Bifunctional Mesoporous Organosilica Materials and Their Application in Catalysis: Cooperative Effects or Not?

The synthesis and characterization of a new periodically ordered mesoporous organosilica material (PMO) containing aniline as a bridging organic building block is presented. Furthermore, the coordination of the vanadyl cation [VO]2+ to the carboxy function of a second PMO material containing benzoic acid is described. Bifunctional materials containing both mentioned functional groups in different amounts (HOOC-PhSi2O3)1−x(H2N-PhSi2O3)x have been prepared. The investigation of the dipolar coupling of [VO]2+ coordinated to the benzoic acid groups via EPR spectroscopy has been used to derive a detailed picture about the surface structure of the pores on the molecular scale. The catalytic activity of the bifunctional materials in a two-step chemical transformation is investigated as a possible application. The vanadyl group catalyzes the cleavage of an acetal followed by Knoevenagel condensation catalyzed by aniline. A cooperative effect of the two groups has been observed which is, however, not caused by a s...