Construction of Lanthanide Metal–Organic Frameworks for Cyclic Carbonates Synthesis by CO2 Chemical Fixation with Epoxides or Olefins

Developing lanthanide metal-organic frameworks (Ln-MOFs) for catalyzing CO₂ into chemicals is significant due to their luminescence instead of catalysis. In this work, three isostructural Ln-MOFs (Eu-MOF, Ga-MOF, and Tb-MOF) have been hydrothermally synthesized based on 4,4'-(quinoxaline-2,3-diyl)dibenzoic acid (H₂qda). Structural analyses indicate that these new MOFs show the same coordination mode with a two-dimensional, porous, and 4-connected sql net. The investigation of their performances in catalyzing CO₂ conversion shows that they can efficiently catalyze the conversion of CO₂ with epoxides to produce cyclic carbonates under solvent-free and atmospheric conditions with up to 99% conversion. Meanwhile, the catalysts show good recyclability and broad substrate adaptability. Besides, the previously reported H₂qda-based Ln-MOF (Eu-MOF-1) with a different coordination mode exhibits similar catalytic activity toward the above reaction. The catalytic data mainly suggest that these isostructural Ln-MOFs show comparably catalytic activity, revealing that the Ln nodes (Eu, Tb, and Ga) and coordination mode have a slight effect on catalytic activity in the CO₂ coupling reaction with epoxides. Further, these Ln-MOFs have been used for promoting the one-pot "oxidative carboxylation" from olefins and CO₂ to produce cyclic carbonates by the TBHP/Ln-MOF/TBAB composite, achieving over 80% yield under atmospheric conditions.