Sustainable Synthesis of Cyclic Carbonates from Terminal Epoxides by a Highly Efficient...

The nonstopping increment of atmospheric carbon dioxide (CO₂) concentration keeps harming the environment and human life. The traditional concept of carbon capture and storage (CCS) is no longer sufficient and has already been corrected to carbon capture, utilization, and storage (CCUS). CCUS involves significant CO₂ utilization, such as cyclic carbonate formation, for its cost effectiveness, less toxicity, and abundant C1 synthon in organic synthesis. However, the high thermodynamic and kinetic stability of CO₂ limits its applications. Herein, we report a mild, efficient, and practical catalyst based on abundant, nontoxic CaI₂ in conjunction with biocompatible ligand 1,3-bis[tris(hydroxymethyl)-methylamino]-propane (BTP) for CO₂ fixation under atmospheric pressure with terminal epoxides to give the cyclic carbonates. The Job plot detected the 1:1 Ca²⁺/BTP binding stoichiometry. Furthermore, formation of a single crystal of the 1:1 Ca²⁺/BTP complex was confirmed by single-crystal X-ray crystallography. The bis(cyclic carbonate) products exhibit potentials for components in the non-isocyanate polyurethanes (NIPUs) process. Notably, this protocol shows attractive recyclability and reusability.