium Al3+ turn-on phenomenon with a limit of detection (LOD) value of 1.29 μM, whereas a turn-off effect was observed for toxic oxo-anions (Cr2O72- and CrO42-) having LOD values of 0.27 and 0.71 μM, respectively. Both turn-on and turn-off mechanisms are speculated via spectroscopic methods coupled with several ex situ studies. Such a multiresponsive nature (both turn-on and turn-off) for aqueous medium detection of targeted cations and anions simultaneously in a single platform coupled with high robustness, ease of scalability, recyclability, and fast-responsive nature makes IITKGP-70 highly fascinating as a sensory material for real-world applications.

Multifunctional Roles of Dihydrotetrazine-Decorated Zr-MOFs in Photoluminescence and Colorimetrism for Discrimination of Arsenate and Phosphate Ions in Water

The high chemical and structural stabilities of zirconium (Zr)-based metal-organic frameworks (MOFs) in aquatic media make them ideal candidates for wastewater treatment. Rational decoration or Zr-MOFs with functional groups can significantly extend their application in this area. In this work, two well-known Zr-MOFs, UiO-66 and MIL-140-A, were functionalized with dihydrotetrazine function to increase their capability in water treatment. Investigations reveal that these two dihydrotetrazine (DHTZ)-functionalized MOFs, namely UiO-66(Zr)-DHTZ and MIL-140(Zr)-DHTZ, can be applied as a two-component array for highly selective and sensitive discrimination of arsenate (AsO43-) and phosphate (PO43-) ions in water in the presence of other anions. Photoluminescence (PL) tests using UiO-66(Zr)-DHTZ show that this MOF can detect these two anions via a ratiometric response, 1.74 for arsenate and 1.84 for phosphate at 2 μM, with superior detection limits (7.2 × 10-8 M for AsO43- and 4.3 × 10-8 M for PO43-). The ratiometric PL response of UiO-66(Zr)-DHTZ toward arsenate and phosphate anions arises possibly from the arsenate-dihydrotetrazine hydrogen bonding. In the next step, colorimetric tests using MIL-140(Zr)-DHTZ were conducted to discriminate the arsenate from phosphate with a very low detection limit at nanomolar level. This MOF undergoes a yellow-to-pink color change in the presence of arsenate ions, while no color change is observed in the presence of phosphate. This color change is observed through conversion of dihydrotetrazine sites inside the pores of MIL-140(Zr)-DHTZ into tetrazine. Altogether, the PL response of UiO-66(Zr)-DHTZ is originated from the hydrogen bond-donating/accepting character of DHTZ function, while the colorimetric response of MIL-140(Zr)-DHTZ is based on the chemical conversion of DHTZ function. This work clearly shows that the decoration of Zr-based MOFs with multicharacter functional groups can develop their application in wastewater treatment as multipurpose platforms.

Temperature-dependent rearrangement of gas molecules in ultramicroporous materials for tunable adsorption of CO2 and C2H2

The interactions between adsorbed gas molecules within porous metal-organic frameworks are crucial to gas selectivity but remain poorly explored. Here, we report the modulation of packing geometries of CO₂ and C₂H₂ clusters within the ultramicroporous CUK-1 material as a function of temperature. In-situ synchrotron X-ray diffraction reveals a unique temperature-dependent reversal of CO₂ and C₂H₂ adsorption affinities on CUK-1, which is validated by gas sorption and dynamic breakthrough experiments, affording high-purity C₂H₂ (99.95%) from the equimolar mixture of C₂H₂/CO₂ via a one-step purification process. At low temperatures (<253 K), CUK-1 preferentially adsorbs CO₂ with both high selectivity (>10) and capacity (170 cm³ g^-1) owing to the formation of CO₂ tetramers that simultaneously maximize the guest-guest and host-guest interactions. At room temperature, conventionally selective adsorption of C₂H₂ is observed. The selectivity reversal, structural robustness, and facile regeneration of CUK-1 suggest its potential for producing high-purity C₂H₂ by temperature-swing sorption.

