Programmed fluorine binding engineering in anion-pillared metal-organic framework for record trace acetylene capture from ethylene

A new type of C2H2 binding site in a cis-bridging hexafluorosilicate ultramicroporous material that offers trace C2H2 capture

Hybrid ultramicroporous materials (HUMs) comprising hexafluorosilicate (SiF6 2-, SIFSIX) and their variants are promising physisorbents for trace acetylene (C2H2) capture and separation, where the inorganic anions serve as trans-bridging pillars. Herein, for the first time, we report a strategy of fluorine binding engineering in these HUMs via switching the coordination mode of SIFSIX from traditional trans to rarely explored cis. The first example of a rigid HUM involving cis-bridging SIFSIX, SIFSIX-bidmb-Cu (bidmb = 1,4-bis(1-imidazolyl)-2,5-dimethylbenzene), is reported. The resulting self-interpenetrated network is found to be water stable and exhibits strong binding to C2H2 but weak binding to C2H4 and CO2, affording a high Q st of 55.7 kJ mol-1 for C2H2, a high C2H2 uptake of 1.86 mmol g-1 at 0.01 bar and high ΔQ st values. Breakthrough experiments comprehensively demonstrate that SIFSIX-bidmb-Cu can efficiently capture and recover C2H2 from 50/50 or 1/99 C2H2/CO2 and C2H2/C2H4 binary mixtures. In situ single crystal X-ray diffraction (SCXRD) combined with dispersion-corrected density functional theory (DFT-D) calculations reveals that the C2H2 binding site involves two cis-SiF6 2- anions in close proximity (F⋯F distance of 7.16 Å), creating a new type of molecular trap that affords six uncoordinated fluoro moieties to chelate each C2H2 via sixfold C-H⋯F hydrogen bonds. This work therefore provides a new strategy for binding site engineering with selective C2H2 affinity to enable trace C2H2 capture.

A "turn-on" fluorescent sensor for the selective detection of erythromycin in aqueous solution

The accurate and rapid detection of erythromycin (ERY) is of great significance to environmental protection and human health. Herein, a "turn-on" fluorescent sensor was developed for the quantitative detection of ERY in aqueous solution. The probe Cu-BDC-NH2 exhibits weak blue emission due to the ligand-to-metal charge transfer (LMCT) effect. Upon the addition of ERY, the fluorescence intensity increases by 436%, whereas other similar antibiotics lead to fluorescence quenching. The sensing mechanisms were thoroughly investigated by powder X-ray diffraction, fluorescence lifetime measurements, UV-vis spectroscopy and X-ray photoelectron spectroscopy. Owing to the excellent selectivity and sensitivity, test strips based on the probe were further prepared to evaluate the practical applicability in real samples.

Engineering Supramolecular Binding Sites in an Ultrastable and Hydrophobic Metal-Organic Framework for C2H6/C2H4 Separation

The separation of ethane (C2H6) from ethylene (C2H4) is critical for obtaining polymer-grade C2H4. Adsorptive separation with C2H6-selective MOFs offers a viable alternative to energy-intensive cryogenic distillation, enabling the direct production of high-purity C2H4. In this study, we developed an ultrastable ethane-selective metal-organic framework, UiO-67-(CH3)2, which demonstrates enhanced C2H6 adsorption (4.10 mmol g-1 at 1 bar and 298 K), higher C2H6/C2H4 selectivity of 1.70, and an increased C2H6/C2H4 adsorption ratio of 1.53 compared to unmodified UiO-67. GCMC simulations demonstrate that C2H6 forms more C-H···π interactions with the surrounding benzene rings and more C-H···C interactions with methyl groups compared to C2H4, highlighting the synergistic effects of supramolecular interactions. Furthermore, the hydrophobic pore environment also minimizes water interference, with exceptionally low water uptake (0.019 g g-1 at 60% RH), ensuring robust separation capacity under high humid conditions. The introduction of methyl groups not only significantly enhances C2H6 adsorption performance and C2H6/C2H4 separation selectivity but also improves material's hydrophobicity.

