Porous anionic indium-organic framework with enhanced gas and vapor adsorption and separation ability

Isoreticular Metal-Organic Frameworks with Aromatic Pores and Dimethylammonium Cations Enable Separation of Light Hydrocarbons and Xenon/Krypton

The separation of C2-C3 hydrocarbons from methane in natural gas and xenon/krypton purification are crucial yet challenging industrial processes. Herein, we report two isoreticular metal-organic frameworks, ZJU-89 and ZJU-90, featuring aromatic pore environments and dimethylammonium cations, that synergistically enhance the separation of these industrially relevant gas mixtures. ZJU-90 exhibits an exceptional separation performance, achieving C3H8/CH4 and C2H6/CH4 ideal adsorbed solution theory (IAST) selectivities of 1065 and 48, respectively, at ambient conditions, outperforming most reported adsorbent materials. Remarkably, ZJU-90 enables the recovery of >99.95% purity methane from a C3H8/C2H6/CH4 mixture in a single adsorption step. The material also demonstrates the efficient separation of xenon from krypton, even at low concentrations. The superior performance stems from the aromatic rings decorating the pore walls and the free dimethylammonium cations in the channels, which provide an ideal chemical environment for the selective binding of C2H6, C3H8, and Xe through multiple C-H···π interactions and van der Waals forces, as elucidated by theoretical calculations. This work highlights the power of reticular chemistry in designing materials with synergistic pore environments for efficient separations.

Solvent-Induced In(III)-MOFs with Controllable Interpenetration Degree Performing High-Efficiency Separation of CO2/N2 and CO2/CH4

Herein, three In(III)-based metal-organic frameworks (In-MOFs) with different degrees of interpenetration (DOI), namely In-MOF-1, In-MOF-2, and In-MOF-3, constructed by In3+ and Y-shaped ligands 4,4',4″-s-triazine-2,4,6-triyltribenzoate (H3TATB), are successfully synthesized through the ionothermal/solvothermal method. Subsequently, three novel In-MOFs, including noninterpenetration polycatenation, 2-fold interpenetrated, and 4-fold interpenetrated structure, are employed as the platform for systematically investigating the separation efficiency of CO2/N2, CO2/CH4, and CO2/CH4/N2 mixture gas system. Among them, In-MOF-2 shows the highest CO2 uptake capacities at 298 K and simultaneously possesses the low adsorption enthalpy of CO2 (26.4 kJ/mol at low coverage), a feature desirable for low-energy-cost adsorbent regeneration. The CO2/N2 (v: v = 15/85) selectivity of In-MOF-2 reaches 37.6 (at 298 K and 1 bar), also revealing outstanding selective separation ability from flue gases and purifying natural gas, affording a unique robust separation material as it has moderate DOI and pore size. In-MOF-2 shows exceptional stability and feasibility to achieve reproducibility. Aperture adjustment makes In-MOF-2 a versatile platform for selectively capturing CO2 from flue gases or purifying natural gas.

Porous MOF Featuring 2D Intersecting Channels Based on a Pentanuclear Mn5(COO)10CO3 Cluster with Upgrading of Pipeline Natural Gas

Natural gas plays a crucial role in daily and industrial production, but the impurities contained in natural gas limit its further use. It is very important to develop adsorbents that can separate CH4 from multicomponent mixtures, but there are still many challenges and problems. Herein, a novel porous MOF {[Mn5(pbdia)2(CO3)(H2O)2] ↔ 5H2O ↔ 2DMF}n (pbdia = 2,2'-(5-carboxy-1,3-phenylene)bis(oxy) diterephthalic acid) was successfully synthesized based on a flexible pentacarboxylic acid ligand and a unique pentanuclear Mn5(COO)10CO3 cluster. The MOF reveals a 3D porous structure with 2D intersecting channels, which shows high C3H8, C2H6, and CO2 adsorption capacities and affinities over CH4. Moreover, the ideal adsorption solution theory selectivities of C3H8/CH4, C2H6/CH4, and CO2/CH4 can reach 263.0, 27.0, and 7.7, respectively, suggesting a potential for removing the low content of C3H8, C2H6, and CO2 from pipeline natural gas, which was further confirmed by breakthrough curves and GCMC simulations.

