An Interpenetrated Metal–Organic Framework and Its Gas Storage Behavior: Simulation and Experiment

A 2D coordination polymer assembled from a nickel(II) tetraazamacrocyclic cation and 4,4'-(dimethylsilanediyl)diphthalate(3-) linker

The preformed nickel(II) complex of the 14-membered macrocyclic ligand 1,4,8,11-tetraazacyclotetradecane (cyclam, L), when treated with 4,4'-(dimethylsilanediyl)diphthalic acid (H₄A) in a DMF/H₂O mixture (4:1 v/v) under heating, leads to [Ni(L)]₃(HA)₂·3DMF (I·DMF). Redissolution of this compound in a DMF/H₂O/MeOH mixture (4:1:30 v/v/v) with mild acidification under gentle heating results in the formation of a similar compound but containing water and methanol molecules of crystallization, [Ni(L)]₃(HA)₂·5H₂O·2MeOH (II·H₂O). At lower temperature and concentration of reactants and longer reaction time, single crystals of composition {[{Ni(L)}₃(HA)₂]·4CH₃OH}_n (II·MeOH) were isolated. Single-crystal X-ray diffraction analysis of this compound, which, according to PXRD is isostructural with II·H₂O but different from I·DMF, revealed its two-dimensional (2D) polymeric structure, i.e. poly[[bis{μ₃-4-[(4-carboxy-3-carboxylatophenyl)dimethylsilyl]benzene-1,2-dicarboxylato-κ³O¹:O²:O^3'}tris(1,4,8,11-tetraazacyclotetradecane-κ⁴N)trinickel(II)] methanol tetrasolvate], {[Ni₃(C₁₈H₁₃O₈Si)₂(C₁₀H₂₄N₄)₃]·4CH₃OH}_n. It is built up of the monoprotonated tricarboxylate HA^3- ligand coordinated in a monodentate manner in the axial positions of two crystallographically independent Ni^II cations, one of which is located on a crystallographic inversion centre. Both metal ions adopt a slightly tetragonally elongated trans-N₄O₂ octahedral geometry. The compound has a lamellar structure with polymeric layers oriented parallel to the (10-2) plane, which are in turn linked via hydrogen bonds involving protonated carboxylic acid groups of the ligand. Bulk compounds I·DMF and II·H₂O were characterized by FT-IR and diffuse reflectance spectroscopy and thermogravimetry, which provide evidence of their structural differences.

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.

Effect of arrangement of functional groups on stability and gas adsorption properties in two regioisomeric copper bent diisophthalate frameworks

The substituent's arrangement was found to have a significant effect on the structural stabilities and thus gas adsorption properties of the resultant MOFs.

Tailoring the structures and gas adsorption properties of copper–bent diisophthalate frameworks by a substituent-driven ligand conformation regulation strategy

A substituent-induced ligand conformation regulation strategy was employed to tailor the structures and gas adsorption properties of copper-bent diisophthalate frameworks.

A metal-organic framework based on a custom-designed diisophthalate ligand exhibiting excellent hydrostability and highly selective adsorption of C2H2 and CO2 over CH4

The ligand truncation strategy provides facile access to a wide variety of linkers for the construction of MOFs bearing diverse structures and intriguing properties. In this work, we employed this strategy to design and prepare a novel bent diisophthalate ligand, and used it to successfully construct a copper-based MOF ZJNU-51 with the formula of [Cu2L(H2O)2]·5DMF (H4L = 5,5'-(triphenylamine-4,4'-diyl) diisophthalic acid), which was thoroughly characterized by various techniques including FTIR, TGA, PXRD and single-crystal X-ray diffraction. ZJNU-51 is a two-fold interpenetrated network in which the single network consists of dicopper paddlewheel units connected by the organic ligands and contains open channels as well as six distinct types of metal-organic cages. Furthermore, gas adsorption properties with respect to C2H2, CO2, and CH4 were systematically investigated, demonstrating that ZJNU-51 is a highly promising material for C2H2/CH4 and CO2/CH4 separations. Specifically, the IAST adsorption selectivity at 298 K and 1 atm reaches 35.6 and 5.4 for the equimolar C2H2/CH4 and CO2/CH4 gas mixtures, respectively. More significantly, as revealed by PXRD and N2 adsorption measurements, ZJNU-51 exhibits excellent chemical stability, which lays a good foundation for its practical application.

Three isoreticular ssa-type MOFs derived from bent diisophthalate ligands: exploring the substituent effect on structural stabilities and selective C2H2/CH4 and CO2/CH4 adsorption properties

Three isoreticular ssa-type MOFs exhibit substituent-dependent framework stabilities against desolvation and gas adsorption properties.

Three isoreticular MOFs derived from nitrogen-functionalized diisophthalate ligands: exploring the positional effect of nitrogen functional sites on the structural stabilities and selective C2H2/CH4 and CO2/CH4 adsorption properties

The positional effect of nitrogen functional sites on the structural stability and gas adsorption property was explored in a family of ssa-type MOFs.

Rational construction of an ssa-type of MOF through pre-organizing the ligand's conformation and its exceptional gas adsorption properties

A ligand conformation-controlled assembly strategy has been successfully employed to construct a copper-based MOF with the desired ssa-type topology, which exhibits exceptional C₂H₂ and CO₂ adsorption properties.

A pair of polymorphous metal–organic frameworks based on an angular diisophthalate linker: synthesis, characterization and gas adsorption properties

A pair of polymorphous MOFs derived from a bent diisophthalate ligand were synthesized by modulating solvothermal conditions, exhibiting comparable gas adsorption properties with respect to C₂H₂, CO₂ and CH₄.

Three ligand-originated MOF isomers: the positional effect of the methyl group on structures and selective C2H2/CH4 and CO2/CH4 adsorption properties

The positional effect of the methyl group on structures and gas adsorption properties was explored in a copper-based MOF platform constructed from bent diisophthalate ligands bearing the methyl group at different positions.

A porous metal–organic framework based on an asymmetric angular diisophthalate for selective adsorption of C2H2 and CO2 over CH4

A porous MOF based on an amine-functionalized asymmetric bent diisophthalate was synthesized that exhibits impressive selective adsorption of C₂H₂ and CO₂ over CH₄ under ambient conditions.

Screening of hypothetical metal-organic frameworks for H2 storage

Computational screening throughout a database containing ∼138 000 metal-organic frameworks (MOFs) has been performed to select candidate structures for hydrogen storage. A total of 231 structures (of which 79 contain paddle-wheel units) have been selected that meet the gravimetric and volumetric targets at 100 atm and 77 K. Grand Canonical Monte Carlo simulations have been performed to calculate the isotherms and select structures which meet the targets at 50 atm, and also to check the adsorption in the low pressure regime (1 atm). From this a reduced set of 18 structures has been analysed in more detail, regarding not only gravimetric and volumetric uptake but also pore size distribution and pore volume. A few structures with 3% gravimetric uptake at 1 atm and 77 K perform at the best level found so far.

Reversible single-crystal-to-single-crystal transformation from a mononuclear complex to a fourfold interpenetrated MOF with selective adsorption of CO2

Reversible crystal transformation was observed between a mononuclear complex to a fourfold interpenetrated MOF with selective adsorption of CO₂ up to 12.5 wt% at room temperature and low pressure.

Revealing the structure–property relationship of covalent organic frameworks for CO2 capture from postcombustion gas: a multi-scale computational study

Formation of slit-like pores with suitable size by structural realignment of 2D-COFs will greatly enhance their CO₂ capture capability.