Electrostatic Potential Matching in an Anion-Pillared Framework for Benchmark Hexafluoroethane Purification from Ternary Mixture

One-step purification of CF3CF3 from ternary CF3CH2F/CF3CHF2/CF3CF3 mixture is crucial since its vital role in the semiconductor industry. However, efficient separation of chemically inert CF₃CF₃ remains challenging due to the difficulty in creating specific recognition sites in porous materials. In this work, we report the first example of anion-pillared MOFs to the separation of fluorinated electronic specialty gases, utilizing the unique electrostatic potential matching in the bipolar pores of SIFSIX-1-Cu to realize a benchmark CF3CH2F/CF3CHF2/CF3CF3 separation. SIFSIX-1-Cu exhibits the highest CF3CH2F and CF3CHF2 adsorption capacity at 0.01 bar, as well as the highest CF3CH2F/CF3CF3 and CF3CHF2/CF3CF3 IAST selectivity. Additionally, high-purity (≥ 99.995%) CF3CF3 with record productivity (882.9 L kg-1) can be acquired through one-step breakthrough experiment of CF3CH2F/CF3CHF2/CF3CF3 (5/5/90). Theoretical calculations further reveal that the coexistence of electronegative SiF6 2- and partially electropositive H sites promotes SIFSIX-1-Cu to effectively anchor CF3CH2F and CF3CHF2 through multiple supramolecular interactions.

Robust Anion-Pillared Ultramicroporous Material for C2H2/C2H4 Separation with High C2H2 Uptake and Selectivity

Removing trace amounts of C2H2 from C2H2/C2H4 mixtures for C2H4 purification is crucial but extremely challenging. In this work, by introducing SiF62- with specific recognition for C2H2, we constructed a robust adsorbent, FJI-W88, with a high C2H2 adsorption capacity and excellent C2H2/C2H4 separation selectivity. FJI-W88 not only exhibits ultrahigh C2H2 uptake at 0.01 bar (2.80 mmol g-1) but also shows exceptional C2H2/C2H4 (1/99) IAST selectivity of 698. Column breakthrough experiments further demonstrate that FJI-W88 can obtain C2H4 of high purity (≥99.95%) and high yield (230.0 mol kg-1) from C2H2/C2H4 (1/99) mixtures. Additionally, the C2H2/C2H4 (1/99) separation performance of FJI-W88 is basically unaffected under harsh conditions, such as high temperature and humidity.

Pore Space Partition Enabled by Lithium(I) Chelation of a Metal-Organic Framework for Benchmark C2H2/CO2 Separation

Adsorptive separation of acetylene (C2H2) from carbon dioxide (CO2) offers a promising approach to purify C2H2 with low-energy footprints. However, the development of ideal adsorbents with simultaneous high C2H2 adsorption and selectivity remains a great challenge due to their very small molecular sizes and physical properties. Herein, we report a lithium(I)-chelation strategy for pore space partition (PSP) in a microporous MOF (Li+@NOTT-101-(COOH)2) to achieve simultaneous high C2H2 uptake and selectivity. The chelation model of Li+ ions within the framework was visually identified by single-crystal X-ray diffraction studies. The immobilized Li+ ions were found to have two functions: (1) partitioning large pore cages into smaller ones while maintaining high surface area and (2) providing specific binding sites to selectively take up C2H2 over CO2. The resulting Li+@NOTT-101-(COOH)2 exhibits a rare combination of a simultaneous high C2H2 capture capacity (205 cm3 g-1) and C2H2/CO2 selectivity (13) at ambient conditions, far surpassing that of NOTT-101-(COOH)2 (148 cm3 g-1 and 3.8, respectively) and most top-tier materials reported. Theoretical calculations and gas-loaded SCXRD studies reveal that the chelated Li+ ions combined with the segmented small cages can selectively bind with a large amount of C2H2 through the unique π-complexation, accounting for the improved C2H2 uptake and selectivity. Breakthrough experiments validated its excellent separation capacity for actual C2H2/CO2 mixtures, providing one of the highest C2H2 productivities of 118.9 L kg-1 (>99.5% purity) in a single adsorption-desorption cycle.

