Biophenol-Mediated Solvent-Free Synthesis of Titanium Silicalite-1 to Improve the Acidity Character of Framework Ti toward Catalysis Application

Although titanium silicalite-1 (TS-1) with enhanced Lewis acidity can show significant catalytic functionality, the effective and green synthesis of such a TS-1 zeolite still remains a challenge. In this work, a biophenol-mediated solvent-free strategy is adopted to synthesize bio-TS-1 with an improvement of acidity character. Systematic characterizations are devoted to inspect the structural and acidic properties of the as-prepared bio-TS-1. Furthermore, density functional theory simulations are carried out to reveal the underlying mechanism for such an improvement of acidity. It is found that biophenol serving as a mediating agent realizes a homogeneous crystallization process for bio-TS-1, which fundamentally favors titanium substitution of framework sites, especially those with unique acidity. This improvement of acidity boosts the intrinsic catalytic reactivity of Ti-OOH species, further increasing the performances toward propylene epoxidation. The presented strategy together with mechanistic results clarifies the relationship between the structure and acidity in TS-1 zeolite and brings forward a promising approach to develop better TS-1 zeolites by regulating the crystallization process.