A Microporous Zn(bdc)(ted)0.5 with Super High Ethane Uptake for Efficient Selective Adsorption and Separation of Light Hydrocarbons

Separating light hydrocarbons (C2H6, C3H8, and C4H10) from CH4 is challenging but important for natural gas upgrading. A microporous metal-organic framework, Zn(bdc)(ted)0.5, based on terephthalic acid (bdc) and 1,4-diazabicyclo[2.2.2]octane (ted) ligands, is synthesized and characterized through various techniques, including powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and porosity analysis. The adsorption isotherms of light hydrocarbons on the material are measured and the isosteric adsorption heats of CH4, C2H6, C3H8, and C4H10 are calculated. The prediction of C2-4/C1 adsorption selectivities is accomplished using ideal adsorbed solution theory (IAST). The results indicate that the material exhibits exceptional characteristics, including a Brunauer-Emmett-Teller (BET) surface area of 1904 m2/g and a pore volume of 0.73 cm3/g. Notably, the material demonstrates remarkable C2H6 adsorption capacities (4.9 mmol/g), while CH4 uptake remains minimal at 0.4 mmol/g at 298 K and 100 kPa. These findings surpass those of most reported MOFs, highlighting the material's outstanding performance. The isosteric adsorption heats of C2H6, C3H8, and C4H10 on the Zn(bdc)(ted)0.5 are higher than CH4, suggesting a stronger interaction between C2H6, C3H8, and C4H10 molecules and Zn(bdc)(ted)0.5. The molecular simulation reveals that Zn(bdc)(ted)0.5 prefers to adsorb hydrocarbon molecules with richer C-H bonds and larger polarizability, which results in a stronger dispersion force generated by an adsorbent-adsorbate induced polarization effect. Therefore, the selectivity of C4H10/CH4 is up to 180 at 100 kPa, C3H8/CH4 selectivity is 67, and the selectivity of C2H6/CH4 is 13, showing a great potential for separating C2-4 over methane.

Superior Selective CO2 Adsorption and Separation over N2 and CH4 of Porous Carbon Nitride Nanosheets: Insights from GCMC and DFT Simulations

Development of high-performance materials for the capture and separation of CO₂ from the gas mixture is significant to alleviate carbon emission and mitigate the greenhouse effect. In this work, a novel structure of C₉N₇ slit was developed to explore its CO₂ adsorption capacity and selectivity using Grand Canonical Monte Carlo (GCMC) and Density Functional Theory (DFT) calculations. Among varying slit widths, C₉N₇ with the slit width of 0.7 nm exhibited remarkable CO₂ uptake with superior CO₂/N₂ and CO₂/CH₄ selectivity. At 1 bar and 298 K, a maximum CO₂ adsorption capacity can be obtained as high as 7.06 mmol/g, and the selectivity of CO₂/N₂ and CO₂/CH₄ was 41.43 and 18.67, respectively. In the presence of H₂O, the CO₂ uptake of C₉N₇ slit decreased slightly as the water content increased, showing better water tolerance. Furthermore, the underlying mechanism of highly selective CO₂ adsorption and separation on the C₉N₇ surface was revealed. The closer the adsorption distance, the stronger the interaction energy between the gas molecule and the C₉N₇ surface. The strong interaction between the C₉N₇ nanosheet and the CO₂ molecule contributes to its impressive CO₂ uptake and selectivity performance, suggesting that the C₉N₇ slit could be a promising candidate for CO₂ capture and separation.

Integrating Self-Partitioned Pore Space and Amine Functionality into an Aromatic-Rich Coordination Framework with Ph Stability for Effective Purification of C2 Hydrocarbons

