An efficient and recyclable tetraoxo-coordinated zinc catalyst for the cycloaddition of epoxides with carbon dioxide at atmospheric pressure

An efficient and recyclable catalytic system of a Zn(O)₄-coordinated complex e.g. 2-hydroxypyridine N-oxide zinc(II), Zn(OPO)₂ and tetrabutylammonium iodide (TBAI) was developed for the cyclic carbonate synthesis from epoxides and CO₂ without the use of any organic solvents. This easily prepared, low-toxic Zn(OPO)₂ may have a strong Lewis acidity for the activation of epoxides and exhibited high activity (TOF up to 22 000 h⁻¹) even at a CO₂ pressure as low as 1 bar with a broad substrate scope. Furthermore, the catalyst can be easily recovered and reused five times without a significant loss of its catalytic activity.