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.