Non-interpenetrated Metal-organic Framework Research Articles

Solvent-Driven Dynamics: Crafting Tailored Transformations of Cu(II)-Based MOFs.

Metal-organic frameworks (MOFs), a sort of crystalline porous coordination polymers composed of metal ions and organic linkers, have been intensively studied for their ability to take up nonpolar gas-phase molecules such as ethane and ethylene. In this context, interpenetrated MOFs, where multiple framework nets are entwined, have been considered promising materials for capturing nonpolar molecules due to their relatively higher stability and smaller micropores. This study explores a solvent-assisted reversible strategy to interpenetrate and deinterpenetrate a Cu(II)-based MOF, namely, MOF-143 (noninterpenetrated form) and MOF-14 (doubly interpenetrated forms). Interpenetration was achieved using protic solvents with small molecular sizes such as water, methanol, and ethanol, while deinterpenetration was accomplished with a Lewis-basic solvent, pyridine. Additionally, this study investigates the adsorptive separation of ethane and ethylene, which is a significant application in the chemical industry. The results showed that interpenetrated MOF-14 exhibited higher ethane and ethylene uptakes compared to the noninterpenetrated MOF-143 due to narrower micropores. Furthermore, we demonstrate that pristine MOF-14 displayed higher ethane selectivity than transformed MOF-14 from MOF-143 by identifying the "fraction of micropore volume" as a key factor influencing ethane uptake. These findings highlight the potential of controlled transformations between interpenetrated and noninterpenetrated MOFs, anticipating that larger MOF crystals with narrower micropores and higher crystallinity will be more suitable for selective gas capture and separation applications.

Deinterpenetration of IRMOF-9.

One of the iconic characteristics of metal-organic frameworks (MOFs) is the possesssion of guest-accessible pores. Increasing pore size has a direct and often beneficial impact on a MOF's adsorption and separation properties. However, as pore size increases, the resulting void spaces are often filled by interpenetrated frameworks, where one or more networks crystallize within the pore system of another identical network, reducing the MOF's free volume and pore size. Furthermore, due to the thermodynamic favorability of interpenetration during solvothermal synthesis, techniques to synthetically differentiate interpenetrated from non-interpenetrated MOFs are paramount. Herein we report the synthesis of deinterpenetrated IRMOF-9 via halide mediated deinterpenetrative conversion of Zn4O-derived IRMOF-9. IRMOF-9, when treated with ethylammonium bromide, is quasi-selectively etched, revealing the non-interpenetrated analogue, IRMOF-10 (deinterpenetrated IRMOF-9), which can be isolated prior to complete dissolution by the bromide solution. Dye adsorption, surface area and pore size distribution analysis, powder X-ray diffraction, and elemental analysis are consistent with successful deinterpenetration.

Synthesis, crystal structure and magnetic property of a 3D Cu-organic framework

The assembly of Cu(II) ion and a multidentate pyridine-azole ligand 3-(tetrazol-5-yl)-5-(pyrid-2-yl)-1,2,4-triazole (H2TPT), has resulted in an interesting 3D non-interpenetrating metal-organic framework, [Cu(TPT)]n (1). Compound 1 crystallizes in chiral P41212 space group with Flack parameter of −0.0268. The linkage of tetrazole groups of deprotonated TPT and Cu(II) centers generates the right-hand helical chains, and adjacent chains are further connected with each other, giving rise to a 3D intricate architecture. The compound was characterized by single-crystal X-ray diffraction, thermogravimetric analysis, elemental analysis, infrared spectroscopy and powder X-ray diffraction analysis. Moreover, the magnetic property of compound 1 has been investigated.

A Single-Crystal to Single-Crystal Conversion Scheme for a Two-Dimensional Metal–Organic Framework Bearing Linear Cd3 Secondary Building Units

The single-crystal to single-crystal (SCSC) conversion of metal–organic frameworks (MOFs) represents a facile route to new MOFs with structures and functionalities that are challenging to obtain by direct synthesis. However, conversion products are often structurally limited for a given precursor. We herein report that a two-dimensional (2D) MOF featuring a linear Cd3 cluster secondary building unit (SBU) converts into one type of three-dimensional (3D) interpenetrated and two types of 3D non-interpenetrated MOFs upon reaction with dipyridyl ligands. One of the interpenetrated 3D MOFs, in turn, undergoes either ligand substitution to give isoreticular interpenetrated MOFs, or ligand addition to give a self-penetrated 3D MOF. This rich SCSC conversion library is made possible by the inclined nature of the Cd3 SBU with respect to the 2D plane of the starting material to create an anisotropic environment around the SBU.

