Seed‐Mediated Growth of a High‐nuclearity Titanium‐oxide Cluster with Enhanced Photocatalytic Activities in CO2/Epoxide Cycloadditions

A high‐nuclearity titanium‐oxide cluster (TOC), Ti 31 O 52 (O i Pr) 4 Bz 24 (denoted as Ti 31 ; Bz=PhCO 2 ), was synthesized via a seed‐mediated synthesis method during the solvothermal reaction of the super‐Keggin cluster Ti 17 O 24 (O i Pr) 20 (denoted as Ti 17 ) and Ti(O i Pr) 4 . Single‐crystal X‐ray diffraction analyses indicate that Ti 17 acts as a template for the addition of two Ti 7 O 6 rings to form Ti 31 . The optical absorption edge of Ti 31 slightly shifts to 446 nm, relative to the 419 nm absorption edge of Ti 17 . Ti 31 has much better visible‐light response and charge‐separation properties than Ti 17 , as confirmed by electrochemical impedance, photoluminescence spectroscopy, and transient photocurrent response. Ti 31 also shows much better activity and stability than Ti 17 in the solar synthesis of cyclocarbonate through CO 2 /epoxide cycloaddition. This study not only provides a high‐nuclearity member of the TOC family, but also suggests a potential method to enhance the photocatalytic activity of the known TOCs for more efficient solar energy harvesting.