Mechanism-guided elaboration of ternary Au–Ti–Si sites to boost propylene oxide formation

Summary Mechanism-guided catalyst design and engineering at the scale of active sites has been developed as a powerful tool for boosting catalytic performance. Herein, we report an efficient selective silylation strategy for the elaborate fabrication of ternary Au–Ti–Si sites to boost propylene epoxidation with H2 and O2. Kinetics (isotopic) analysis, Fourier transform infrared measurements, and theoretical calculations indicate an urgent necessity for selective consuming silanol sites not only to suppress propylene oxide (PO) ring opening to byproducts promoted by H2 spillover but also to minimize PO inhibition effects. A continuous silylation treatment was developed to encourage the kinetically favorable formation of ternary Au–Ti(–OH)–Si(–O–SiR3) moiety. This delivers significantly improved H2 efficiency of 42.5% in addition to the promising PO formation rate of 193 g h−1 kgcat−1 and PO selectivity of 95.7% with the long-term stability in excess of 200 h. These insights could pave the way for rationally fabricating catalyst active sites toward optimized performance.