Connected Metal Organic Framework Research Articles

An isostructural series of metal-organic frameworks: selective gas adsorption and sensing studies

The solvothermal reaction of Ln(NO3)3•6H2O (Ln = Nd, Sm, Eu, Tb, and Dy) with 9,10-bis(4-carboxylatopyridinium-1-methylene)anthracene dibromide (H2L)Br2 resulted in the formation of an isostructural series of lanthanide-based metal organic frameworks (Ln-MOFs), {[Nd(L)3/2(H2O)2]·(NO3)3·(S)}n (1), {[Sm(L)3/2(H2O)2]·(NO3)3·(S)}n (2), {[Eu(L)3/2(H2O)2]·(NO3)3·(S)}n (3), {[Tb(L)3/2(H2O)2]·(NO3)3·(S)}n (4) and {[Dy(L)3/2(H2O)2]·(NO3)3·(S)}n (5), where S denotes squeezed disordered solvent molecules and out of three nitrate ions in the voids, one nitrate is squeezed due to the high disorder. These MOFs were characterized with various techniques and single crystal X-ray analysis revealed a three dimensional (3D) (4,4,6)-connected metal organic framework with mononuclear metallic nodes in bicapped trigonal prismatic geometry. From the present series, we selected {[Sm(L)3/2(H2O)2]·(NO3)3·(S)}n (2) as a representative example for structural description and gas adsorption study whereas {[Dy(L)3/2(H2O)2]·(NO3)3·(S)}n (5) was used for the sensing of nitro compounds. All MOFs showed stability up to 200 °C. 2 demonstrates a higher CO2 uptake, despite exhibiting a low specific surface area (SABET) in N2 sorption studies. The sensing result shows that 5 act as selective sensors towards TNP with quenching efficiency greater than 99%.

A highly connected metal–organic framework with a specific nonpolar nanotrap for inverse ethane/ethylene separation

A highly connected Tb-MOF possessing a specific nanotrap enriched with nonpolar aromatic rings shows an excellent inverse adsorption of C2H6 over C2H4 for one-step C2H4 purification.

Accessing 14-Connected Nets: Continuous Breathing, Hydrophobic Rare-Earth Metal Organic Frameworks Based on 14-c Hexanuclear Clusters with High Affinity for Non-Polar Vapors.

Highly connected metal organic frameworks (MOFs) in which at least one building block has connectivity higher than twelve are very rare and much desirable. We report here the first examples of isostructural 14-connected MOFs, RE-frt-MOF-1, constructed from the assembly of 14-c hexanuclear rare-earth clusters, [RE6(μ3-X)8(COO)12]2- (RE: Y3+, Tb3+, Dy3+, Ho3+, Er3+, Yb3+ and X: OH-/F-) with a tritopic carboxylate-based organic linker. This linker serves as a 3-c and 4-c organic node resulting in the formation of a unique, trinodal (3,4,14)-c framework. RE-frt-MOF-1 are stable in air and alkaline aqueous solutions and show an intriguingly continuous, reversible breathing behavior, between a wide and a narrow-pore phase, upon guest removal. Crystallinity is retained during breathing, and single-crystal X-ray diffraction shed light into the associated structural transformation. Vapor sorption studies performed on Y-frt-MOF-1 revealed a high affinity for non-polar vapors such as n-hexane, cyclohexane, and benzene, displaying type I isotherms with high uptake at low relative pressures (<10-3 p/p0), associated with the hydrophobic nature of the 1D channels and also with their rhombic shape. In contrast, polar vapors such as acetonitrile and ethanol show type V isotherms due to favorable vapor-vapor interactions. Notably these vapors, except cyclohexane, trigger the transition from the narrow to the wide pore phase, accompanied by a remarkable increase in uptake, reaching 70.6, 109, 100.4, and 87.7% for n-hexane, benzene, acetonitrile, and ethanol, respectively.

Selective Gas Uptake and Rotational Dynamics in a (3,24)-Connected Metal-Organic Framework Material.