A great demand for high-purity C₂ hydrocarbons calls for the development of chemically stable porous materials for the effective isolation of C₂ hydrocarbons from CH₄ and CO₂. However, such separations are challenged by their similar physiochemical parameters and have not been systematically studied to date. In this work, we reported a cadmium-based rod-packing coordination framework compound ZJNU-140 of a new 5,6,7-c topology built up from a custom-designed tricarboxylate ligand. The metal-organic framework (MOF) features an aromatic-abundant pore surface, uncoordinated amine functionality, and self-partitioned pore space of suitable size. These structural characteristics act synergistically to provide the MOF with both selective recognition ability and the confinement effect toward C₂ hydrocarbons. As a result, the MOF displays promising potential for adsorptive separation of C₂-CH₄ and C₂-CO₂ mixtures. The IAST-predicted C₂/CH₄ and C₂/CO₂ adsorption selectivities, respectively, fall in the ranges of 7.3-10.2 and 2.1-2.9 at 298 K and 109 kPa. The real separation performance was also confirmed by dynamic breakthrough experiments. In addition, the MOF can maintain skeleton intactness in aqueous solutions with a wide pH range of 3-11, as confirmed by powder X-ray diffraction (PXRD) and isotherm measurements, showing no loss of framework integrity and porosity. The excellent hydrostability, considerable uptake capacity, impressive adsorption selectivity, and mild regeneration make ZJNU-140 a promising adsorbent material applied for the separation and purification of C₂ hydrocarbons.

Framework Adaptability and Concerted Structural Response in a Bismuth Metal-Organic Framework Catalyst

Bismuth metal-organic frameworks (MOFs) as heterogeneous catalysts are scarce, and there is little knowledge on the influence of the MOF features on their resulting activity and behavior. Here, we present the synthesis, characterization, and catalytic activity in the one-pot multicomponent Strecker reaction with ketones of three new MOFs prepared with the combination of indium or bismuth and 4,4',4'',4'''-methanetetrayltetrabenzoic acid. One of them, denoted BiPF-7, is very robust and chemically stable, and demonstrates a high activity in the formation of the desired α-aminonitriles. The interaction of the catalytic substrates with the metal centers in this MOF has been crystallographically characterized, showcasing a concerted framework adaptability process that involves structural changes in framework components that are not directly involved in the binding of the guests.

MOF Pillaring Method: Ligand-to-Ligand and Axial-to-Axial Cross-Linking of "Paddlewheels"

By shortening the previous shortest tetracarboxylate ligand, the first ligand-to-ligand and axial-to-axial pillaring method was realized in the prototype MOF NTUniv-56 (NTUniv = Nantong University), which exhibit a rare (2,4,6)-connected net with a new topology and interesting gas adsorption performance.

Functional Porous Ionic Polymers as Efficient Heterogeneous Catalysts for the Chemical Fixation of CO2 under Mild Conditions

The development of efficient and metal-free heterogeneous catalysts for the chemical fixation of CO2 into value-added products is still a challenge. Herein, we reported two kinds of polar group (-COOH, -OH)-functionalized porous ionic polymers (PIPs) that were constructed from the corresponding phosphonium salt monomers (v-PBC and v-PBH) using a solvothermal radical polymerization method. The resulting PIPs (POP-PBC and POP-PBH) can be used as efficient bifunctional heterogeneous catalysts in the cycloaddition reaction of CO2 with epoxides under relatively low temperature, ambient pressure, and metal-free conditions without any additives. It was found that the catalytic activities of the POP-PBC and POP-PBH were comparable with the homogeneous catalysts of Me-PBC and PBH and were higher than that of the POP-PPh3-COOH that was synthesized through a post-modification method, indicating the importance of the high concentration catalytic active sites in the heterogeneous catalysts. Reaction under low CO2 concentration conditions showed that the activity of the POP-PBC (with a conversion of 53.8% and a selectivity of 99.0%) was higher than that of the POP-PBH (with a conversion of 32.3% and a selectivity of 99.0%), verifying the promoting effect of the polar group (-COOH group) in the porous framework. The POP-PBC can also be recycled at least five times without a significant loss of catalytic activity, indicating the high stability and robustness of the PIPs-based heterogeneous catalysts.

