Unraveling the intricate solvent-catalyst interplay in TS-1 catalyzed benzene hydroxylation: Experimental and molecular simulation insights

The direct hydroxylation of benzene with hydrogen peroxide (H 2 O 2 ) over titanium silicalite-1 (TS-1) offers an environmentally benign route to phenol, though its efficiency is highly dependent on the solvent environment. By integrating experimental and theoretical approaches, this study reveals the underlying mechanism. Water uniquely boosts benzene conversion to 45.8% through synergistic effects. It serves as a proton-transfer mediator to lower the activation barrier (Δ G ), enhances the electrophilicity of Ti-active sites via increased maximum electrostatic potential (ESP max ), and leverages the hydrophobic pores of TS-1 to enrich benzene near the active sites. However, this this multifunctional enhancement also promotes over-oxidation, limiting phenol selectivity to 42.8%. In contrast, the organic solvents suppress consecutive oxidation and achieve high selectivity above 70% due to their larger HOMO-LUMO energy gaps ( E gap ). Yet they exhibit low activity owing to higher energy barriers, weaker electrophilicity, and competitive adsorption. This work further establishes quantitative correlations between catalytic performance and key descriptors such as Δ G , ESP max , and E gap , providing a predictive framework for rational solvent selection in TS-1 catalysis.