Near-White Light Emission from Lead(II) Metal-Organic Frameworks.

Reaction of bpy (bpy = 4,4'-bipyridine) with Pb(OAc)2·3H2O in DMF (DMF = dimethylformamide) afforded a metal-organic framework (MOF), [Pb2(μ-bpy)(μ-O2CCH3)2(μ-O2CCH3)2]·H2O (1). Reaction of bpy with Pb(O2CCF3)2 in a methanol and chloroform mixture furnished another MOF, [Pb(μ-bpy)(μ-O2CCF3)2]·1/2CHCl3 (2). However, the reaction of bpy with Pb(OAc)2·3H2O in the presence of trifluoroacetic acid in a similar reaction condition yielded a hydrogen-bonded zwitter-ionic complex of Pb(II), [Pb(bpy-H)2(O2CCF3)4] (3). All compounds have been characterized by single crystal X-ray crystallography, FT-IR, and 1H NMR spectroscopies. Compound 1 forms four heptacoordinated Pb(II) joined by (OCCH3)-O- linkages, resulting in a 3D noninterpenetrated MOF net with a four-connected uninodal sra (SrAl2) topology. However, in 2, tetra-connected Pb4(O2CCF3)8 cluster units are linked further through eight bpy ligands to furnish a doubly interpenetrated MOF with a new topology but having the very similar connectivity of 1, whereas 3 forms a zigzag hydrogen-bonded chain structure. The variation of carboxylate anions, pH of the reaction medium, and the ratio of the reactants profoundly affected the final topological structure of the compounds synthesized. The solid-state photoluminescence of 1-3 was investigated at room temperature. Interestingly 1, 2, and 3 achieved close to white light emission when excited at 329, 376, and 330 nm, respectively. The systematic understanding of the photophysical properties of analogous Pb-based compounds may open new perspectives for developing single-phase white-light-emitting materials using Pb(II) based MOFs.

Co₂ and Co₃ Mixed Cluster Secondary Building Unit Approach toward a Three-Dimensional Metal-Organic Framework with Permanent Porosity.

Large and permanent porosity is the primary concern when designing metal-organic frameworks (MOFs) for specific applications, such as catalysis and drug delivery. In this article, we report a MOF Co11(BTB)6(NO3)4(DEF)2(H2O)14 (1, H3BTB = 1,3,5-tris(4-carboxyphenyl)benzene; DEF = N,N-diethylformamide) via a mixed cluster secondary building unit (SBU) approach. MOF 1 is sustained by a rare combination of a linear trinuclear Co3 and two types of dinuclear Co2 SBUs in a 1:2:2 ratio. These SBUs are bridged by BTB ligands to yield a three-dimensional (3D) non-interpenetrated MOF as a result of the less effective packing due to the geometrically contrasting SBUs. The guest-free framework of 1 has an estimated density of 0.469 g cm−3 and exhibits a potential solvent accessible void of 69.6% of the total cell volume. The activated sample of 1 exhibits an estimated Brunauer-Emmett-Teller (BET) surface area of 155 m2 g−1 and is capable of CO2 uptake of 58.61 cm3 g−1 (2.63 mmol g−1, 11.6 wt % at standard temperature and pressure) in a reversible manner at 195 K, showcasing its permanent porosity.

A Permanently Porous Yttrium-Organic Framework Based on an Extended Tridentate Phosphine Containing Linker.

The metal-organic framework [Y(tbpp)]·nDMF (1) was synthesized from yttrium(III) nitrate and the tritopic linker tris(4'-carboxy[1,1'-biphenyl]-4-yl)phosphine (H3tbpp). The distance between the coordinating atoms of the carboxylate groups of the extended tridentate phosphine linker is more than 1.8 nm, resulting in an average pore dimension of 0.9 nm in the noninterpenetrated metal-organic framework. The material exhibits high thermal stability and permanent porosity after removal of guest molecules from the one-dimensional pore system. The desolvated compound adsorbs nitrogen, argon, hydrogen, and carbon dioxide. Favorable adsorption of CO2 over N2 is predicted using ideal adsorbed solution theory (IAST). The isosteric enthalpies of adsorption of H2 and CO2 of -7 and -22 kJ mol-1, respectively, are representative for metal-organic frameworks with no accessible strong host-guest binding sites, despite the bifunctional nature of the organic ligand. The absence of strong specific adsorption sites was confirmed by in situ powder synchrotron X-ray diffraction of the reversible isobaric CO2 sorption process. Analysis of the diffraction data indicates that the CO2 molecules in the pores are disordered and nonlocalized. Despite this, it was possible to quantify the evolution of the occupation of the pores. CO2 is adsorbed at an approximately constant below 320 K from 10% loading to full capacity at 195 K.