Ionic porous materials: from synthetic strategies to applications in gas separation and catalysis

Ionic porous materials possess a unique combination of tunable pore sizes and task-specific interactions between guest molecules and the charged frameworks, which endow them with versatility across diverse domains in chemistry and materials science. Significant advancements in their applications for gas separation and catalysis have been achieved in recent years due to the incorporation of ionic functionalities and ultra-microporous structures that enable molecular-scale recognition of guest molecules. This review summarizes recent advancements in the synthetic strategies of ionic porous materials, establishing design guidelines for the incorporation of ionic moieties into the backbone to fine-tune pore sizes and chemistry. It highlights the synergistic interplay of task-specific interactions with custom-designed pore structures in key applications, including adsorption separation, membrane separation, and gas conversion. Additionally, it examines structure-property relationships, offering deeper insights into enhancing performance. The report also addresses the current challenges in the practical application of these materials. Finally, the review provides future perspectives on ionic porous materials from both scientific and industrial viewpoints. Overall, this review aims to provide insights into pore structure and chemistry, supporting the precise placement of ionic functionalities.

Catalytic Efficacy of a 2D Chemically Robust MOF for the Synthesis of Bioactive Diindolylmethane (DIM)-Based Drug Molecules

Synthesis of biologically and pharmaceutically important drugs via organic transformations in one pot under mild conditions with efficient catalysts is of significant interest in terms of practical utility. Though metal-organic frameworks (MOFs) prove their efficiencies in various catalytic reactions, synthesis of drug molecules employing MOF catalysts is still in its early stage, in fact, restricted to only 1,4-Dihydropyridines (1,4-DHP) based drug molecules synthesis. Although the Friedel-Crafts alkylation (FCA) reaction is one of the oldest reactions with a significant impact on drug molecules synthesis, surprisingly this reaction triggered by MOF catalyst is largely unexplored. Herein, we report a robust framework, MOF: IITKGP-55, synthesized solely in aqueous medium, which exhibits its superior catalytic efficiencies for one-pot FCA reaction with the well tolerance of various substrate scopes. Most importantly, based on this catalytic reaction, three drug molecules with bioactive diindolylmethane (DIM) core are synthesized for the first time, which was never realized by employing any sort of heterogeneous catalysts. Moreover, Arundine drug is crystallized and an in-depth crystallographic analysis is performed. The superior catalytic efficiencies with excellent framework robustness highlight the potentiality of the developed framework and unwrap a new avenue for drug molecule synthesis via FCA reaction by employing heterogeneous catalysts.

In Situ Stimulus Response Study on the Acetylene/Ethylene Purification Process in MOFs

Efficient removal of acetylene (C2H2) impurities from polymer-grade ethylene (C2H4) in a simple, clean manner remains a challenging goal in industry. The use of porous materials such as metal-organic frameworks (MOFs) is promising for this aim but the acquisition of high purification performance is still hindered by few knowledge on the purification process because the previous conclusions were derived basically from the non-breakthrough tests or ignored the influence of structural difference (crystal structure, morphology, or defect). Here we propose an unprecedented in situ stimulus response strategy to minimize the influence of structural difference, obtain the gas-loading crystal structures of the same MOF before and after light or heat stimulation, directly observe the evolution of pore charge distribution and pore⋅⋅⋅gas interactions under light/heat induction, and finally summarizes the favorable structure for highly efficient purification of C2H4. This study opens a new route to understand the relationship between the structure and separation performance for porous materials.

An MOF-Based Single-Molecule Propylene Nanotrap for Benchmark Propylene Capture from Ethylene

Highly selective capture and separation of propylene (C3H6) from ethylene (C2H4) presents one of the most crucial processes to obtain pure C2H4 in the petrochemical industry. The separation performance of current physisorbents is commonly limited by insufficient C3H6 binding affinity, resulting in poor low-pressure C3H6 uptakes or inadequate C3H6/C2H4 selectivities. Herein, we realize a unique single-molecule C3H6 nanotrap in an ultramicroporous MOF material (Co(pyz)[Pd(CN)4], ZJU-74a-Pd), exhibiting the benchmark C3H6 capture capacity at low-pressure regions. This MOF-based nanotrap features the sandwichlike strong multipoint binding sites and the perfect size match with C3H6 molecules, providing an ultrastrong C3H6 binding affinity with the maximal Q st value (55.8 kJ mol-1). This affords the nanotrap to exhibit one of the highest C3H6 uptakes at low pressures (60.5 and 103.8 cm3 cm-3 at 0.01 and 0.1 bar) and record-high C3H6/C2H4 selectivity (23.4). Theoretical calculations reveal that the perfectly size-matched pore cavities combined with sandwichlike multibinding sites enable this single-molecule C3H6 nanotrap to maximize the C3H6 binding affinity, mainly accounting for its record low-pressure C3H6 capture capacity and selectivity. Breakthrough experiments further confirm its excellent separation capacity for actual 1/99 and 50/50 C3H6/C2H4 mixtures, affording the remarkably high pure C2H4 productivities of 17.1 and 3.4 mol kg-1, respectively.