Highly Efficient CO2/C2H2 Separation by Porous Graphene via Quadrupole Gating Mechanism

Acetylene (C₂H₂) is an important and widely used raw material in various industries (such as petrochemical). Generally, a product yield is proportional to the purity of C₂H₂; however, C₂H₂ from a typical industrial gas-production process is commonly contaminated by CO₂. So far, the achievement of high-purity C₂H₂ separated from a CO₂/C₂H₂ mixture is still challenging due to their very close molecular dimensions and boiling temperatures. Taking advantage of their quadrupoles with opposite signs, here, we show that the graphene membrane embedded with crown ether nanopores can achieve an unprecedented separation efficiency of CO₂/C₂H₂. Combining the molecular dynamics simulation and the density functional theory (DFT) approaches, we discovered that the electrostatic gas-pore interaction favorably allows the fast transport of CO₂ through crown ether nanopores while completely prohibiting C₂H₂ transport, which yields a remarkable permeation selectivity. In particular, the utilized crown ether pore is capable of allowing the individual transport of CO₂ while completely rejecting the passage of C₂H₂, independent of the applied pressures, fed gases ratios, and exerted temperatures, featuring the superiority and robustness of the crown pore in CO₂/C₂H₂ separation. Further, DFT and PMF calculations demonstrate that the transport of CO₂ through the crown pore is energetically more favorable than the transport of C₂H₂. Our findings reveal the potential application of graphene crown pore for CO₂ separation with outstanding performance.

Immobilization of the Polar Group into an Ultramicroporous Metal-Organic Framework Enabling Benchmark Inverse Selective CO2/C2H2 Separation with Record C2H2 Production

One-step harvest of high-purity light hydrocarbons without the desorption process represents an advanced and highly efficient strategy for the purification of target substances. The separation and purification of acetylene (C₂H₂) from carbon dioxide (CO₂) by CO₂-selective adsorbents are urgently demanded yet are very challenging owing to their similar physicochemical properties. Here, we employ the pore chemistry strategy to adjust the pore environment by immobilizing polar groups into an ultramicroporous metal-organic framework (MOF), achieving one-step manufacture of high-purity C₂H₂ from CO₂/C₂H₂ mixtures. Embedding methyl groups into prototype stable MOF (Zn-ox-trz) not only changes the pore environment but also improves the discrimination of guest molecules. The methyl-functionalized Zn-ox-mtz thus exhibits the benchmark reverse CO₂/C₂H₂ uptake ratio of 12.6 (123.32/9.79 cm³ cm^-3) and an exceptionally high equimolar CO₂/C₂H₂ selectivity of 1064.9 at ambient conditions. Molecular simulations reveal that the synergetic effect of pore confinement and surfaces decorated with methyl groups provides high recognition of CO₂ molecules through multiple van der Waals interactions. The column breakthrough experiments suggest that Zn-ox-mtz dramatically achieved the one-step purification capacity of C₂H₂ from the CO₂/C₂H₂ mixture with a record C₂H₂ productivity of 2091 mmol kg^-1, surpassing all of the CO₂-selective adsorbents reported so far. In addition, Zn-ox-mtz exhibits excellent chemical stability under different pH values of aqueous solutions (pH = 1-12). Moreover, the highly stable framework and excellent inverse selective CO₂/C₂H₂ separation performance showcase its promising application as a C₂H₂ splitter for industrial manufacture. This work paves the way to developing reverse-selective adsorbents for the challenging gas separation process.

Exclusive Recognition of CO2 from Hydrocarbons by Aluminum Formate with Hydrogen-Confined Pore Cavities

Exclusive capture of carbon dioxide (CO₂) from hydrocarbons via adsorptive separation is an important technology in the petrochemical industry, especially for acetylene (C₂H₂) production. However, the physicochemical similarities between CO₂ and C₂H₂ hamper the development of CO₂-preferential sorbents, and CO₂ is mainly discerned via C recognition with low efficiency. Here, we report that the ultramicroporous material Al(HCOO)₃, ALF, can exclusively capture CO₂ from hydrocarbon mixtures, including those containing C₂H₂ and CH₄. ALF shows a remarkable CO₂ capacity of 86.2 cm³ g^-1 and record-high CO₂/C₂H₂ and CO₂/CH₄ uptake ratios. The inverse CO₂/C₂H₂ separation and exclusive CO₂ capture performance from hydrocarbons are validated via adsorption isotherms and dynamic breakthrough experiments. Notably, the hydrogen-confined pore cavities with appropriate dimensional size provide an ideal pore chemistry to specifically match CO₂ via a hydrogen bonding mechanism, with all hydrocarbons rejected. This molecular recognition mechanism is unveiled by in situ Fourier-transform infrared spectroscopy, X-ray diffraction studies, and molecular simulations.

