Visible Light Excited ESR Spectra of Poly(alkyl titanate) and Their Catalytic Activit!es for Photolysing. Aqueous-Organic Systems

Abstract

In order to create polymer catalysts which can photodecompose aqueous alcohol solutions by visible light, proper polymerization conditions of alkyl titanates were investigated. As alkyl titanate, butyl titanate (monomer and tetramer), isobutyl titanate, and isopropy l titanate were used as the starting material for polymerization. They were dissolved in tetrahydrofuran, benzene, ethanol and other solvents, and were polymerized in dark or u nder illumination of white fluorescent lamps using crushed silica gel as seeds of polymerizati on. Infrared spectra, diffuse reflectance spectra, ESR under illumination of visi b le light were measured. Their catalytic activities, using Pt as a co-catalyst, were measured by illuminat i ng visible light in the wavelength region of 480∼700 nm, and analyzing the reactio n products from the reactant consisting of 1: 1 water-2-propanol. The amount of alkyl gro u ps left in the polymer after condensation polymerization reaction varies with the different polymeriz ation conditions. The amount of alkyl group strongly affects the light absorption w avelength and the generation of paramagnetic species when illuminated by visible light. If platinum, manganese ions, etc. are added to the polymer, the electronic orbitals of those ions are contributed to the molecular orbital of the polymer molecule. Therefore, the excited el e ctrons or holes formed by light illumination move in the molecular orbital toward the m e tal ion site. It will be concluded that a sort of potential gradient toward those metal ions (Pt, Mn, and V) exists in the polymer and that the presence of such potential gradient endo ws the titanium containing polymer with photocatalytic activities for photodecomposition of alcohol to hydrogen by visible light.