Two amino-functionalized metal-organic frameworks with different topologies for C2H2/C2H4 separation

The rational design of metal-organic framework adsorbents is crucial for target gas separation. Herein, we report two three-dimensional MOFs with different topologies by regulating metal ions with amino-functionalized V-type ligands. Adsorption isotherms and Grand Canonical Monte Carlo simulation reveal that UPC-122 with channel-cavity structure has the potential to separate C2H2/C2H4 at room temperature with a separation ratio of 2.35 (50/50).

Achieving Record C2H2 Packing Density for Highly Efficient C2H2/C2H4 Separation with a Metal-Organic Framework Prepared by a Scalable Synthesis in Water

Adsorptive C2H2/C2H4 separation using metal-organic frameworks (MOFs) has emerged as a promising technology for the removal of C2H2 (acetylene) impurity (1 %) from C2H4 (ethylene). The practical application of these materials involves the optimization of separation performance as well as development of scalable and green production protocols. Herein, we report the efficient C2H2/C2H4 separation in a MOF, Cu(OH)INA (INA: isonicotinate) which achieves a record C2H2 packing density of 351 mg cm-3 at 0.01 bar through high affinity towards C2H2. DFT (density functional theory) calculations reveal the synergistic binding mechanism through pore confinement and the oxygen sites in pore wall. The weakly basic nature of binding sites leads to a relatively low heat of adsorption (Qst) of approximately 36 kJ/mol, which is beneficial for material regeneration and thermal management. Furthermore, a scalable and environmentally friendly synthesis protocol with a high space-time yield of 544 kg m-3 day-1 has been developed without using any modulating agents. This material also demonstrates enduring separation performance for multiple cycles, maintaining its efficacy after exposure to water or air for three months.

Ultra-High Purity and Productivity Separation of CO2 and C2H2 from CH4 in Rigid Layered Ultramicroporous Material

Efficiently obtaining both high-purity gas-phase and adsorbed-phase products in a single physisorption process presents the challenge of simultaneously achieving high selectivity and uptake and rapid diffusion in adsorbents. With a focus on natural gas purification and high-purity acetylene production, we report for the first time that the synergistic ligand/anion binding mode and multiple diffusion pathways in a robust 2D layered ultramicroporous framework (ZUL-100) enable unprecedented carbon dioxide/methane and acetylene/methane separation performance. Taking advantage of its rich anion, functional ligand ,and rigid 3D interpenetrated ultramicroporous channels, ZUL-100 achieved record IAST selectivities for equimolar carbon dioxide/methane (3.2 × 105) and acetylene/methane (1.7 × 1010) mixtures, accompanied by record dynamic uptakes of carbon dioxide (3.10 mmol/g) and acetylene (4.79 mmol/g), respectively. The strong affinity and fast mass transfer of carbon dioxide and acetylene on ZUL-100 were systematically elucidated by a combination of in situ FTIR, single-crystal XRD, kinetic tests, and DFT-D adsorption/diffusion modeling. In particular, high-purity (≥99.999%) methane and carbon dioxide (acetylene) can both be obtained on ZUL-100 through a single adsorption-desorption cycle, with exceptional productivity (2.81-4.22 mmol/g of methane, 2.96 mmol/g of carbon dioxide, and 4.31 mmol/g of acetylene) and high yield (95.5% for carbon dioxide and 90.0% for acetylene).