The desolvated (3,24)-connected metal-organic framework (MOF) material, MFM-160a, [Cu3(L)(H2O)3] [H6L = 1,3,5-triazine-2,4,6-tris(aminophenyl-4-isophthalic acid)], exhibits excellent high-pressure uptake of CO2 (110 wt% at 20 bar, 298 K) and highly selective separation of C2 hydrocarbons from CH4 at 1 bar pressure. Henry's law selectivities of 79:1 for C2H2:CH4 and 70:1 for C2H4:CH4 at 298 K are observed, consistent with ideal adsorption solution theory (IAST) predictions. Significantly, MFM-160a shows a selectivity of 16:1 for C2H2:CO2. Solid-state 2H NMR spectroscopic studies on partially deuterated MFM-160-d12 confirm an ultra-low barrier (∼2 kJ mol-1) to rotation of the phenyl group in the activated MOF and a rotation rate 5 orders of magnitude slower than usually observed for solid-state materials (1.4 × 106 Hz cf. 1011-1013 Hz). Upon introduction of CO2 or C2H2 into desolvated MFM-160a, this rate of rotation was found to increase with increasing gas pressure, a phenomenon attributed to the weakening of an intramolecular hydrogen bond in the triazine-containing linker upon gas binding. DFT calculations of binding energies and interactions of CO2 and C2H2 around the triazine core are entirely consistent with the 2H NMR spectroscopic observations.

Synthesis of Polycarboxylate Rhodium(II) Metal–Organic Polyhedra (MOPs) and their use as Building Blocks for Highly Connected Metal–Organic Frameworks (MOFs)

AbstractUse of preformed metal‐organic polyhedra (MOPs) as supermolecular building blocks (SBBs) for the synthesis of metal‐organic frameworks (MOFs) remains underexplored due to lack of robust functionalized MOPs. Herein we report the use of polycarboxylate cuboctahedral RhII‐MOPs for constructing highly‐connected MOFs. Cuboctahedral MOPs were functionalized with carboxylic acid groups on their 12 vertices or 24 edges through coordinative or covalent post‐synthetic routes, respectively. We then used each isolated polycarboxylate RhII‐MOP as 12‐c cuboctahedral or 24‐c rhombicuboctahedral SBBs that, upon linkage with metallic secondary building units (SBUs), afford bimetallic highly‐connected MOFs. The assembly of a pre‐synthesized 12‐c SBB with a 4‐c paddle‐wheel SBU, and a 24‐c SBB with a 3‐c triangular CuII SBU gave rise to bimetallic MOFs having ftw (4,12)‐c or rht (3,24)‐c topologies, respectively.

Synthesis of Polycarboxylate Rhodium(II) Metal-Organic Polyhedra (MOPs) and their use as Building Blocks for Highly Connected Metal-Organic Frameworks (MOFs).

Use of preformed metal-organic polyhedra (MOPs) as supermolecular building blocks (SBBs) for the synthesis of metal-organic frameworks (MOFs) remains underexplored due to lack of robust functionalized MOPs. Herein we report the use of polycarboxylate cuboctahedral RhII -MOPs for constructing highly-connected MOFs. Cuboctahedral MOPs were functionalized with carboxylic acid groups on their 12 vertices or 24 edges through coordinative or covalent post-synthetic routes, respectively. We then used each isolated polycarboxylate RhII -MOP as 12-c cuboctahedral or 24-c rhombicuboctahedral SBBs that, upon linkage with metallic secondary building units (SBUs), afford bimetallic highly-connected MOFs. The assembly of a pre-synthesized 12-c SBB with a 4-c paddle-wheel SBU, and a 24-c SBB with a 3-c triangular CuII SBU gave rise to bimetallic MOFs having ftw (4,12)-c or rht (3,24)-c topologies, respectively.

Pore Engineering of Covalently Connected Metal–Organic Framework Nanoparticle–Mixed-Matrix Membrane Composites for Molecular Separation

Fine-tuning and pore environment control of covalently connected metal-organic framework (MOF) and mixed-matrix membrane (MMM) composite materials were achieved. Core-shell-type, dual-functionalize...

