PdZn intermetallic compound stabilized on ZnO/nitrogen-decorated carbon hollow spheres for catalytic semihydrogenation of alkynols

Enhancing the selectivity of noble metal catalysts through electronic modulation is important for academic research and chemical industrial processes. Herein, we report a facile sacrificial template strategy for the synthesis of PdZn intermetallic compound (3–4 nm) highly distributed in ZnO/nitrogen-decorated carbon hollow spheres (PdZn-ZnO/NCHS) to optimize the selectivity of Pd catalysts, which involves carbonization of a core–shell structured polystyrene (PS)@ZIF-8 precursor in an inert atmosphere, impregnation Pd precursor, and subsequent H₂ reduction treatment. Due to the unique structural and compositional features, the developed PdZn-ZnO/NCHS delivers an excellent catalytic performance for the semihydrogenation of 2-methyl-3-butyn-2-ol (MBY) to 2-methyl-3-buten-2-ol (MBE) with high activity (> 99%), high selectivity (96%), and good recyclability, outperforming the analog Pd on ZnO (Pd/ZnO) as well as the supported Pd nanoparticles (Pd/C and Pd/NC). Density functional theory (DFT) calculations reveal that the presence of Zn^δ+ species in PdZn-ZnO/NCHS alters the adsorption modes of reactant and product, leading to a decrease of the adsorption strength and an enhancement of the energy barrier for overhydrogenation, which results in a kinetic favor for the selective transformation of MBY to MBE. In addition, PdZn-ZnO/NCHS was also very effective for the partial hydrogenation of dehydrolinalool to hydrolinalool.