Cross-Linking CdSO4-Type Nets with Hexafluorosilicate Anions to Form an Ultramicroporous Material for Efficient C2H2/CO2 and C2H2/C2H4 Separation

A 44.610.8 topology hybrid ultramicroporous material (HUM), {[Cu1.5F(SiF6)(L)2.5]·G}n, (L = 4,4'-bisimidazolylbiphenyl, G = guest molecules), 1, formed by cross-linking interpenetrated 3D four-connected CdSO4-type nets with hexafluorosilicate anions is synthesized and evaluated in the context of gas sorption and separation herein. 1 is the first HUM functionalized with two different types of fluorinated sites (SiF6 2- and F- anions) lining along the pore surface. The optimal pore size (≈5 Å) combining mixed and high-density electronegative fluorinated sites enable 1 to preferentially adsorb C2H2 over CO2 and C2H4 by hydrogen bonding interactions with a high C2H2 isosteric heat of adsorption (Qst) of ≈42.3 kJ mol-1 at zero loading. The pronounced discriminatory sorption behaviors lead to excellent separation performance for C2H2/CO2 and C2H2/C2H4 that surpasses many well-known sorbents. Dynamic breakthrough experiments are conducted to confirm the practical separation capability of 1, which reveal an impressive separation factor of 6.1 for equimolar C2H2/CO2 mixture. Furthermore, molecular simulation and density functional theory (DFT) calculations validate the strong binding of C2H2 stems from the chelating fix of C2H2 between SiF6 2- anion and coordinated F- anion.

Single-Molecule Traps in Covalent Organic Frameworks for Selective Capture of C2H2 from C2H4-Rich Gas Mixtures

Removing trace amounts of acetylene (C2H2) from ethylene (C2H4)-rich gas mixtures is vital for the supply of high-purity C2H4 to the chemical industry and plastics sector. However, selective removal of C2H2 is challenging due to the similar physical and chemical properties of C2H2 and C2H4. Here, we report a "single-molecule trap" strategy that utilizes electrostatic interactions between the one-dimensional (1D) channel of a covalent organic framework (denoted as COF-1) and C2H2 molecules to massively enhance the adsorption selectivity toward C2H2 over C2H4. C2H2 molecules are immobilized via interactions with the O atom of C=O groups, the N atom of C≡N groups, and the H atom of phenyl groups in 1D channels of COF-1. Due to its exceptionally high affinity for C2H2, COF-1 delivered a remarkable C2H2 uptake of 7.97 cm3/g at 298 K and 0.01 bar, surpassing all reported COFs and many other state-of-the-art adsorbents under similar conditions. Further, COF-1 demonstrated outstanding performance for the separation of C2H2 and C2H4 in breakthrough experiments under dynamic conditions. COF-1 adsorbed C2H2 at a capacity of 0.17 cm3/g at 2,000 s/g when exposed to 0.5 ml/min C2H4-rich gas mixture (99% C2H4) at 298 K, directly producing high-purity C2H4 gas at a rate of 3.95 cm3/g. Computational simulations showed that the strong affinity between C2H2 and the single-molecule traps of COF-1 were responsible for the excellent separation performance. COF-1 is also robust, providing a promising new strategy for the efficient removal of trace amounts of C2H2 in practical C2H4 purification.

Recent Advances of Multidentate Ligand-Based Anion-Pillared MOFs for Enhanced Separation and Purification Processes

As an important subclass of metal-organic frameworks (MOFs), anion-pillars MOFs (APMOFs) have recently exhibited exceptional performances in separation and purification processes. The adjustment of pore sizes and environments of APMOFs can be finely tuned through judicious combination of organic ligands, anion pillars, and metal ions. Compared to widely investigated anion pillars, organic ligands are more crucial as they allow for a broader range of pore sizes and environments at the nanometer scale. Furthermore, different from the bidentate ligand-based APMOFs that typically form three-dimensional (3D) frameworks with pcu topology, APMOFs constructed using multidentate nitrogen(N)-containing ligands (with a coordination number ≥ 3) offer opportunities to create APMOFs with diverse topologies. The larger dimensions and possible distortion of multidentate N-containing ligands prove advantageous for addressing multi-component hydrocarbon separations encompassing a broad spectrum of dynamic diameters. Therefore, this Review summarizes the structural characteristics of multidentate ligand-based APMOFs and their enhanced performances for gas separation and purification processes. Additionally, it discusses current challenges and prospects associated with constructing multidentate ligand-based APMOFs while providing prospects. This critical review will provide valuable insights and guides for designing and developing advanced multidentate ligand-based APMOF adsorbents.