A novel enhancement of shape/thermal stability and energy-storage capacity of phase change materials through the formation of composites with 3D porous (3,6)-connected metal–organic framework

Leakage at temperatures above the melting point and thermal-transport performance are prime factors for the effective application of phase change materials (PCMs). In this study, a shape-stabilized composite PCM based on a three-dimensional (3D) porous (3,6)-connected metal–organic framework (MOF) and polyethylene glycol (PEG) was designed. The (3,6)-connected Zn2+ MOF gel was used as a porous supporting material, whereas PEG was employed as an energy-storage material. The PCM, which was impregnated by a capillary force and anchored by a weak hydrogen-bonding interaction between hydroxyl and amine groups, was stabilized by the supporting material. The 3D and two-fold interpenetrated structure of the MOF provided continuous heat-transfer paths in the composite PCM. The resulting composite material exhibited a high transition enthalpy (159.8 kJ/kg) with an encapsulation efficiency and impregnation ratio of 93.4% and 92.2%, respectively. The large interior surface accessibility of the MOF played a vital role in enhancing the thermal properties of the as-synthesized composite PCM. Additionally, the composite PCM exhibited excellent thermal stability and reliability even after 100 thermal cycles. Therefore, the composite PCM is a promising candidate for thermal-energy management systems owing to its high latent heat, suitable phase-change temperature, good chemical compatibility, reduced extent of supercooling, and high thermal stability.

Molecular Pivot‐Hinge Installation to Evolve Topology in Rare‐Earth Metal–Organic Frameworks

AbstractLinker desymmetrization has been witnessed as a powerful design strategy for the discovery of highly connected metal–organic frameworks (MOFs) with unprecedented topologies. Herein, we introduce molecular pivot‐hinge installation as a linker desymmetrization strategy to evolve the topology of highly connected rare‐earth (RE) MOFs, where a pivot group is placed in the center of a linker similar to a hinge. By tuning the composition of pivot groups and steric hindrances of the substituents on various linker rotamers, MOFs with various topologies can be obtained. The combination of L‐SO2 with C2v symmetry and 12‐connected RE9 clusters leads to the formation of a fascinating (4,12)‐c dfs new topology. Interestingly, when replacing L‐SO2 with a tetrahedra linker L‐O, the stacking behaviors of RE‐organic layers switch from an eclipsed mode to a staggered stacking mode, leading to the discovery of an intriguing hjz topology. Additionally, the combination of the RE cluster and a linker [(L‐(CH3)6)] with more bulky groups gives rise to a flu topology with a new 8‐c inorganic cluster. The diversity of these RE‐MOFs was further enhanced through post‐synthetic installation of linkers with various functional groups. Functionalization of each linker with acidic and basic units in the mesoporous RE‐based PCN‐905‐SO2 allows for efficient cascade catalytic transformation within the functionalized channels.

Extraordinary cycling stability of Ni3(HITP)2 supercapacitors fabricated by electrophoretic deposition: Cycling at 100,000 cycles

Two-dimensionally (2D) connected metal organic frameworks (MOFs) are a new class of materials that are of considerable interest because of their potential applications in energy storage devices. In this work we report, the fabrication, by electrophoretic deposition (EPD) of, an ultra-high cycling stability supercapacitor, with the 2D MOF Nickel-2,3,6,7,10,11-hexaaminotriphenylene (Ni3(HITP)2) as the active electrode material. The MOF-based symmetric supercapacitor, exhibited an excellent electrochemical capacitive performance over a potential window of 0–1.0 V, and displayed an areal specific capacitance of 15.69 mF cm−2. Furthermore, the Ni3(HITP)2 supercapacitor exhibited an exceptional capacitance retention of 84% after 100,000 cycles providing the best reported ultra-high cycling stability for an MOF to date. Such excellent electrochemical performance is attributed to the EPD process, the 2D MOFs nanosheets which facilitate the electron transfer and electrolyte diffusion, and the large surface area of Ni3(HITP)2. These results provide a great prospect for developing MOFs as a new class of materials for energy storage devices.

