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

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.