UV Raman spectroscopic studies on transition metal-containing microporous and mesoporous materials: active sites and synthesis mechanism

This paper presents our research progresses made in UV Raman spectroscopic studies on microporous and mesoporous materials. The active sites derived from the incorporation of transition metal ions in the framework and extraframework of both microporous and mesoporous materials are characterized based on UV resonance Raman effect. The isolated transition metal ions/oxides in microporous and mesoporous materials (e.g. TS-1, Ti-MCM-41, Fe-Silicalite-1, Fe-SBA-15) are unambiguously identified by UV resonance Raman spectroscopy. In addition, the coordination environment of the transition metal ions in microporous and mesoporous materials can be sensitively differentiated by the UV Raman spectroscopy. The synthesis mechanism of microporous materials (e.g. Fe-silicalite, zeolite X), in particular microporous materials with transition metal ions substituted in framework, has been investigated by taking the advantage of UV Raman spectroscopy, which can sensitively detect the precursors and intermediates evolved in the synthesis solution and gel, while avoiding the fluorescence interference.