Bimetallic redox sites for photochemical CO2 splitting in mesoporous silicate sieve

Abstract

Binuclear redox sites consisting of a Ti or Zr oxo-bridged to a Cu(I) or Sn(II) center have been covalently anchored on the pore surface of MCM-41 silicate sieve by a stepwise grafting procedure. The bimetallic sites feature a metal-to-metal charge-transfer (MMCT) absorption extending deep into the visible region. Covalent anchoring is manifested by low-frequency infrared modes. Irradiation of the MMCT chromophore of ZrCu(I)–MCM-41 loaded with 1 atm of CO 2 gas at RT resulted in growth of CO (2150 cm –1 ) and H 2 O (1600 cm –1 ). Photolysis experiments using 13 CO 2 and C 18 O 2 demonstrate that carbon monoxide and the oxygen atom of the water product originate from CO 2 , indicating splitting of the CO 2 upon excitation of the MMCT moiety. This is the first observation of CO 2 photoreduction at a binuclear MMCT site at the gas-solid interface. .