Aqueous microwave-assisted synthesis of non-interpenetrated metal-organic framework for room temperature cycloaddition of CO2 and epoxides

A multilinker non-interpenetrated metal-organic framework, UMCM-15, was synthesized by using microwave power as an alternative energy-efficient tool for the first time. The synergistic catalytic activity, when combined with a co-catalyst containing a strongly nucleophilic anion, was studied in the solventless room temperature cycloaddition between epoxides and CO2. Unlike previous reports on UMCM-15 synthesized in the high-boiling solvent dimethylformamide, low boiling water/ethanol mixture was used as the solvent herein. This approach holds potential as a sustainable green methodology. Crystal formation during the microwave-assisted (MW) synthesis was monitored at certain time intervals. The favorable role of non-interpenetrated pillared structures in promoting room temperature CO2-epoxide cycloaddition reactions was explained by comparing the catalytic efficiency of the three-linker extended pillar-layered non-interpenetrated UMCM-15 with its analogous pillared structures built from two- and three-fold interpenetrated ([Zn2(BDC)2(4,4′-bipy)] and [Zn2(NDC)2(4,4′-bipy)]) catalytic systems with a single dicarboxylate linker. The efficacy of the microwave-assisted UMCM-15(M) catalyst in cycloaddition reactions was proved by comparing the catalytic activity of UMCM-15(M) with that of the congener made by solvothermal synthesis, UMCM-15(S). In addition, a plausible mechanism for the synergistic operation of the Lewis acid sites and nucleophiles was suggested.

Activation-Dependent Breathing in a Flexible Metal-Organic Framework and the Effects of Repeated Sorption/Desorption Cycling.

A non-interpenetrated metal-organic framework with a paddle-wheel secondary building unit has been activated by direct thermal evacuation, guest exchange with a volatile solvent, and supercritical CO2 drying. Conventional thermal activation yields a mixture of crystalline phases and some amorphous content. Exchange with a volatile solvent prior to vacuum activation produces a pure breathing phase with high sorption capacity, selectivity for CO2 over N2 and CH4 , and substantial hysteresis. Supercritical drying can be used to access a guest-free open phase. Pressure-resolved differential scanning calorimetry was used to confirm and investigate a systematic loss of sorption capacity by the breathing phase as a function of successive cycles of sorption and desorption. A corresponding loss of sample integrity was not detectable by powder X-ray diffraction analysis. This may be an important factor to consider in cases where flexible MOFs are earmarked for industrial applications.

Exploring 3D non-interpenetrated metal–organic framework with malonate-bridged Co(II) coordination polymer: structural elucidation and theoretical study

ABSTRACTA Co(II)-based coordination polymer with tetranuclear cobalt(II)-malonate cluster has been easily generated by aqueous medium self-assembly from Cobalt(II) chloride hexahydrate and malonic acid. The structure exhibits a non-interpenetrating, highly undulating two-dimensional (2D) bi-layer network with (4,4) topology. The crystal structure is composed of infinite interdigitated 2D metal–organic bi-layers which extended to an intricate 3D framework through the interbilayer hydrogen bonds. We have studied energetically by means of Density Functional Theory (DFT) calculations the H-bonding interactions that connect the 2D metal–organic bi-layers. The finite theoretical models have been used to compute conventional O‒H∙∙∙O and unconventional C‒H∙∙∙O interactions which plays a key role to build 3D architecture.

Topology Conversions of Non-Interpenetrated Metal–Organic Frameworks to Doubly Interpenetrated Metal–Organic Frameworks

Non-interpenetrated three-dimensional (3D) metal–organic frameworks (MOFs) with both an interpenetration-favorable (3,5)-c hms topology and an interpenetration-unfavorable (3,5)-c gra topology are converted to doubly interpenetrated analogues with hms-c topology by thermal treatment, even in the absence of solvent. Depending on the conversion temperature and the properties of the pillaring ligand in the non-interpenetrated 3D MOF, which is based on two-dimensional sheets with 3-c hcb topology pillared by neutral ditopic linkers, the pillaring ligands in the interpenetrated MOFs produced are partially removed during the thermal conversions, leading to interpenetrated MOFs that simultaneously contain both micro- and mesopores.