Boosting the C2H2/CO2 Separation Performance of Metal-Organic Frameworks through Fluorine Substitution

A pair of metal-organic frameworks (MOFs) of JXNU-15 (formulated as [Co₆(μ₃-OH)₆(BTB)₂(BPY)₃]_n, BTB^3- = benzene-1,3,5-tribenzoate and BPY = 4,4'-bipyridine) and its fluorinated JXNU-15(F) ([Co₆(μ₃-OH)₆(SFBTB)₂(BPY)₃]_n) based on the fluorous 1,3,5-tri(3,5-bifluoro-4-carboxyphenyl)benzene (SFBTB^3-) ligands were presented. The detailed comparisons of the acetylene/carbon dioxide (C₂H₂/CO₂) separation abilities between the isostructural JXNU-15(F) and JXNU-15 were presented. In comparison with the parent JXNU-15, the higher C₂H₂ uptake, larger adsorption selectivity of the C₂H₂/CO₂ (50/50) mixture, and enhanced C₂H₂/CO₂ separation performance endow JXNU-15(F) with highly efficient C₂H₂/CO₂ separation performance, which is demonstrated by singe-component gas adsorptions and dynamic gas mixture breakthrough experiments. The fluorine substituents exert the crucial effects on the enhanced C₂H₂/CO₂ separation ability of JXNU-15(F) and play the dominant role in the C₂H₂-framework interactions, as uncovered by computational simulations. This work illustrates a powerful fluorine substitution strategy for boosting C₂H₂/CO₂ separation ability for MOFs.

Engineering Pore Environments of Sulfate-Pillared Metal-Organic Framework for Efficient C2 H2 /CO2 Separation with Record Selectivity

Engineering pore environments exhibit great potential in improving gas adsorption and separation performances but require specific means for acetylene/carbon dioxide (C₂ H₂ /CO₂ ) separation due to their identical dynamic diameters and similar properties. Herein, a novel sulfate-pillared MOF adsorbent (SOFOUR-TEPE-Zn) using 1,1,2,2-tetra(pyridin-4-yl) ethene (TEPE) ligand with dense electronegative pore surfaces is reported. Compared to the prototype SOFOUR-1-Zn, SOFOUR-TEPE-Zn exhibits a higher C₂ H₂ uptake (89.1 cm³ g^-1 ), meanwhile the CO₂ uptake reduces to 14.1 cm³ g^-1 , only 17.4% of that on SOFOUR-1-Zn (81.0 cm³ g^-1 ). The high affinity toward C₂ H₂ than CO₂ is demonstrated by the benchmark C₂ H₂ /CO₂ selectivity (16 833). Furthermore, dynamic breakthrough experiments confirm its application feasibility and good cyclability at various flow rates. During the desorption cycle, 60.1 cm³ g^-1 C₂ H₂ of 99.5% purity or 33.2 cm³ g^-1 C₂ H₂ of 99.99% purity can be recovered by stepped purging and mild heating. The simulated pressure swing adsorption processes reveal that 75.5 cm³ g^-1 C₂ H₂ of 99.5+% purity with a high gas recovery of 99.82% can be produced in a counter-current blowdown process. Modeling studies disclose four favorable adsorption sites and dense packing for C₂ H₂ .

Cooperative CO2 adsorption mechanism in a perfluorinated CeIV-based metal organic framework

