Lead-Decorated Titanium Oxide Compound with a High Performance in Catalytic CO 2 Insertion to Epoxides.

The CO 2 cycloaddition to epoxides is an efficient method for CO 2 capture and storage, important not only for reducing greenhouse gas emission but also for producing cyclic carbonates, which are valuable industrial materials. In this study, we report a novel high-nuclearity titanium oxide cluster (TOC) inlayed with main-group element Pb 2+ , H 2 Ti 16 Pb 9 O 24 (SA) 18 (DMF) 10 (OH 2 ) 2 (denoted as 1 ; SA = salicylate; DMF = N , N -dimethylformamide), which has the property of visible-light absorption and has shown high catalytic activities for cycloadditions of CO 2 under visible-light irradiation. The cluster was synthesized in a high yield in a facial solvothermal process. Its structure and electronic structure were characterized by single-crystal X-ray diffraction, density functional theory calculations, and complementary techniques. The cycloaddition reactions were performed under solvent-free conditions. While the catalytic activity due to the Lewis acidity was moderate, visible-light irradiation further folded the reaction rates. The turnover number reached 3400 with a turnover frequency of 120 h -1 . Mechanism studies indicated a synergistic effect of the Lewis acidity and photogenerated charge carriers. The performance of 1 in reversible I 2 uptake was also investigated. This study demonstrates the high potential of heterometal-decorated TOCs in the cost-effective and efficient CO 2 cycloaddition reaction under mild conditions.