Robust acid-base Ln-MOFs: searching for efficient catalysts in cycloaddition of CO2 with epoxides and cascade deacetalization-Knoevenagel reactions

A family of microporous and robust Ln(iii)-based metal-organic frameworks (1-Ln, Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) have been obtained using 4,4',4''-nitrilotribenzoic acid (H₃NTB) in NMP-HCl solvent. Both single-crystal and powder X-ray diffraction analyses demonstrate that 1-Ln are isostructural and possess 3D frameworks with permanent porosity for Ar and CO₂ adsorption. Strikingly, the incorporation of both Lewis acidic lanthanide ions and the basic triphenylamine group into 1-Ln makes them efficient acid-base catalysts for both cycloaddition of epoxides with CO₂ and one-pot cascade deacetalization-Knoevenagel reactions. The systematic catalytic studies show that 1-Tb and 1-Yb possess the best catalytic activities for both reactions, indicating the catalytic activities of these Ln-MOFs are strongly dependent on metal Lewis acid sites embedded in the frameworks.

Metal-Organic Frameworks for Highly Selective Separation of Xylene Isomers and Single-Crystal X-ray Study of Aromatic Guest-Host Inclusion Compounds

Separation of hydrocarbon molecules, such as benzene/cyclohexane and o-xylene/m-xylene/p-xylene, is relevant due to their widespread application as chemical feedstock but challenging because of their similar boiling points and close molecular sizes. Physisorption separation could offer an energy-efficient solution to this problem, but the design and synthesis of sorbents that exhibit high selectivity for one of the hydrocarbons remain a largely unmet challenge. Herein, we report a new heterometallic MOF with a unique tortuous shape of channels decorated with aromatic sorption sites [Li₂Zn₂(bpy)(ndc)₃] (NIIC-30(Ph), bpy = 4,4'-bipyridine, ndc^2- = naphthalene-1,4-dicarboxylate) and study of its benzene/cyclohexane and xylene vapor and liquid separation. For an equimolar benzene/cyclohexane mixture, it is possible to achieve a 10-fold excess of benzene in the adsorbed phase. In the case of xylenes, microporous framework NIIC-30(Ph) demonstrates outstanding selective sorption properties and becomes a new benchmark for m-/o-xylene separation. In addition, NIIC-30(Ph) is stable enough to carry out at least three separation cycles of benzene/cyclohexane mixtures or ternary o-xylene/m-xylene/p-xylene mixtures both in the liquid and in the vapor phase. Insights into the performance of NIIC-30(Ph) are gained from X-ray structural studies of each aromatic guest inclusion compound.

Two isomeric zeolite-like metal–organic frameworks with mechanically responsive luminescence emission and gas adsorption properties

The two isomeric zeolite-like metal–organic frameworks based on tetrahedral TPO3− ligands and tetrahedrally connected Cd2+ ions were prepared. One of the compounds shows mechanic-responsive luminescence after the crystals were ground for different time.

Boronate Covalent and Hybrid Organic Frameworks Featuring PIII and P=O Lewis Base Sites

Two covalent organic frameworks comprising Lewis basic PIII centers and Lewis acidic boron atoms were prepared by poly-condensation reactions of newly obtained tris(4-diisopropoxyborylphenyl)phosphine with 2,3,6,7,10,11-hexahydroxytriphenylene and 2,3,6,7-tetrahydroxy-9,10-dimethylanthracene. Obtained materials exhibit significant sorption of dihydrogen (100 cm3  g-1 at 1 bar at 77 K), methane (20 cm3  g-1 at 1 bar at 273 K) and carbon dioxide (50 cm3  g-1 at 1 bar at 273 K). They were exploited as solid-state ligands for coordination of Pd0 centers. Alternatively, in a bottom-up approach, boronated phosphine was treated with Pd2 dba3 and poly-condensated, yielding hybrid materials where the polymer networks are formed by means of covalent boronate linkages and coordination P-Pd bonds. In addition, the analogous materials based on phosphine oxide were synthesized. The DFT calculations on framework-guest interactions revealed that the behavior of adjacent boron and phosphorus/phosphine oxide centers is reminiscent of that found in Frustrated Lewis Pairs and may improve sorption of selected molecules.

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.

The crystal structure of diaqua-bis(μ2-3-((3-acetyl-5-carboxyphenyl)oxidophosphoryl)-5-carboxybenzoato-κ2 O:O′)bis(5,5′-dimethyl-2,2′-bipyridine-k2 N,N′)zinc(II), C56H46N4O22P2Zn2

C56H46N4O22P2Zn2, monoclinic, P21/c (no. 14), a = 9.6537(4) Å, b = 31.1374(11) Å, c = 9.8927(4) Å, β = 112.709(2)°, V = 2743.13(19) Å3, Z = 2, R gt(F) = 0.0341, wR ref(F 2) = 0.0934, T = 296(2) K.