Adsorbents able to uptake large amounts of gases within a narrow range of pressure, i.e., phase-change adsorbents, are emerging as highly interesting systems to achieve excellent gas separation performances with little energy input for regeneration. A recently discovered phase-change metal-organic framework (MOF) adsorbent is F4_MIL-140A(Ce), based on Ce^IV and tetrafluoroterephthalate. This MOF displays a non-hysteretic step-shaped CO₂ adsorption isotherm, reaching saturation in conditions of temperature and pressure compatible with real life application in post-combustion carbon capture, biogas upgrading and acetylene purification. Such peculiar behaviour is responsible for the exceptional CO₂/N₂ selectivity and reverse CO₂/C₂H₂ selectivity of F4_MIL-140A(Ce). Here, we combine data obtained from a wide pool of characterisation techniques - namely gas sorption analysis, in situ infrared spectroscopy, in situ powder X-ray diffraction, in situ X-ray absorption spectroscopy, multinuclear solid state nuclear magnetic resonance spectroscopy and adsorption microcalorimetry - with periodic density functional theory simulations to provide evidence for the existence of a unique cooperative CO₂ adsorption mechanism in F4_MIL-140A(Ce). Such mechanism involves the concerted rotation of perfluorinated aromatic rings when a threshold partial pressure of CO₂ is reached, opening the gate towards an adsorption site where CO₂ interacts with both open metal sites and the fluorine atoms of the linker.

Ultramicroporous iron-isonicotinate MOFs combining size-exclusion kinetics and thermodynamics for efficient CO2/N2 gas separation

Two ultramicroporous 2D and 3D iron-based Metal-Organic Frameworks (MOFs) have been obtained by solvothermal synthesis using different ratios and concentrations of precursors. Their reduced pore space decorated with pendant pyridine from tangling isonicotinic ligands enables the combination of size-exclusion kinetic gas separation, due to their small pores, with thermodynamic separation, resulting from the interaction of the linker with CO₂ molecules. This combined separation results in efficient materials for dynamic breakthrough gas separation with virtually infinite CO₂/N₂ selectivity in a wide operando range and with complete renewability at room temperature and ambient pressure.

Fe-MOF with U-Shaped Channels for C2H2/CO2 and C2H2/C2H4 Separation

The development of high-performance adsorbents is critical for the low-energy separation of acetylene. Herein, we synthesized an Fe-MOF (MOF, metal-organic framework) with U-shaped channels. The adsorption isotherms of C₂H₂, C₂H₄, and CO₂ show that the adsorption capacity of acetylene is significantly larger than that of the other two gases. Meanwhile, the actual separation performance was verified by breakthrough experiments, indicating the potential to separate C₂H₂/CO₂ and C₂H₂/C₂H₄ mixtures at normal temperatures. Grand Canonical Monte Carlo (GCMC) simulation demonstrates that the framework with U-shaped channels interacts more strongly with C₂H₂ than with C₂H₄ and CO₂. The high C₂H₂ uptake and low adsorption enthalpy highlight Fe-MOF as a promising candidate for C₂H₂/CO₂ separation with a low regeneration energy.

Low-concentration CO2 capture using metal-organic frameworks - current status and future perspectives

The ever-increasing atmospheric CO₂ level is considered to be the major cause of climate change. Although the move away from fossil fuel-based energy generation to sustainable energy sources would significantly reduce the release of CO₂ into the atmosphere, it will most probably take time to be fully implemented on a global scale. On the other hand, capturing CO₂ from emission sources or directly from the atmosphere are robust approaches that can reduce the atmospheric CO₂ concentration in a relatively short time. Here, we provide a perspective on the recent development of metal-organic framework (MOF)-based solid sorbents that have been investigated for application in CO₂ capture from low-concentration (<10 000 ppm) CO₂ sources. We summarized the different sorbent engineering approaches adopted by researchers, both from the sorbent development and processing viewpoints. We also discuss the immediate challenges of using MOF-based CO₂ sorbents for low-concentration CO₂ capture. MOF-based materials, with tuneable pore properties and tailorable surface chemistry, and ease of handling, certainly deserve continued development into low-cost, efficient CO₂ sorbents for low-concentration CO₂ capture.

Optimizing Acetylene Sorption through Induced-fit Transformations in a Chemically Stable Microporous Framework

Developing practical storage technologies for acetylene (C₂ H₂ ) is important but challenging because C₂ H₂ is useful but explosive. Here, a novel metal-organic framework (MOF) (FJI-H36) with adaptive channels was prepared. It can effectively capture C₂ H₂ (159.9 cm³  cm^-3 ) at 1 atm and 298 K, possessing a record-high storage density (561 g L^-1 ) but a very low adsorption enthalpy (28 kJ mol^-1 ) among all the reported MOFs. Structural analyses show that such excellent adsorption performance comes from the synergism of active sites, flexible framework, and matched pores; where the adsorbed-C₂ H₂ can drive FJI-H36 to undergo induced-fit transformations step by step, including deformation/reconstruction of channels, contraction of pores, and transformation of active sites, finally leading to dense packing of C₂ H₂ . Moreover, FJI-H36 has excellent chemical stability and recyclability, and can be prepared on a large scale, enabling it as a practical adsorbent for C₂ H₂ . This will provide a useful strategy for developing practical and efficient adsorbents for C₂ H₂ storage.

