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Sulfonated graphitic carbon nitride having both Brønsted base and Brønsted acid sites is used as a heterogeneous catalyst for the selective conversion of different biomass-derived saccharides to 5-hydroxymethylfurfural in green solvents.

Highly thermal and chemically stable, 20-connected lanthanide metal–organic frameworks (MOFs) [{Ln­(BTB)­(H2O)}­·H2O] n (where Ln = Sm (MOF1)/Gd (MOF2), BTB = 1,3,5-tris (4-carboxy phenyl) benzene) have been synthesized solvothermally and characterized by single-crystal X-ray diffraction analysis and other physicochemical methods. MOF1 and 2 are isostructural and feature three-dimensional honeycomb-like structure with large one-dimensional hexagonal channels of dimension ∼10.20 × 10.11 Å2. Gas uptake studies of the samples revealed selective adsorption properties of MOF1 for CO2 over other (N2, Ar, and H2) gases. The activated samples of the MOF1/2 act as efficient recyclable catalysts for heterogeneous cycloaddition of CO2 with styrene oxide, resulting in cyclic carbonate with high yield and selectivity. Interestingly, the pore size-dependent catalytic conversion of epoxides has been observed, suggesting the potential utility of MOF1 as a promising heterogeneous catalyst for cycloaddition of carbon dioxide. Furthermore, the MOF1 catalyst can be easily recycled for several cycles without significant loss of catalytic activity as well as structural rigidity. MOF1 and 2 represent rare examples of 20-c lanthanide MOFs exhibiting selective capture and efficient cycloaddition of CO2 with epoxides at mild conditions.

Non-steroidal anti-inflammatory drugs (NSAIDs) are a group of molecules which have been found to be active against cancer cells with chemopreventive properties by targeting cyclooxygenase (COX-1 and COX-2) and lipoxygenase (LOX), commonly upregulated (particularly COX-2) in malignant tumors. Arene ruthenium(ii) complexes with a pseudo-octahedral coordination environment containing different ancillary ligands have shown remarkable activity against primary and metastatic tumors as reported earlier. This work describes the synthesis of four novel ruthenium(ii)-arene complexes viz. [Ru(η-p-cymene)(nap)Cl] 1 [Hnap = naproxen or (S)-2-(6-methoxy-2-naphthyl)propionic acid], [Ru(η-p-cymene)(diclo)Cl] 2 [Hdiclo = diclofenac or 2-[(2,6-dichlorophenyl)amino] benzeneacetic acid, [Ru(η-p-cymene)(ibu)Cl] 3 [Hibu = ibuprofen or 2-(4-isobutylphenyl)propanoic acid] and [Ru(η-p-cymene)(asp)Cl] 4 [Hasp = aspirin or 2-acetoxy benzoic acid] using different NSAIDs as chelating ligands. Complexes 1-3 have shown promising antiproliferative activity against three different cell lines with GI (concentration of drug causing 50% inhibition of cell growth) values comparable to adriamycin. At the concentration of 50 μM, complex 3 is more effective in the inhibition of cyclooxygenase and lipooxygenase enzymes, followed by complex 2 and complex 1 in comparison to their respective free NSAID ligands indicating a possible correlation between the inhibition of COX and/or LOX and anticancer properties. Molecular docking studies with COX-2 reveal that complexes 1 and 2 having naproxen and diclofenac ligands exhibit stronger interactions with COX-2 than their respective free NSAIDs and these results are in good agreement with their relative experimentally observed COX inhibition as well as anti-proliferative activities.

Sustainable hydrogen transfer reactions without the use of expensive noble metals and toxic solvents is a challenging task. In this work, a process has been developed for selective hydrogenation of carbonyl compounds to corresponding alcohols.

A series of three new isostructural metal-organic frameworks (MOFs) of nickel(II), [{Ni(muco)(bpa)(2HO)}·2HO] (1), [{Ni(muco)(bpe)(2HO)}·2.5HO] (2), and [{Ni(muco)(azopy)(2HO)}·2HO] (3) [where muco = trans,trans-muconate dianion, bpa = 1,2-bis(4-pyridyl)ethane, bpe = 1,2-bis(4-pyridyl)ethylene, and azopy = 4,4'-bis(azobipyridine)], have been synthesized and characterized by single-crystal X-ray diffraction analysis and other physicochemical methods. Compounds 1-3 exhibit an interesting 3-fold-interpenetrated three-dimensional pillar-layered framework structure constituted of 4-coordinating (4-c) Ni nodes with {6}-neb net topology. Remarkably, in spite of 3-fold interpenetration, the structures possess one-dimensional channels with dimensions of ∼8.05 × 5.25 Å. Gas (N, Ar, H, and CO) adsorption studies of compounds 2 and 3 revealed selective adsorption properties for CO over other gases. In all three structures, the 4-c Ni node has two coordinated HO molecules that can be reversibly removed by high-temperature treatment to generate a dehydrated framework composed of highly unsaturated, Lewis acidic Ni ions. Further, the activated compounds of 1-3 act as efficient recyclable catalysts for heterogeneous cycloaddition of CO with styrene oxide, resulting in cyclic carbonate with high conversion and selectivity. Interestingly, the cycloaddition reactions of CO with bulky epoxides show a decrease in the activity with an increase in the alkyl chain length of the substrate due to confinement of the pore size of the MOF. The high catalytic efficiency and size-dependent selectivity for smaller epoxides show the potential utility of 1 as a promising heterogeneous catalyst for the cycloaddition of CO. Furthermore, the catalyst can be easily separated and reused for several cycles without significant reduction in the catalytic activity as well as structural rigidity. Compounds 1-3 represent rare examples of interpenetrated MOFs exhibiting selective storage and conversion of CO at mild conditions.

The concentration of carbon dioxide (CO2) in the atmosphere is increasing at an alarming rate resulting in undesirable environmental issues. To mitigate this growing concentration of CO2, selective carbon capture and storage/sequestration (CCS) are being investigated intensively. However, CCS technology is considered as an expensive and energy‐intensive process. In this context, selective carbon capture and utilization (CCU) as a C1 feedstock to synthesize value‐added chemicals and fuels is a promising step towards lowering the concentration of the atmospheric CO2 and for the production of high‐value chemicals. Towards this direction, several strategies have been developed to convert CO2, a Greenhouse gas (GHG) into useful chemicals by forming C−N, C−O, C−C, and C−H bonds. Among the various CO2 functionalization processes known, the cycloaddition of CO2 to epoxides has gained considerable interest owing to its 100% atom‐economic nature producing cyclic carbonates or polycarbonates in high yield and selectivity. Among the various classes of catalysts studied for cycloaddition of CO2 to cyclic carbonates, porous metal‐organic frameworks (MOFs) have gained a special interest due to their modular nature facilitating the introduction of a high density of Lewis acidic (LA) and CO2‐philic Lewis basic (LB) functionalities. However, most of the MOF‐based catalysts reported for cycloaddition of CO2 to respective cyclic carbonates in high yields require additional co‐catalyst, say tetra‐n‐butylammonium bromide (TBAB). On the contrary, the co‐catalyst‐free conversion of CO2 using rationally designed MOFs composed of both LA and LB sites is relatively less studied. In this review, we provide a comprehensive account of the research progress in the design of MOF based catalysts for environment‐friendly, co‐catalyst‐free fixation of CO2 into cyclic carbonates.

Development of a heterogeneous catalyst composed of a [Zn(ii)NMeTPyP]4+[I−]4 complex immobilized in PCN-224 for environment-friendly, co-catalyst-free fixation of CO2 is reported.