Attempt to Generate Strong Basicity on Silica and Titania

Abstract

Modification and control of surface function on porous materials have been a very promising and appealing area of chemistry. In this paper, the reason as to why it is impossible to generate a strong basicity on silica and titania is explored in detail, and consequently, a new strategy was adopted to overcome this obstacle, not only to obtain a solid strong base derived from silica and titania for the first time but also in a new environmentally benign way. Base precursor KNO3 was loaded on silica and titania along with alumina and zirconia for comparison. Varied dispersion and thermal decomposition behavior of KNO3 on these supports as well as the different resulting basicity of the composites were delineated, and the surface vacant sites and electronegativity of cations in supports were proven to be responsible for such differences. Further, a redox strategy was employed to convert the supported KNO3 to basic sites at relatively mild conditions, through which a strong basicity was finally generated on silica and titania, while superbasicity was formed on alumina and zirconia. Moreover, the present redox strategy could significantly reduce the release of harmful gases such as nitrogen oxides, which is beneficial to the protection of the environment. The different mechanisms for the thermal activation and redox approach on the preparation of solid strong basic materials were determined.