Efficient CO2 capture/utilization by Co(ii) MOF as a heterogeneous catalyst in CO2–epoxide cycloaddition at ambient condition has been investigated and correlated with computational studies.

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The synthesis and characterization of a mixed ligand metal–organic framework (MOF) with good thermal and chemical stability, {[Co­(BDC)­(L)·2H2O]·xG} n (CoMOF-2), involving an aromatic dicarboxylate (H2 BDC = 1,4-benzenedicarboxylic acid) and an acyl-decorated N-donor linker [L = (E)-N′-(pyridin-4-ylmethylene) isonicotinohydrazide] by various physicochemical techniques, including Single crystal X-Ray Diffraction (SXRD), are reported. The MOF showed a good affinity for CO2 capture, and Grand Canonical Monte Carlo simulation studies exposed strong interactions of CO2 with the functionalized N-donor ligand of the framework. CoMOF-2 and KI act as an efficient binary catalyst for the sustainable utilization of CO2 with spiro-epoxy oxindole to spirocyclic carbonate under ambient conditions. Notably, herein we report MOF-based catalysis for the cycloaddition of oxindole-based epoxides with CO2 for harvesting new spirocyclic carbonates. Interestingly, we could isolate and crystallize six of the spirocyclic carbonate products, and the structure of the newly synthesized molecules has been established by SXRD analysis. We present a plausible proposed catalytic mechanism through activation of the epoxide ring by the Lewis acidic/basic sites present on the framework surface that is validated by molecular modeling.

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Mixed‐ligand 3 D/2 D Zn metal–organic frameworks (MOFs) {[Zn(bdc)(L1)]⋅x G}n (ZnMOF‐1) and {[Zn(ipa)(L2)]}n (ZnMOF‐2; in which H2BDC=benzene‐1,4‐dicarboxylic acid, L1=4‐pyridyl carboxaldehyde isonicotinoylhydrazone, H2IPA=isophthalic acid, L2=3‐pyridyl carboxaldehyde nicotinoyl hydrazone, and G=lattice guests) were synthesized using versatile synthetic routes that include a green mechanochemical (grinding) reaction. Chemical and thermal stability, phase purity, and characterization of the ZnMOFs synthesized by different approaches were established by using various analytical methods. Both ZnMOFs can be used as a highly active, solvent‐free, binary catalyst for CO2 cycloaddition with epoxides under ambient reaction conditions of 1 atm pressure and room temperature/40 °C, in the presence of the cocatalyst nBu4NBr. The yield, recyclability, and stability of ZnMOF‐1 as a potential catalyst towards epoxide to cyclic carbonate conversion are excellent under ambient conditions. From literature and experimental inferences, a rationalized mechanism mediated by the Zn center of ZnMOFs for the CO2‐epoxide cycloaddition reaction has been proposed. To the best of our knowledge, very few MOF‐based catalysts have been reported to realize the conversion of CO2 to useful products under similar mild conditions. In the present investigation, that is, catalyst preparation by green mechanochemical synthesis and catalysis under ambient, solvent‐free conditions were performed with minimum energy utilization.

Developing a strategy to synthesize an unprecedented and previously unknown organic molecule is especially appealing. The design, synthesis, and development of a new class of spiro-cyclic carbonates are reported. An efficient process involving the cycloaddition reaction of spiro-epoxyoxindoles with CO2 (balloon) has been demonstrated using deep eutectic solvent (DES). The reaction can be carried out under mild reaction conditions to afford desired spiro-cyclic carbonates in excellent yields (up to 98%). The product could be separated easily, and the DES was reusable four times with retention of its activity.