Switching Hydrogenation Selectivity in Pt/MOOH via a Tailored Ni/Co Ratio and Hydrogen Etching.

The selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) or hydrocinnamaldehyde (HCAL) is a great challenge due to the conjugated unsaturated functional groups. Exploring efficient catalysts with desirable selectivity is critical. Herein, Pt nanoparticles supported on transition metal oxyhydroxides (Pt/MOOH, M = Ni, Co) with engineered interlayer spacings are reported for pathway-tunable CAL hydrogenation. By adjustment of the Ni/Co ratio and employing hydrogen etching, the product selectivity can be effectively switched between COL and HCAL. Pt/NiOOH achieves 94.1% HCAL selectivity, while hydrogen-etched Pt/CoOOH shifts the selectivity toward COL (92.5%). Integrated experimental and characterization results reveal that the selective hydrogenation pathways depend critically on the transition metal composition and intrinsic properties of the support. Furthermore, in situ Fourier transform infrared spectroscopy combined with density functional theory calculations confirms preferential η⁴ adsorption on Pt/NiOOH, while vertical η¹(O) adsorption dominates on Pt/CoOOH-E (where E represents hydrogen-etching) and exhibits the highest adsorption energy. The versatility of this approach provides a paradigm for the design of a high-efficiency catalyst for the selective hydrogenation of α, β-unsaturated aldehydes.