A Highly Chemically Stable Metal–Organic Framework as a Luminescent Probe for the Regenerable Ratiometric Sensing of pH

A heteroatom-rich 3D noninterpenetrating metal-organic framework (MOF) Cd-EDDA constructed from an ethylene glycol ether bridging tetracarboxylate ligand H4 EDDA (5,5'-(ethane-1,2-diylbis(oxy))diisophthalic acid) shows good chemical resistance to both acidic and alkaline solutions with a pH ranging from 2.0 to 12.2. There is a corresponding ratiometric luminescence response to pH from 2.0 to 11.5, and the sensing mechanism is also discussed through ion chromatography and molecular force field-based calculations. Importantly, the probe can easily be regenerated simply by modulating the pH of the solution, thus being the first example of a regenerable MOF-based ratiometric luminescent probe for pH.

Non-Interpenetrated Metal-Organic Frameworks Based on Copper(II) Paddlewheel and Oligoparaxylene-Isophthalate Linkers: Synthesis, Structure, and Gas Adsorption.

Two metal-organic framework materials, MFM-130 and MFM-131 (MFM = Manchester Framework Material), have been synthesized using two oligoparaxylene (OPX) tetracarboxylate linkers containing four and five aromatic rings, respectively. Both fof-type non-interpenetrated networks contain Kagomé lattice layers comprising [Cu2(COO)4] paddlewheel units and isophthalates, which are pillared by the OPX linkers. Desolvated MFM-130, MFM-130a, shows permanent porosity (BET surface area of 2173 m(2)/g, pore volume of 1.0 cm(3)/g), high H2 storage capacity at 77 K (5.3 wt% at 20 bar and 2.2 wt% at 1 bar), and a higher CH4 adsorption uptake (163 cm(3)(STP)/cm(3) (35 bar and 298 K)) compared with its structural analogue, NOTT-103. MFM-130a also shows impressive selective adsorption of C2H2, C2H4, and C2H6 over CH4 at room temperature, indicating its potential for separation of C2 hydrocarbons from CH4. The single-crystal structure of MFM-131 confirms that the methyl substituents of the paraxylene units block the windows in the Kagomé lattice layer of the framework, effectively inhibiting network interpenetration in MFM-131. This situation is to be contrasted with that of the doubly interpenetrated oligophenylene analogue, NOTT-104. Calculation of the mechanical properties of these two MOFs confirms and explains the instability of MFM-131 upon desolvation in contrast to the behavior of MFM-130. The incorporation of paraxylene units, therefore, provides an efficient method for preventing network interpenetration as well as accessing new functional materials with modified and selective sorption properties for gas substrates.

A Noninterpenetrated Metal–Organic Framework Built from an Enlarged Tetracarboxylic Acid for Small Hydrocarbon Separation

A novel noninterpenetrated metal–organic framework [Cu2L(H2O)2]f·(DMA)18·(H2O)19 (ZJU-31, ZJU = ZheJiang University; H4L = 5′,5′′′′-(2,5-dimethoxy-1,4-phenylene)bis[1,1′:3′,1″-terphenyl]-4,4″-dicarboxylic acid; DMA = N,N-dimethylacetamide) has been synthesized and structurally characterized from an expanded organic linker. Interestingly, although the new linker is larger than the developed one for the construction of ZJU-30 with a doubly interpenetrated structure, the incorporation of a 1,4-dimethoxyphenyl group into the new linker enforces the formation of noninterpenetrated ZJU-31. Accordingly, the activated ZJU-31a shows a much higher porosity with a BET surface area of 1115 m2/g than ZJU-30a of 228 m2/g. ZJU-31a exhibits highly selective separation of C2 hydrocarbons over C1 methane at room temperature.

Robust metal–organic framework with [Mn3] clusters: Synthesis, structure and magnetic property

In this work, one novel three dimensional non-interpenetrated metal–organic framework {[Mn3(L)2(H2O)4]·2H2O·2DMF}n (1) was synthesized by a new tri-carboxylic ligand (H3L=3,5-Bis-[2-(4-carboxy-phenoxy)-ethoxy]-benzoic acid). Single crystal structural determination revealed that compound 1 possesses a stable 3D framework, containing linear tri-nuclear [Mn3] cluster as a node. The investigation on PXRD patterns in various solvents and TGA displays excellent solvents and thermal stability. Additionally, magnetic measurements indicate that antiferromagnetic interactions exist within compound 1.

