Decavanadate Coordination Polymers With Transition-Metal-BisTris Cations for Synergistic Atmospheric CO2 Cycloaddition.

Converting CO2 into cyclic carbonates through cycloaddition with epoxides is an attractive route for carbon utilization, but efficient and recyclable heterogeneous catalysts that operate under mild conditions remain desirable. Herein, five BisTris-modified decavanadate-based coordination polymers were prepared under mild acidic conditions. Compound 1 is assembled from [V10O28]6- anions, Na+ cations, and BisTris ligands, whereas isostructural compounds 2-5 incorporate Co2+, Ni2+, Cu2+, or Zn2+ centers as BisTris-chelated complex cations. Single-crystal analyses reveal that these transition-metal-BisTris units are integrated with decavanadate-sodium chains through hydrogen-bonding, electrostatic, and, in minor disordered components, Na-O coordination interactions, creating multiple accessible activation sites. In the cycloaddition of CO2 with epichlorohydrin, all catalysts afford >99% selectivity under 1 atm CO2 at 60°C, with the Zn-containing compound 5 giving the highest yield of 98.2%. Compounds 2-5 outperform the metal-free analogue 1, and control experiments with isolated BisTris-Co and decavanadate components confirm a cooperative contribution from vanadium Lewis acid sites, transition-metal centers, and BisTris hydroxyl groups. The best catalyst retains high activity over five cycles and shows broad epoxide tolerance, highlighting a modular strategy for constructing POM-based catalysts for mild CO2 fixation.