Supramolecular Entanglement in a Hydrogen-Bonded Organic Framework Enables Flexible-Robust Porosity for Highly Efficient Purification of Natural Gas

The development of porous materials with flexible-robust characteristics shows some unique advantages to target high performance for gas separation, but remains a daunting challenge to achieve so far. Herein, we report a carboxyl-based hydrogen-bonded organic framework (ZJU-HOF-8a) with flexible-robust porosity for efficient purification of natural gas. ZJU-HOF-8a features a four-fold interpenetrated structure with dia topology, wherein abundant supramolecular entanglements are formed between the adjacent subnetworks through weak intermolecular hydrogen bonds. This structural configuration could not only stabilize the whole framework to establish the permanent porosity, but also enable the framework to show some flexibility due to its weak intermolecular interactions (so-called flexible-robust framework). The flexible-robust porosity of ZJU-HOF-8a was exclusively confirmed by gas sorption isotherms and single-crystal X-ray diffraction studies, showing that the flexible pore pockets can be opened by C3H8 and n-C4H10 molecules rather by C2H6 and CH4. This leads to notably higher C3H8 and n-C4H10 uptakes with enhanced selectivities than C2H6 over CH4 under ambient conditions, affording one of the highest n-C4H10/CH4 selectivities. The gas-loaded single-crystal structures coupled with theoretical simulations reveal that the loading of n-C4H10 can induce an obvious framework expansion along with pore pocket opening to improve n-C4H10 uptake and selectivity, while not for C2H6 adsorption. This work suggests an effective strategy of designing flexible-robust HOFs for improving gas separation properties.

Optimizing Trace Acetylene Removal from Acetylene/Ethylene Mixture in a Flexible Metal-Organic Framework by Crystal Downsizing

Improving the gas separation performance of metal-organic frameworks (MOFs) by crystal downsizing is an important but often overlooked issue. Here, we report three different-sized flexible ZUL-520 MOFs (according to the crystal size from large to small, the three samples are, respectively, named ZUL-520-0, ZUL-520-1, and ZUL-520-2) with the same chemical structure for optimizing trace acetylene (C2H2) removal from acetylene/ethylene (C2H2/C2H4) mixture. The three differently sized activated ZUL-520 (denoted as ZUL-520a) exhibited almost identical C2H2 uptake of 4.8 mmol/g at 100 kPa, while the C2H2 uptake at 1 kPa increased with a downsizing crystal. The C2H2 uptake of activated ZUL-520-2 (denoted as ZUL-520-2a) at 1 kPa was ∼55% higher than that of activated ZUL-520-0 (denoted as ZUL-520-0a). The adsorption isotherms and adsorption kinetics validated that gas adsorptive separation is governed not only by adsorption thermodynamics but also by adsorption kinetics. In addition, all three different-sized ZUL-520a MOFs showed high C2H2/C2H4 selectivity. Grand canonical Monte Carlo (GCMC) simulations and dispersion-corrected density functional theory (DFT-D) computations illustrated a plausible mechanism of C2H2 adsorption in MOFs. Importantly, breakthrough experiments demonstrated that ZUL-520a can effectively separate the C2H2/C2H4 (1/99, v/v) mixture and the C2H4 productivity obtained by ZUL-520-2a was much higher than that by ZUL-520-0a. Our work may provide an easy but powerful strategy for upgrading the performance of gas adsorptive separation in MOFs.

Recognition of C4 Olefins by an Ultramicroporous ftw-Type Yttrium-Based Metal-Organic Framework with Distorted Cages

Developing porous adsorbents for efficient separation of C4 olefins is significant but challenging in the petrochemical industry due to their similar molecular sizes and physical properties. The separation efficiency is often limited when separating C4 olefins by a single separation mechanism. Herein, an ultramicroporous yttrium-based MOF, Y-dbai, is reported featuring cage-like pores connected by small windows, for recognition and efficient separation of C4 olefins through a synergistic effect of thermodynamic and kinetic mechanisms. At 298 K and 1 bar, the adsorption capacities of Y-dbai for C4H6, 1-C4H8, and i-C4H8 are 2.88, 1.07, and 0.14 mmol g-1, respectively, indicating a molecular sieving effect toward i-C4H8. The C4H6/i-C4H8 and 1-C4H8/i-C4H8 uptake selectivities of Y-dbai are 20.6 and 7.6, respectively, outperforming most of the reported adsorbents. The static and kinetic adsorption experiments coupled with DFT calculations indicate the separation should be attributed to a combined effect of thermodynamically and kinetically controlled mechanism. Breakthrough experiments have confirmed the excellent separation capability of Y-dbai toward C4H6/1-C4H8, C4H6/i-C4H8, and C4H6/1-C4H8/i-C4H8 mixtures.

