TS-1 Synthesis via Subcrystal Aggregation: Construction of Highly Active Hydrogen-Bonded Titanium Species for Alkene Epoxidation

Theconstruction and determination of highly active Ti sites compriseone of the most significant challenges in the rational design andsynthesis of Ti-containing porous catalysts. The pathway to efficientlybuild highly catalytically active titanium species remains to be proposedin spite of deliberate post treatments or ambiguous batch compositionadjustments. In this study, we developed a bottom-up strategyto construct a TS-1 catalyst with highly active hydrogen-bonded Tispecies via subcrystal aggregation crystallization. The microstructureof the hydrogen-bonded Ti species was verified by vacuum FT-IR and H-1 MAS SSNMR spectroscopies. Noteworthy features of the hydrogen-bondedTi species were also revealed, including a pentahedral coordinationstate and Bronsted acidity, as identified by the UV-Raman,XPS, XAFS, and FT-IR spectra of adsorbed pyridine. Significantly,the hydrogen-bonded Ti species exhibits extraordinary activity inallyl chloride epoxidation (nearly 70% higher than that of traditionalTi species). This study provides a new approach to building highlyactive Ti sites, which may provide new insights into the design andsynthesis of high-performance titanosilicate catalysts.