A Microporous MOF Constructed by Cross-Linking Helical Chains for Efficient Purification of Natural Gas and Ethylene

Natural gas (NG) and ethylene (C₂H₄) are two raw materials of significant value for manufacturing versatile fine chemicals and/or polymers, and thus the development of solid adsorbing agents such as metal-organic frameworks (MOFs) applied to their depuration is very crucial but remains highly challenging. In this research, we designed and synthesized a ligand containing mixed N and O coordination donors, which was solvothermally assembled with Cu(II) ions to generate a microporous MOF. X-ray crystallography revealed that the title MOF incorporates one-dimensional (1D) homochiral helical chains that are datively cross-linked to form open channels in the three-periodic coordination framework. Furthermore, the behaviors of C₁-C₂ hydrocarbons and carbon dioxide (CO₂) adsorbed in the title MOF were systematically investigated, revealing its promising potential for the purification of both NG and C₂H₄. At 109 kPa and 298 K, the C₂/methane (CH₄), CO₂/CH₄, and acetylene (C₂H₂)/C₂H₄ adsorption selectivities are impressive, reaching as high as 62.9, 28.6, and 3.5, respectively. This work represents a unique MOF based on cross-linked homochiral helical chains exhibiting dual-function separation potentials for NG and C₂H₄ purifications.

Efficient Gas and VOC Separation and Pesticide Detection in a Highly Stable Interpenetrated Indium-Organic Framework

The new indium-based organic framework {(Me₂NH₂)[In(BDPO)]·DMF·2H₂O}_n (1) was successfully constructed by using the oxalamide group modified ligand N,N'-bis(isophthalic acid)oxalamide (H₄BDPO). This framework presents a 2-fold interpenetrating structural characteristic, and the unique polar pore environment leads to a high capture ability for CO₂, C₂H_n and CH₃OH and good separation ability for CO₂ and C₂H_n over CH₄ as well as for CH₃OH over C₂H₅OH, which was further verified by an ideal adsorbed solution theory (IAST) calculation. Theoretical simulations pointed out the possible adsorption sites of different adsorbed gases in 1. In addition, the excellent chemical stability and strong luminescence of 1 give it an effective selective detection ability for 2,6-dichloro-4-nitroaniline (DCN) in water with a low detection limit of 3.85 ppm, and the detection mechanism is discussed in detail.

Modifying a partial corn-sql layer-based (3,3,3,3,4,4)-c topological MOF by substitution of OH- with Cl- and its highly selective adsorption of C2 hydrocarbons over CH4

Modifying VNU-18 (a MOF with a partial cone-sql layer pillared by the chains of pillars decorated with OH^-) by substitution of OH^- with Cl^-, a new isoreticular structure, [Cu₆(L)₅·(Cl^-)₂·H₂O·4DMF]·4DMF·6(H₂O) (SNNU-Bai67, SNNU-Bai = Shaanxi Normal University Bai's group), has been successfully synthesized. Furthermore, we deeply investigated the selective C2 hydrocarbon separation properties of SNNU-Bai67 and VNU-18 by single-component gas adsorption experiments, breakthrough experiments and simulation studies. They exhibit highly selective adsorption for C2 hydrocarbons over CH₄ compared to many reported MOFs for the separation of C2 hydrocarbons from CH₄, due to the suitable pore sizes of the partial corn sql-layer built from the isophthalic acid analogy and Cu-paddlewheel units. Interestingly, with the counterion of OH^- in VNU-18 tuned by Cl^- in SNNU-Bai67, the adsorption uptake values of C2 hydrocarbons were apparently improved by 15.0% for C₂H₂, 20.4% for C₂H₄ and 25.3% for C₂H₆, respectively, while the IAST selectivities of C2 hydrocarbons/CH₄ were still nearly the same, which may be because the synergistic effect of interactions of H_C2/1O_COO, H_C2/1N/C_Py, H_PyC_C2, ππ or H_C2C_C2 between the gas molecules and the framework is enhanced by the weaker polarity of Cl^- decorating the framework.

Creative Construction of a Series of Chiral 3D Indium-Organic Frameworks with a umy Topology

Using 2,2'-R₂-biphenyl-4,4'-dicarboxylic acid to bind with a cis-[InO₄(μ₂-OH)₂] octahedron, three novel chiral 3D indium-organic frameworks, [In(μ₂-OH)L] [1, L¹, R = N(CH₃)₂; 2, L², R = OCH₃; 3, L³, R = CH₃], have been hydrothermally synthesized without chiral reagents. Crystal structure analyses reveal that 1-3 show an unprecedented 4-connected umy topology with the Schläfli symbol (4²·6⁴). 1 exhibits high water stability and good sorption selectivity of CO₂ over N₂, while 3 displays high C₂H₂, C₂H₄, and C₂H₆ uptake capacity at 273 K.

