In Situ Selective Site-Blocking Dictates Benzene Partial Hydrogenation to Cyclohexene on Zn-Promoted Ru-Based Catalysts

The partial hydrogenation of benzene to cyclohexene (CHE) represents a long-standing challenge in catalysis. Although Zn-promoted Ru-based catalysts were patented decades ago for achieving a top record of 50% CHE yield, the active sites and mechanistic origins of selectivity, specifically why the unsaturated C–C bonds in benzene are targeted over those in CHE, have remained unresolved despite four decades of research. Here, we employ large-scale machine-learning-driven global optimization to explore millions of Ru and Ru–Zn structure candidates and a complete benzene hydrogenation reaction network under realistic reaction conditions, that is, 50 atm H₂ pressures, aqueous Zn²⁺ solution. We reveal that (i) Zn²⁺ ions selectively deposit on corrugated Ru surfaces, for example, Ru(101̅0) and (101̅1), where they inhibit deep hydrogenation by blocking too active sites; (ii) partial hydrogenation occurs exclusively on close-packed Ru(0001) terraces covered with one monolayer of chemisorbed H atoms. Microkinetics simulation further confirms that the presence of Zn enhances the CHE yield from 0% to 50% by poisoning corrugated surfaces in Ru nanoparticles. Building on these atomistic insights, we propose that introducing tensile strain 2% into the Ru lattice can elevate the CHE yield to 60% with 100% CHE selectivity, highlighting the potential for tailored catalyst supports to maximize performance.