Pore Environment Optimization of Microporous Metal-Organic Frameworks with Huddled Pyrazine Pillars for C2H2/CO2 Separation

Metal-organic frameworks (MOFs) have been proven promising in addressing many critical issues related to gas separation and purification. However, it remains a great challenge to optimize the pore environment of MOFs for purification of specific gas mixtures. Herein, we report the rational construction of three isostructural microporous MOFs with the 4,4',4"-tricarboxyltriphenylamine (H₃TCA) ligand, unusual hexaprismane Ni₆O₆ cluster, and functionalized pyrazine pillars [PYZ-x, x = -H (DZU-10), -NH₂ (DZU-11), and -OH (DZU-12)], where the building blocks of Ni₆O₆ clusters and huddled pyrazine pillars are reported in porous MOFs for the first time. These building blocks have enabled the resulting materials to exhibit good chemical stability and variable pore chemistry, which thus contribute to distinct performances toward C₂H₂/CO₂ separation. Both single-component isotherms and dynamic column breakthrough experiments demonstrate that DZU-11 with the PYZ-NH₂ pillar outperforms its hydrogen and hydroxy analogues. Density functional theory calculations reveal that the higher C₂H₂ affinity of DZU-11 over CO₂ is attributed to multiple electrostatic interactions between C₂H₂ and the framework, including strong C≡C···H-N (2.80 Å) interactions. This work highlights the potential of pore environment optimization to construct smart MOF adsorbents for some challenging gas separations.

Increased CO2 Affinity and Adsorption Selectivity in MOF-801 Fluorinated Analogues

The novel Zr^IV-based perfluorinated metal-organic framework (PF-MOF) [Zr₆O₄(OH)₄(TFS)₆] (ZrTFS) was prepared under solvent-free conditions using the commercially available tetrafluorosuccinic acid (H₂TFS) as a bridging ditopic linker. Since H₂TFS can be seen as the fully aliphatic and perfluorinated C₄ analogue of fumaric acid, ZrTFS was found to be isoreticular to zirconium fumarate (MOF-801). The structure of ZrTFS was solved and refined from X-ray powder diffraction data. Despite this analogy, the gas adsorption capacity of ZrTFS is much lower than that of MOF-801; in the former, the presence of bulky fluorine atoms causes a considerable window size reduction. To have PF-MOFs with more accessible porosity, postsynthetic exchange (PSE) reactions on (defective) MOF-801 suspended in H₂TFS aqueous solutions were carried out. Despite the different H₂TFS concentrations used in the PSE process, the exchanges yielded two mixed-linker materials of similar minimal formulae [Zr₆O₄(μ₃-OH)₄(μ₁-OH)_2.08(H₂O)_2.08(FUM)_4.04(HTFS)_1.84] (PF-MOF1) and [Zr₆O₄(μ₃-OH)₄(μ₁-OH)_1.83(H₂O)_1.83(FUM)_4.04(HTFS)_2.09] (PF-MOF2) (FUM^2- = fumarate), where the perfluorinated linker was found to fully replace the capping acetate in the defective sites of pristine MOF-801. CO₂ and N₂ adsorption isotherms collected on all samples reveal that both CO₂ thermodynamic affinity (isosteric heat of adsorption at zero coverage, Q_st) and CO₂/N₂ adsorption selectivity increase with the amount of incorporated TFS^2-, reaching the maximum values of 30 kJ mol^-1 and 41 (IAST), respectively, in PF-MOF2. This confirms the beneficial effect coming from the introduction of fluorinated linkers in MOFs on their CO₂ adsorption ability. Finally, solid-state density functional theory calculations were carried out to cast light on the structural features and on the thermodynamics of CO₂ adsorption in MOF-801 and ZrTFS. Due to the difficulties in modeling a defective MOF, an intermediate structure containing both linkers in the framework was also designed. In this structure, the preferential CO₂ adsorption site is the tetrahedral pore in the "UiO-66-like" structure. The extra energy stabilization stems from a hydrogen bond interaction between CO₂ and a hydroxyl group on the inorganic cluster.

