Sol–gel reaction of titanium phosphonate alkoxide cluster

Abstract

AbstractThe synthesis and properties of titanium phosphonate cluster molecules have been investigated; however, nothing has been done to study not only the catalytic ability of a hydrolyzed cluster but also a behavior of hydrolysis–polycondensation by solvents. The sol–gel reaction of [Ti4(μ3‐O)(OiPr)5(μ‐OiPr)3(O3PPh)3]·thf (Ti4P3Ph) was performed in tetrahydrofuran (THF), toluene, and acetone. The hydrolysis–polycondensation of Ti4P3Ph proceeded in THF and toluene, while Ti4P3Ph in acetone proceeded in two paths (hydrolysis–polycondensation and nonhydrolysis–polycondensation). The hydrolyzed Ti4P3Ph retained its cluster structure, while the calcined Ti4P3Ph at 300°C contained a collapsed cluster structure. The specific surface areas of the hydrolyzed Ti4P3Ph in THF, toluene, and acetone were 154, 302, and 7 m2 g−1, respectively. The photodegradation ability of the hydrolyzed Ti4P3Ph for methylene blue was confirmed by ultraviolet irradiation at 365 nm; however, that of the calcined Ti4P3Ph was not. It was considered that the calcined Ti4P3Ph did not retain its cluster structure. The photocatalytic ability of the hydrolyzed Ti4P3Ph was high in the order of toluene > THF > pristine > acetone. The gels retained cluster structure have higher photocatalytic ability than pristine cluster; however, the gel contained a collapsed cluster structure was found no catalytic ability.