Redirecting Reaction Pathway in Tandem Catalysis With Isolated Metal-Acid Architecture.

Abstract

The rational design of metal-acid bifunctional catalysts is critical for tandem catalysis. However, the precise control of intermediate formation and conversion remains challenging due to indiscriminate reactant access to both metal and acid centers. Herein, we utilize the steric hindrance of the sodalite (SOD) framework to exclude bulky benzene and cyclohexene from accessing the metal sites, confining intermediate cyclohexene formation and conversion exclusively to acidic domains and breaking the conventional competitive pathway of cyclohexene migration from metal to adjacent acid sites. Experimentally, Ru nanoparticles were confined within the SOD framework (Ru@SOD), and distal acid sites were introduced by mixing with HY zeolite. In-depth studies reveal that coupled hydrogenation-alkylation reactions over HY domains drive a hydrogen pump effect, which continuously draws active hydrogen spillover from encapsulated Ru sites to sustain efficient benzene hydroalkylation. Such isolated metal-acid architecture redirects the pathway from a competitive hydrogenation/alkylation to an acid-driven alkylation mediated by hydrogen spillover. At ∼40% benzene conversion, 75.6% cyclohexylbenzene (CHB) selectivity and a record-high 47.3% CHB yield were achieved with the Ru@SOD + HY catalyst, significantly outperforming reference samples and other catalysts reported to date. This work provides a universal spatial isolation of metal-acid sites to modulate intermediate evolution and optimize selectivity in complex tandem catalysis.