Unique self-catenated 3D Cd(II)-MOF with a rare (3,3,9)-connected underlying network exhibiting high photocatalytic activities

An unprecedented 3D self-catenated topology with highly connected metal–organic framework, [Cd3(nbta)1.5(btb)2(H2O)]n (1) (H3nbta = 5-nitro-1,2,3-benzenetricarboxylic acid, btb = 4,4′-bis(1,2,4-triazol-1-yl)-biphenyl) on the basis of Cd3 clusters was hydrothermally synthesized and characterized. Compound 1 possesses a unique (3,3,9)-coordinated framework, in which the nbta3− ligands serve as two unusual pentadentate and heptadentate coordination modes. Compound 1 exhibits highly photocatalytic activities for the degradation of MB/MO/RhB organic dyes.

An uncommon 3D Co5-cluster-based metal-organic framework: Synthesis, structure and magnetism

A highly connected metal–organic framework (MOF), namely, [Co5(μ3-OH)2(iapt)4(4,4′-bipy)0.5(H2O)·CH3CN·3H2O] (1) (H2iapt=5-aminoisophthalic acid and 4,4′-bipy=4,4′-bipyridine), is reported. 1 shows a complicated pentanodal 4,4,4,4,13-c 3D net with (43)(43)(43)(43)(420·514·623·78·813) topology based on an uncommon Co5 cluster. The magnetic analysis reveals antiferromagnetic interactions in 1, and both the local spin–orbit coupling of octahedral Co(II) ions and the antiferromagnetic interactions are the primary factors in the magnetic behaviour.

A noncovalently connected metal–organic framework assembled from a Ni(iii)-supported polyoxometalate–imidazolate hybrid

The first mixed-valence nickel-supported polyoxometalate-based metal–organic framework, (H2mim)[NiIII(Hmim)4][SiW11NiIIO37(OH)2(Hmim)]·3H2O (1) (Hmim = 2-methylimidazole), has been synthesized using a steam-assisted conversion method, and is constructed from noncovalent interactions (hydrogen bonds and π⋯π stacking interactions). 1 has a repeating honeycomb-shaped internal structure with one-dimensional channels along the direction of the c axis, where the diameter of the aperture is as large as 18.83 A. Furthermore, the stability and the optical band gaps are investigated.

A (3,6)-Connected Metal–Organic Framework with pyr Topology and Highly Selective CO2 Adsorption

Upon the basis of a bifunctional organic ligand with two carboxyl groups and one N donor, 5-(quinolin-4-yl)isophthalic acid (H2L), a new (3,6)-connected metal–organic framework with pyr topology, [Cu(L)·DMF]n (NJU-Bai32), has been synthesized and exhibits highly selective CO2 adsorption.

Metal nuclearity affects network connectivity: a series of highly connected metal–organic frameworks based on polynuclear metal clusters as secondary building units

Seven novel highly connected metal–organic frameworks (MOFs), formulated as [Co7(aobtc)3(bpy)2(μ3-OH)2(μ2-OH2)2(H2O)4]·4H2O (1), [Ni5(aobtc)2(bpy)2(μ3-OH)2(H2O)6]·4H2O (2), [Zn3(aobtc)2]·H2bpy·H2O (3), [Zn3(aobtc)2]·H2bpp·H2O (4), [Cd3(aobtc)2]·[Me2NH2]2·3H2O (5), [Co3(aobtc)2]·H2bpp·H2O (6) and [Mn3(aobtc)2]·H2bpy·2H2O (7) (H4aobtc = azoxybenzene-3,3′,5,5′-tetracarboxylic acid, bpy = 4,4′-bipyridine, bpp = 1,3-bis(4-pyridyl)propane) have been synthesized and characterized by elemental analyses, IR spectra, single-crystal X-ray diffraction, powder X-ray diffraction, and thermal analyses. Compound 1 is a 3D (4,4,14)-connected self-penetrating framework with (46)2(45·6)(430·526·631·74) topology based on hexanuclear clusters as 14-connected nodes. To our knowledge, compound 1 represents the highest connected self-penetrating topology presently known in the entangled system. Compound 2 displays a trinodal (4,4,10)-connected network with (46)(45·5)(410·518·612·75) topology based on tetranuclear clusters as 10-connected nodes. Compounds 3–7 exhibit (4,8)-connected flu nets based on trinuclear clusters as 8-connected nodes, and these five MOFs show similar structures but different pore volumes mainly associated with the change of the species of guest molecules. Structural analyses of 1–7 demonstrate that increasing the metal nuclearity is a practical method to obtain highly connected coordination networks based on metal clusters as nodes. In addition, the magnetic properties of 1, 2, 6, and 7 and the luminescence properties of compounds 3–5 have also been studied.