Fluorinated metal-organic frameworks for gas separation

Fluorinated metal-organic frameworks (F-MOFs) as fast-growing porous materials have revolutionized the field of gas separation due to their tunable pore apertures, appealing chemical features, and excellent stability. A deep understanding of their structure-performance relationships is critical for the synthesis and development of new F-MOFs. This critical review has focused on several strategies for the precise design and synthesis of new F-MOFs with structures tuned for specific gas separation purposes. First, the basic principles and concepts of F-MOFs as well as their structure, synthesis and modification and their structure to property relationships are studied. Then, applications of F-MOFs in adsorption and membrane gas separation are discussed. A detailed account of the design and capabilities of F-MOFs for the adsorption of various gases and the governing principles is provided. In addition, the exceptional characteristics of highly stable F-MOFs with engineered pore size and tuned structures are put into perspective to fabricate selective membranes for gas separation. Systematic analysis of the position of F-MOFs in gas separation revealed that F-MOFs are benchmark materials in most of the challenging gas separations. The outlook and future directions of the science and engineering of F-MOFs and their challenges are highlighted to tackle the issues of overcoming the trade-off between capacity/permeability and selectivity for a serious move towards industrialization.

Precise Introduction of Single Vanadium Site into Indium-Organic Framework for CO2 Capture and Photocatalytic Fixation

The capture and fixation of CO₂ under mild conditions is a cost-effective route to reduce greenhouse gases, but it is challenging because of the low conversion and selectivity issues. Metal-organic frameworks (MOFs) are promising in the fields of adsorption and catalysis because of their structural tunability and variability. However, the precise structural design of MOFs is always pursued and elusive. In this work, a metal-mixed MOF (SNNU-97-InV) was designed by precisely introducing single vanadium site into the isostructural In-MOF (SNNU-97-In). The single V sites clearly change the interactions between the MOF framework and CO₂ molecules, leading to a 71.3% improvement in the CO₂ adsorption capacity. At the same time, the enhanced light absorption enables SNNU-97-InV to efficiently convert CO₂ into cyclic carbonates (CCs) with epoxides under illumination. Controlled experiments showed that the promoted performance of SNNU-97-InV may be that the V═O site can more easily combine with CO₂ and convert them into an intermediate state under illumination, and the possible mechanism was thus speculated.

Ultramicroporous material based parallel and extended paraffin nano-trap for benchmark olefin purification

Selective paraffin capture from olefin/paraffin mixtures could afford high-purity olefins directly, but suffers from the issues of low separation selectivity and olefin productivity. Herein, we report an ultramicroporous material (PCP-IPA) with parallel-aligned linearly extending isophthalic acid units along the one-dimensional channel, realizing the efficient production of ultra-high purity C₂H₄ and C₃H₆ (99.99%). The periodically expanded and parallel-aligned aromatic-based units served as a paraffin nano-trap to contact with the exposed hydrogen atoms of both C₂H₆ and C₃H₈, as demonstrated by the simulation studies. PCP-IPA exhibits record separation selectivity of 2.48 and separation potential of 1.20 mol/L for C₃H₈/C₃H₆ (50/50) mixture, meanwhile the excellent C₂H₆/C₂H₄ mixture separation performance. Ultra-high purity C₃H₆ (99.99%) and C₂H₄ (99.99%) can be directly obtained through fixed-bed column from C₃H₈/C₃H₆ and C₂H₆/C₂H₄ mixtures, respectively. The record C₃H₆ productivity is up to 15.23 L/kg from the equimolar of C₃H₈/C₃H₆, which is 3.85 times of the previous benchmark material, demonstrating its great potential for those important industrial separations.