Tunable Low-Pressure Water Adsorption in Stable Multivariate Metal-Organic Frameworks for Boosting Water-Based Ultralow-Temperature-Driven Refrigeration

The green water-based adsorption refrigeration is considered as a promising strategy to realize near-zero-carbon cooling applications. Although many metal-organic frameworks (MOFs) have been developed as water adsorbents, their cooling performance are commonly limited by the insufficient water uptakes below P/P0 = 0.2. Herein, the development of multivariate MOFs (MTV-MOFs) is reported to highly modulate and boost the low-pressure water uptake for improving coefficient of performance (COP) for refrigeration. Through ligand exchange in the pristine MIL-125-NH2 , a series of MTV-MOFs with bare nitrogen sites are designed and synthesized. The resulting MIL-125-NH2 /MD-5% exhibits the significantly improved water uptake of 0.39 g g-1 at 298 K and P/P0 = 0.2, which is three times higher than MIL-125-NH2 (0.12 g g-1 ) and comparable to some benchmark materials including KMF-1 (0.4 g g-1 ) and MIP-200 (0.36 g g-1 ). Combined with its low-temperature regeneration, fast sorption kinetics and high stability, MIL-125-NH2 /MD-5% achieves one of the highest COP values (0.8) and working capacities (0.24 g g-1 ) for refrig-2 under an ultralow-driven temperature of 65 °C, which are higher than some best-performing MOFs such as MIP-200 (0.74 and 0.11 g g-1 ) and KMF-2 (0.62 and 0.16 g g-1 ), making it among the best adsorbents for efficient ultralow-temperature-driven refrigeration.

Tuning Multiple Counter-Anions in Porous Coordination Polymers with Topology for Acetylene/Ethylene Separation

The efficient separation of acetylene (C2H2) and ethylene (C2H4) is an important and complex process in the industry. Herein, we report a new family of lcy-topologic coordination frameworks (termed NTU-90 to NTU-92) with Cu3MF6 (M = Si, Ti, and Zr) nodes. These charged frameworks are compensated by different counterbalanced ions (MF62-, BF4-, and Cl-), yielding changes in the size of the window apertures. Among these frameworks, NTU-92-a (activated NTU-92) shows good adsorption selectivity of C2H2/C2H4 and also significant ability in recovering both highly pure C2H4 (99.95%) and C2H2 (99.98%). Our work not only presents a potential alternative for energy-saving purification of C2 hydrocarbons but also provides a new approach for tuning the function of charged porous materials.

Sulfate-Pillared Adsorbent for Efficient Acetylene Separation from Carbon Dioxide and Ethylene

The effective separation of acetylene (C2H2) from carbon dioxide (CO2) and ethylene (C2H4) presents considerable challenges in the petrochemical industry. In this work, we report a novel sulfate-pillared (SO4 2-) ultra-microporous material, denoted as SOFOUR-DPDS-Ni (SOFOUR = SO4 2-, 4-DPDS = 4,4'-dipyridyldisulfide), for efficient C2H2 capture from both CO2 and C2H4. The sulfate pillars play a crucial role in inducing robust negative electrostatic potentials within the intralayer cavities and interlayer channels, thereby facilitating the selective recognition of C2H2. As a result, SOFOUR-DPDS-Ni demonstrates a remarkable C2H2 adsorption capacity of 1.60 mmol g-1 at 0.01 bar, an exceptional selectivity of 174 for the 50/50 C2H2/CO2 mixture, and a high selectivity of 65 for the 1/99 C2H2/C2H4 mixture. These impressive metrics position SOFOUR-DPDS-Ni as a promising adsorbent for benchmark C2H2 separations. Dynamic breakthrough experiments validate its outstanding performance in separating C2H2 from both the CO2 and C2H4 mixtures. Computational simulations reveal the strong interactions between C2H2 and sulfate pillars, shedding light on the underlying mechanisms driving the adsorption process.