Microporous polycarbazole frameworks with large conjugated π systems for cyclohexane separation from cyclohexane-containing mixtures

Two microporous polycarbazole frameworks with large conjugated π systems were constructed for cyclohexane separation from cyclohexane-containing mixtures.

A porous anionic zinc(ii) metal–organic framework for gas adsorption, selective uptake of dyes and sensing of Fe3+ by Tb3+ ion encapsulation

A 3D anionic, porous MOF exhibits selective adsorption of cationic dyes and can be used as a fast-response fluorescence sensor for the detection of Fe3+ ions by Tb3+ ion encapsulation.

Building a robust 3D Ca-MOF by a new square Ca4O SBU for purification of natural gas

For the first time, a new square Ca4O SBU is introduced into a 3D Ca-MOF, ([MeNH2]2[Ca4O(MTB)2(EtOH)4])·(solvent)n (1), to generate a (4,8)-connected flu-topology structure. Compound 1 exhibits selective adsorption of C3 and C2 hydrocarbons and CO2 over CH4 with especially high IAST selectivities for C3 hydrocarbons over CH4 (at 15/85 and 50/50 ratio) at 298K and 1 bar.

Highly Selective Separation of C3H8 and C2H2 from CH4 within Two Water-Stable Zn5 Cluster-Based Metal-Organic Frameworks

Adopting the mixed ligands approach, two water-stable Zn₅ cluster-based MOFs, [Zn₁₀(TZ)₁₂(TADIPA)₂(DMF)₄]·DMF·6H₂O (JLU-MOF66) and [Zn₁₀(TZ)₁₂(TPTA)₂(DMA)₂]·2DMA·4H₂O (JLU-MOF67), have been constructed (H₄TADIPA = 5,5'-(1H-1,2,4-triazole-3,5-diyl)diisophthalic acid, H₄TPTA = [1,1':3',1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid, and HTZ = 1H-[1,2,3]triazole). Both compounds with [Zn₅(TZ)₆] clusters exhibit extraordinary stability (pH = 2-11) and selectivity of C₃H₈/CH₄ (308 for JLU-MOF66, and 287 for JLU-MOF67). Compared to JLU-MOF67, JLU-MOF66 with functional groups exhibits higher CO₂ and C₂H₂ uptake capacity and excellent selective separation for C₂H₂/CH₄ (86, 1:1). Such high separation and chemical stability render them as promising materials for industrial applications.

Record Complexity in the Polycatenation of Three Porous Hydrogen-Bonded Organic Frameworks with Stepwise Adsorption Behaviors

Hydrogen-bonded organic frameworks (HOFs) show great potential in many applications, but few structure-property correlations have been explored in this field. In this work, we report that self-assembly of a rigid and planar ligand gives rise to flat hexagonal honeycomb motifs which are extended into undulated two-dimensional (2D) layers and finally generate three polycatenated HOFs with record complexity. This kind of undulation is absent in the 2D layers built from a very similar but nonplanar ligand, indicating that a slight torsion of ligand produces overwhelming structural change. This change delivers materials with unique stepwise adsorption behaviors under a certain pressure originating from the movement between mutually interwoven hexagonal networks. Meanwhile, high chemical stability, phase transformation, and preferential adsorption of aromatic compounds were observed in these HOFs. The results presented in this work would help us to understand the self-assembly behaviors of HOFs and shed light on the rational design of HOF materials for practical applications.

Exceptionally effective benzene/cyclohexane separation using a nitro-decorated metal-organic framework

Using a series of isoreticular MOFs with void connections of varying diameters, the selective separation of benzene and cyclohexane in both liquid and vapor phases is shown. The driving force of the highly efficient adsorption process is the formation of weak interactions between the adsorbed benzene molecules and the host framework.

Irreversible tautomerization as a powerful tool to access unprecedented functional porous organic polymers with a tris(β-keto-hydrazo)cyclohexane subunit (TKH-POPs)

Irreversible tautomerization could lead to fascinating functional porous organic polymers such as TKH-POPs comprising tris(β-keto-hydrazo)-cyclohexane subunit.