A new set of metal–organic frameworks synthesised from diisophthalate-based, 2′-phosphorus-substituted m-terphenyl linker molecules

Four metal–organic frameworks employing the m-terphenyl diisophthalate linker molecule with 2′ substitution by P(v)-based functional groups of the central aryl have been synthesised.

Water-Stable Anionic Metal-Organic Framework for Highly Selective Separation of Methane from Natural Gas and Pyrolysis Gas

A 3D water-stable anionic metal-organic framework [Zn4(hpdia)2]·[NH2(CH3)2]·3DMF·4H2O (FJI-C4) was constructed based on an elaborate phosphorus-containing ligand 5,5'-(hydroxyphosphoryl)diisophthalic acid (H5hpdia). FJI-C4 with narrow one-dimensional (1D) pore channels exhibits high selectivity of C3H8/CH4 and C2H2/CH4. It is the first time for the MOF which contains phosphorus for selective separation of methane from natural gas and pyrolysis gas.

A porous magnesium metal–organic framework showing selective adsorption and separation of nitrile guest molecules

Selective and reversible adsorption of nitrile guest molecules including MeCN, ACN, AN and CTN on a Mg-based MOF were reported. Interestingly, the Mg-based MOF selectively captured cis-CTN into its cavity from a mixture of cis- and trans-isomers.

CO2 capture in the presence of water vapour in MIL-53(Al)

By kinetic uptake experiments, MIL-53(Al) shows under anhydrous conditions at 30 °C a CO₂ capture of 3.5 wt%. When this material is exposed to water vapour (20% RH and 30 °C), there is a considerable 1.5-fold increase in the CO₂ capture up to 5.2 wt%.

Removal of CO2from CH4and CO2capture in the presence of H2O vapour in NOTT-401

NOTT-401 shows a significant 7-fold increase (∼9.90 wt%) in CO₂capture under 40% relative humidity.

Separation of CO2from CH4and CO2capture in the presence of water vapour in NOTT-400

NOTTS-400 exhibits CO₂separation from CH₄when the material was exposed to a binary (CO₂/CH₄) equimolar gas-mixture and this was confirmed byin situFTIR spectroscopy.

An ionothermally synthesized Mg-based coordination polymer as a precursor for preparing porous carbons

An ionothermally synthesized Mg-CP has been utilized as the first Mg-based precursor for preparing porous carbons through thermal decomposition.

A two-dimensional flexible porous coordination polymer based on Co(ii) and terpyridyl phosphine oxide

A 2D framework with –P(O)Ph₂ phenyl groups on the layer surface has been obtained, which shows remarkable dynamic sorption behaviours.

Carbon dioxide capture in the presence of water vapour in InOF-1

InOF-1 confirms a significant 2-fold increase (∼11 wt%) in CO₂ capture under 20% relative humidity of water vapour.

Coordination polymers constructed from a tripodal phosphoryl carboxylate ligand: synthesis, structures and physical properties

Four coordination polymers based on a new tripodal phosphoryl carboxylate H₃TBPPO ligand have been constructed and characterized. Complexes 1–3 show 2-fold interpenetrating flu net, while complex 4 possesses a 4-fold interpenetrating dia network.

Microwave-assisted synthesis of a series of lanthanide metal-organic frameworks and gas sorption properties

A series of isostructural microporous lanthanide metal-organic frameworks (MOFs) formulated as [Ln(2)(TPO)(2)(HCOO)]·(Me(2)NH(2))·(DMF)(4)·(H(2)O)(6) {Ln = Y (1), Sm (2), Eu (3), Gd (4), Tb (5), Dy (6), Ho (7), Er (8), Tm (9), Yb (10), and Lu (11); H(3)TPO = tris-(4-carboxylphenyl)phosphineoxide; DMF = N,N-dimethylformamide} has been synthesized under microwave-assisted solvothermal reaction for 30 min. Alternatively, if a conventional solvothermal reaction is carried out under the same temperature, a much longer time (3 days) is needed for the same phase in similar yield. Structure analysis reveals that the framework is a 4,8-connected network with point symbol (4(10)·6(16)·8(2)) (4(5)·6)(2), which is the subnet of alb net. Thermal gravimetric analyses performed on as-synthesized MOFs reveal that the frameworks have high thermal stability. The luminescent properties of 2, 3, 5, and 6 were investigated and show characteristic emissions for Sm(III), Eu(III), Tb(III), and Dy(III) at room temperature, respectively. Gas sorption properties of 1 and 3 were studied by experimentally measuring nitrogen, argon, carbon dioxide, methane, and hydrogen sorption isotherms. The resulting materials show high and preferential CO(2) adsorption over N(2) gas at ambient temperature, indicating that the present materials can be applied in a CO(2) capture process.