Efficient Adsorption of Acetylene over CO2 in Bioinspired Covalent Organic Frameworks

Rational design of covalent organic frameworks (COFs) to broaden their diversity is highly desirable but challenging due to the limited, expensive, and complex building blocks, especially compared with other easily available porous materials. In this work, we fabricated two novel bioinspired COFs, namely, NUS-71 and NUS-72, using reticular chemistry with ellagic acid and triboronic acid-based building blocks. Both COFs with AB stacking mode exhibit high acetylene (C₂H₂) adsorption capacity and excellent separation performance for C₂H₂/CO₂ mixtures, which is significant but rarely explored using COFs. The impressive affinities for C₂H₂ appear to be related to the sandwich structure formed by C₂H₂ and the host framework via multiple host-guest interactions. This work not only represents a new avenue for the construction of low-cost COFs but also expands the variety of the COF family using natural biochemicals as building blocks for broad application.

Efficient Separation of Trace SO2 from SO2/CO2/N2 Mixtures in a Th-Based MOF

The emission of sulfur dioxide (SO₂) from flue gases is harmful since trace SO₂ impairs human health and the natural environment. Therefore, developing new metal organic frameworks (MOFs) to capture this toxic molecule is of great importance in flue gas desulfurization. In this work, we synthesized a new MOF, namely, ECUT-Th-60, which consists of two distinct channels (3.0 Å × 4.1 Å and 2.3 Å × 4.8 Å). It shows SO₂ uptakes of around 2.5 mmol/g at 0.1 kPa and 3.35 mmol/g at 1 bar, which are higher than those of CO₂ and N₂ under identical conditions. Both simulated and experimental breakthrough tests proved that ECUT-Th-60 can separate trace SO₂ from SO₂/CO₂ mixtures. Impressively, complete separation of SO₂ from SO₂/CO₂/N₂ mixtures under both dry and humid conditions was also proved in ECUT-Th-60, predicting its potential application in flue gas desulfurization.

Efficient One-Step Purification of C1 and C2 Hydrocarbons over CO2 in a New CO2-Selective MOF with a Gate-Opening Effect

Removing CO2 impurity is an essential industrial process in the purification of hydrocarbons. The most promising strategy is the one-step collection of high-purity hydrocarbons by employing CO2-selective adsorbents, which requires improving the CO2 adsorption and separation behavior of adsorbents, especially the low-pressure performance under actual industrial conditions. Herein, we constructed a new flexible metal-organic framework [Zn(odip)0.5(bpe)0.5(CH3OH)]·0.5NMF·H2O (1) (H4odip = 5,5'-oxydiisophthalic acid, bpe = 1,2-bi(4-pyridyl)ethylene, and NMF = N-methylformamide) containing rich ether O adsorption sites in the channels that exhibits remarkable adsorption capacity for CO2 (118.7 cm3 g-1) due to the only gate-opening-type abrupt adsorption of CO2 at room temperature. Its low affinity for other competing gases enables it to deliver high selectivity for the adsorption of CO2 over C1 and C2 hydrocarbons. For equimolar mixtures of CO2-CH4 and CO2-C2H2, the selectivities are 376.0 and 13.2, respectively. Molecular simulations disclose more abundant adsorption sites for CO2 than hydrocarbons in 1. The breakthrough separation performances combined with remarkable stability and recyclability further verify that 1 is a promising adsorbent that can efficiently extract high-purity hydrocarbons through selective capture of CO2.

Recent progress on porous MOFs for process-efficient hydrocarbon separation, luminescent sensing, and information encryption

Metal-organic frameworks (MOFs), as an emerging class of porous materials, excel in designability, regulatability, and modifiability in terms of their composition, topology, pore size, and surface chemistry, thus affording a huge potential for addressing environment and energy-related challenges. In particular, MOFs can be applied as porous adsorbents for the purification of industrially important hydrocarbons through certain process-efficient separation schemes based on selectivity-reversed adsorption and multicomponent separation. Moreover, the vast combination possibilities and controllable and engineerable luminescent units of MOFs make them a versatile platform to develop functionally tailored materials for luminescent sensing and optical data encryption. In this feature article, we summarize the recent progress in the use of porous MOFs for the separation and purification of acetylene (C₂H₂) and ethylene (C₂H₄) based on selectivity-reversed adsorption and multicomponent separation strategies. Moreover, we highlight the advances over the past three years in the field of MOF-based luminescent materials for thermometry, turn-on sensing, and information encryption.