Three stable dinuclear [M2(OH)0.5(NO3)0.5(RCOO)2(RN)4] (M = Cu, Ni) based metal–organic frameworks with high CO2 adsorption and selective separation for O2/N2 and C3H8/CH4

Three isostructural and stable MOFs have been constructed. All the three compounds with high-density OMSs exhibit high performances for CO₂ capture and selective separation.

Energy transfer on a two-dimensional antenna enhances the photocatalytic activity of CO2 reduction by metal-organic layers

Excited state energies on a two-dimensional light-harvesting metal-organic layer (MOL) are efficiently transported to Re- and Ir-based reaction centers for converting CO₂ to CO or HCOOH. Such energy transfer enhances the photocatalytic CO₂ reduction activity because it enables multiple photo-electron injections in a short time period in the photocatalysis.

A Microporous Metal-Organic Framework Supramolecularly Assembled from a CuII Dodecaborate Cluster Complex for Selective Gas Separation

A novel 3D metal-organic framework BSF-1 based on the closo-dodecaborate cluster [B₁₂ H₁₂ ]^2- was readily prepared at room temperature by supramolecular assembly of CuB₁₂ H₁₂ and 1,2-bis(4-pyridyl)acetylene. The permanent microporous structure was studied by X-ray crystallography, powder X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and gas sorption. The experimental and theoretical study of the gas sorption behavior of BSF-1 for N₂ , C₂ H₂ , C₂ H₄ , CO₂ , C₃ H₈ , C₂ H₆ , and CH₄ indicated excellent separation selectivities for C₃ H₈ /CH₄ , C₂ H₆ /CH₄ , and C₂ H₂ /CH₄ as well as moderately high separation selectivities for C₂ H₂ /C₂ H₄ , C₂ H₂ /CO₂ , and CO₂ /CH₄ . Moreover, the practical separation performance of C₃ H₈ /CH₄ and C₂ H₆ /CH₄ was confirmed by dynamic breakthrough experiments. The good cyclability and high water/thermal stability render it suitable for real industrial applications.

An indium–organic framework for the efficient storage of light hydrocarbons and selective removal of organic dyes

An anionic indium–organic framework has been successfully prepared for the efficient absorption and separation of C2–C3 hydrocarbons from CH₄ as well as highly selective uptake of cationic organic dyes from anionic or neutral dyes.

A lactam-functionalized copper bent diisophthalate framework displaying significantly enhanced adsorption of CO2 and C2H2 over CH4

The first lactam-functionalized MOF based on a bent diisophthalate ligand was constructed, displaying significantly enhanced uptake and selectivity for C₂H₂ and CO₂ over CH₄.

A heterometallic metal–organic framework based on multi-nuclear clusters exhibiting high stability and selective gas adsorption

Porous In/Tb-CBDA has been successfully synthesized in the light of the heterometallic cooperative crystallization (HCC) approach. In/Tb-CBDA with high thermal and chemical stability exhibited high performance for gas storage and separation.

Amino-functionalized Cu-MOF for efficient purification of methane from light hydrocarbons and excellent catalytic performance

Amino-functionalized Cu-MOF for the efficient purification of methane from light hydrocarbons and excellent catalytic performance.

Photophysical properties of cationic dyes captured in the mesoscale channels of micron-sized metal-organic framework crystals

The optical properties of dye molecules in confined spaces can differ from the solution phase due to confinement effects. Pre-organized mesoscale channels of metal-organic frameworks (MOFs) are very suited for hosting various dyes, and the robust frameworks often render the encapsulated dyes with certain preferential geometries, which are different from those found in solution. Furthermore, pre-organized open channels can efficiently guide the uniform and unique spatial distribution of dye molecules in a controlled manner, which are otherwise difficult to achieve. Thus, sufficiently large dye molecules can avoid the formation of complex aggregates when captured inside open channels. In contrast, small dye molecules can form well-defined dimers or aggregates. The resulting dye-encapsulated MOFs can display unusual photophysical properties of the captured dyes. An anionic framework of In-BTB with mesoscale 3D channels is utilized for the efficient encapsulation of various cationic dyes through cation-exchange processes. Six different cationic dyes are encapsulated in the anionic framework of In-BTB, and their crystal structures are completely solved. Novel photophysical properties of these spatially distributed dye molecules in dye@In-BTBs are investigated.