Thiadiazole-Functionalized Th/Zr-UiO-66 for Efficient C2H2/CO2 Separation

Adsorptive separation technology provides an effective approach for separating gases with similar physicochemical properties, such as the purification of acetylene (C2H2) from carbon dioxide (CO2). The high designability and tunability of metal-organic framework (MOF) adsorbents make them ideal design platforms for this challenging separation. Herein, we employ an isoreticular functionalization strategy to fine-tune the pore environment of Zr- and Th-based UiO-66 by the immobilization of the benzothiadiazole group via bottom-up synthesis. The functionalized UPC-120 exhibits an enhanced C2H2/CO2 separation performance, which is confirmed by adsorption isotherms, dynamic breakthrough curves, and theoretical simulations. The synergy of ligand functionalization and metal ion fine-tuning guided by isoreticular chemistry provides a new perspective for the design and development of adsorbents for challenging gas separation processes.

Microporous Fluorinated MOF with Multiple Adsorption Sites for Efficient Recovery of C2H6 and C3H8 from Natural Gas

Purifying C2H6/C3H8 from a ternary natural gas mixture through adsorption separation is an important but challenging process in the petrochemical industry. To address this challenge, the industry is exploring effective strategies for designing high-performance adsorbents. In this study, we present two metal-organic frameworks (MOFs), DMOF-TF and DMOF-(CF3)2, which have fluorinated pores obtained by substituting linker ligands in the host material. This pore engineering strategy not only provides suitable pore confinement but also enhances the adsorption capacities for C2H6/C3H8 by providing additional binding sites. Theoretical calculations and transient breakthrough experiments show that the introduction of F atoms not only improves the efficiency of natural gas separation but also provides multiple adsorption sites for C2H6/C3H8-framework interactions.

Water-stable metal-organic frameworks (MOFs): rational construction and carbon dioxide capture

Metal-organic frameworks (MOFs) are considered to be a promising porous material due to their excellent porosity and chemical tailorability. However, due to the relatively weak strength of coordination bonds, the stability (e.g., water stability) of MOFs is usually poor, which severely inhibits their practical applications. To prepare water-stable MOFs, several important strategies such as increasing the bonding strength of building units and introducing hydrophobic units have been proposed, and many MOFs with excellent water stability have been prepared. Carbon dioxide not only causes a range of climate and health problems but also is a by-product of some important chemicals (e.g., natural gas). Due to their excellent adsorption performances, MOFs are considered as a promising adsorbent that can capture carbon dioxide efficiently and energetically, and many water-stable MOFs have been used to capture carbon dioxide in various scenarios, including flue gas decarbonization, direct air capture, and purified crude natural gas. In this review, we first introduce the design and synthesis of water-stable MOFs and then describe their applications in carbon dioxide capture, and finally provide some personal comments on the challenges facing these areas.

Construction of Negative Electrostatic Pore Environments in a Scalable, Stable and Low-Cost Metal-organic Framework for One-Step Ethylene Purification from Ternary Mixtures

One-step separation of C2 H4 from ternary C2 mixtures by physisorbents remains a challenge to combine excellent separation performance with high stability, low cost, and easy scalability for industrial applications. Herein, we report a strategy of constructing negative electrostatic pore environments in a stable, low-cost, and easily scaled-up aluminum MOF (MOF-303) for efficient one-step C2 H2 /C2 H6 /C2 H4 separation. This material exhibits not only record high C2 H2 and C2 H6 uptakes, but also top-tier C2 H2 /C2 H4 and C2 H6 /C2 H4 selectivities at ambient conditions. Theoretical calculations combined with in situ infrared spectroscopy indicate that multiple N/O sites on pore channels can build a negative electro-environment to provide stronger interactions with C2 H2 and C2 H6 over C2 H4 . Breakthrough experiments confirm its exceptional separation performance for ternary mixtures, affording one of the highest C2 H4 productivity of 1.35 mmol g-1 . This material is highly stable and can be easily synthesized at kilogram-scale from cheap raw materials using a water-based green synthesis. The benchmark combination of excellent separation properties with high stability and low cost in scalable MOF-303 has unlocked its great potential in this challenging industrial separation.