Cycloaddition of CO₂ with an Epoxide-Bearing Oxindole Scaffold by a Metal-Organic Framework-Based Heterogeneous...

The synthesis and characterization of a mixed ligand metal-organic framework (MOF) with good thermal and chemical stability, {[Co(BDC)(L)·2H₂O]·xG} (CoMOF-2), involving an aromatic dicarboxylate (H₂BDC = 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.