Site-selective cyclometalation of a metal–organic framework

Although porous materials, including metal–organic frameworks (MOFs), can be functionalized using heterogeneous reactions (solution–solid, gas–solid), there are no reports that modify chemically identical sites in a spatially selective, periodic fashion. Herein, the cyclometalation of two non-interpenetrated MOFs and an interpenetrated MOF in the solid state is reported using [Ir(COD)(OCH3)]2 and [Rh(COD)(Cl)]2 (COD = 1,5-cyclooctadiene). Incredibly, the cyclometalation of the interpenetrated MOF occurs only on ligands that lie along, one crystallographic axis, providing an unprecedented example of site-selective postsynthetic modification (PSM). This represents a degree of control on the functionalization of a porous, material that has not been otherwise realized, and is achieved in part because of the crystalline, periodic nature of MOFs. Furthermore, it was found that the degree of cyclometalation, increases the sorption capacity of the interpenetrated MOF.

Novel (3,4,6)-Connected Metal–Organic Framework with High Stability and Gas-Uptake Capability

A microporous and noninterpenetrated metal-organic framework [Cu(3)(L)(2)(DABCO)(H(2)O)]·15H(2)O·9DMF (1) has been synthesized using two different ligands, [1,1':3',1″-terphenyl]-4,4″,5'-tricarboxylic acid (H(3)L) and 1,4-diazabicyclo[2.2.2]octane (DABCO). As revealed by variable-temperature powder X-ray diffraction (VT-PXRD) measurements, N,N'-ditopic DABCO plays an important role for stabilization of the Cu-L framework. The three-dimensional framework of 1 exhibits high stability and excellent adsorption capacity for H(2) (54.3 mg g(-1) at 77 K and 20 bar), CO(2) (871 mg g(-1) at 298 K and 20 bar), CH(4) (116.7 mg g(-1), 99 cm(3) (STP) cm(-3) at 298 K and 20 bar), and n-pentane (686 mg g(-1) at 298 K and 1 bar). Interestingly, the excellent selectivity toward CO(2) over N(2) at ambient temperature (273 and 298 K) and 1 bar makes complex 1 possess practical application in gas separation and purification.

Controllable synthesis of a non-interpenetrating microporous metal–organic framework based on octahedral cage-like building units for highly efficient reversible adsorption of iodine

A novel non-interpenetrating metal-organic framework IFMC-15 was successfully constructed based on octahedral cage-like building units and its outstanding performance in reversible adsorption of iodine was investigated.

Selective CO2 adsorption in a flexible non-interpenetrated metal–organic framework

We have prepared a flexible metal-organic framework and demonstrated that when activated by supercritical CO(2) it has greater gas sorption capacities than that activated by the heat-evacuation method, and it selectively adsorbs CO(2) over N(2) at room temperature.

Elucidating steric effects on enantioselective epoxidation catalyzed by (salen)Mn in metal-organic frameworks

The steric effects of a metal-organic framework (MOF) on the enantioselectivity of a (salen)Mn were studied using classical atomistic modeling. Rotational energy profiles for the approach of 2,2-dimethyl-2H-chromene to the active site of (salen)Mn were mapped for the homogeneous catalyst and the catalyst immobilized as a linker in a MOF. The model corroborated that the Re enantioface is favored by the homogeneous catalyst. It was shown that the predicted enantioselectivity when chromene approaches the more accessible (salen)Mn in the MOF is highly sensitive to the distance between the (salen)Mn linkers of the interpenetrated frameworks. Calculated rotational energy profiles for a hypothetical non-interpenetrated MOF revealed that this MOF catalyst should exhibit enantioselectivity intermediate to the interpenetrated MOF and the homogeneous catalyst. Finally, the continuous chirality measure of the catalyst was found to correlate well with the energy of the homogeneous catalyst–reactant complex, suggesting that high chirality content is related to high enantioselectivity. This correlation, however, did not apply for some of the MOF catalysts. For heterogeneous catalysts, the mechanism of asymmetric induction depends on the steric environment in addition to the chirality of the catalyst.