Rare Earth Valve Manipulates Dual Regulation of Electronic States and Adsorption Geometry in the Selective Hydrogenation of Ethynylbenzene

Abstract

The semi-hydrogenation of phenylacetylene is a fundamental reaction in the synthesis of polymer precursors. However, achieving a balance between catalytic activity and styrene selectivity remains a significant challenge due to the risk of over-hydrogenation. Herein, we design ternary Pt2-xCoxCe rare earth alloys to synergistically regulate electronic states and adsorption geometries, thereby enhancing selective hydrogenation. The optimized Pt1.5Co0.5Ce catalyst exhibits remarkable performance, achieving a 98.3% conversion of phenylacetylene, an 85.1% selectivity for styrene, and a turnover frequency (TOF) of 1549.6 h-1 under mild conditions, surpassing most reported Pt-based catalysts. In situ spectroscopy, combined with kinetic analysis, demonstrates that the catalyst facilitates the adsorption and conversion of phenylacetylene. Density functional theory (DFT) calculations reveal that directional electron transfer from Ce (4f) to Pt/Co (5d) via d-f orbital hybridization effectively modulates the position of the Pt d-band center, weakening the over-adsorption of the intermediate styrene while preserving optimal activation of phenylacetylene. Additionally, the large ionic radius of Ce spatially alters the adsorption configuration of styrene, reducing its adsorption energy and increasing the energy barrier to suppress ethylbenzene formation. This study illustrates that rare earth alloy engineering is a universal strategy to address the activity-selectivity trade-off in heterogeneous catalysis.