A (3,6)-connected metal–organic framework with high CH4binding affinity and uptake capacity

A (3,6)-connected metal–organic framework with a fit-3 topology, [CuL(NO3)]·2DMF·H2O (NJU-Bai16), has been synthesized by self-assembly of binuclear [Cu2(COO)2N4] building blocks and heterofunctional ligand 3,5-di(pyridin-4-yl) benzoic acid (HL). The small pores within the framework have enabled their strong interactions with CH4 molecules. NJU-Bai16 was thereby found to exhibit high isosteric heats of CH4 adsorption (23.3 kJ mol−1) and uptake capacity (50.3 cm3 g−1 at 1 bar and 273 K). Additionally, NJU-Bai16 demonstrates high CO2 uptake (22.4 wt% at 1 bar) with excellent selectivity for CO2 over N2 (29.7) at 273 K.

Isoreticular Series of (3,24)-Connected Metal–Organic Frameworks: Facile Synthesis and High Methane Uptake Properties

We have successfully used a highly efficient copper-catalyzed “click” reaction for the synthesis of a new series of hexacarboxylic acid linkers with varying sizes for the construction of isoreticular (3,24)-connected metal–organic frameworks (MOFs)—namely, NU-138, NU-139, and NU-140. One of these MOFs, NU-140, exhibits a gravimetric methane uptake of 0.34 g/g at 65 bar and 298 K, corresponding to almost 70% of the DOE target (0.5 g/g), and has a working capacity (deliverable amount between 65 and 5 bar) of 0.29 g/g, which translates into a volumetric working capacity of 170 cc(STP)/cc. These values demonstrate that NU-140 performs well for methane storage purposes, from both a gravimetric and a volumetric point of view. Adsorption of CO2 and H2 along with simulated isotherms are also reported.

Spontaneous chiral resolution of a 3D (3,12)-connected MOF with an unprecedented ttt topology consisting of cubic [Cd4(μ3-OH)4] clusters and propeller-like ligands

The enantiomers of complex 1 (1Δ and 1Λ), [Cd(tipa)(μ3-OH)·NO3·EtOH·DMF]n (tipa = tris(4-(1H-imidazol-1-yl)phenyl)amine), have been obtained by spontaneous resolution upon crystallization in the absence of any enantiopure substance. Complex 1 shows an unprecedented 3D (3,12)-connected metal–organic framework with ttt topology consisting of cubic [Cd4(μ3-OH)4] clusters and propeller-like ligands. The anion-exchange and iodine uptake behaviors of 1 are investigated.

A rare (3,4,5)-connected metal-organic framework featuring an unprecedented 1D + 2D → 3D self-interpenetrated array and an O-atom lined pore surface: structure and controlled drug release.

A rare (3,4,5)-connected self-interpenetrated metal-organic framework with an O-atom lined pore surface has been constructed from Zn(II) and H4L (H4L = 5,5'-(1,3,6,8-tetraoxobenzo[lmn][3,8]phenanthroline-2,7(1H,3H,6H,8H)diyl)-diisophthalic acid), which features an unprecedented 1D + 2D → 3D self-interpenetrated array and shows good controlled drug release properties.

An unprecedented binodal (4,10)-connected metal–organic framework based on pentanuclear cobalt(II) clusters

A three-dimensional Co(II) metal–organic framework {[Co5(btec)2(btx)(μ3-OH)2(H2O)2]·2H2O}n (1) (H4btec=1,2,4,5-benzenetetracarboxylic acid, btx=1,4-bis(1,2,4-triazol-1-ylmethyl)benzene) containing rare pentanuclear Co(II)-clusters has been hydrothermally synthesized and structurally characterized, and shows an unusual binodal (4,10)-connected topology. The fluorescence properties and catalytic activity of the complex for degradation of methyl orange in the Fenton-like process were investigated.