A Green Chemo-Enzymatic\nApproach for CO<sub>2</sub> Capture and Transformation into Bis(cyclic\ncarbonate) Esters in\nSolvent-Free Media

A sustainable approach\nfor CO<sub>2</sub> capture and\nchemo-enzymatic\ntransformation into bis(cyclic carbonate) esters from CO<sub>2</sub>, glycidol, and organic anhydrides under solvent-free conditions\nhas been demonstrated. The chemo-enzymatic process is based on two\nconsecutive catalytic steps, which can be executed through separated\noperations or within a one-pot combo system, taking advantage of the\nsynergic effects that emerge from integrating ionic liquid (IL) technologies\nand biocatalysts. In a first step, lipase-catalyzed transesterification\nand esterification reactions of different diacyl donors (e.g., glutaric\nanhydride, succinic anhydride, dimethyl succinate, etc.) with glycidol\nin solvent-free under mild reaction conditions (70 °C, 6 h) produce\nthe corresponding diglycidyl ester derivatives in up to 41% yield.\nBy a second step, the synthesis of bis(cyclic carbonate) esters was\ncarried out as a result of the cycloaddition reaction of CO<sub>2</sub> (from an exhausted gas source, 15% CO<sub>2</sub> purity) on these\ndiglycidyl esters, catalyzed by the covalently attached 1-decyl-2-methylimidazolium\nIL (supported ionic liquid-like phase, SILLP), in solvent-free condition,\nleading up to 65% yield after 8 h at 45 °C and 1 MPa CO<sub>2</sub> pressure. Both key elements of the reaction system (biocatalyst\nand SILLP) were successfully recovered and reused for at least 5 operational\ncycles. Finally, different metrics have been applied to assess the\ngreenness of the solvent-free chemo-enzymatic synthesis of bis(cyclic\ncarbonate) esters here reported.