Microenvironment of MOF Channel Coordination with Pt NPs for Selective Hydrogenation of Unsaturated Aldehydes

Surface and interface states of noble metal nanoparticles (MNPs), closely related to the catalytic performance, have been of great concern to academics in the field of catalysis. The catalytic property of MNPs was usually regulated through introducing modifier effects and metal-support effects, and the common nature of these strategies involved either the construction of steric hindrance on the surface of MNPs or the regulation of surface electronic state of MNPs, which inspired us to employ metal-organic frameworks (MOFs) as a support due to their tailorable physical-chemical environments. Herein, we utilized the MOF matrixes to encapsulate MNPs (MNPs@MOFs) as catalysts which showed good selectivity and high conversion in the hydrogenation reaction of the citronellal molecule. Three kinds of Pt@MOF catalysts (Pt@ZIF-8, Pt@ZIF-67, and Pt@UiO-66) with different channel environments (pore size, metal sites, etc.) were designed, and it was found that Pt@ZIF-67 exhibited comparable selectivity (>99%) and higher activity (turnover frequency = 42.28 h-1). The high selectivity toward unsaturated alcohols was derived from the steric effect of the ZIF-67 pore, which regulated the diffusion status of the citronellal molecule in the channels, while the high catalytic activity of MNPs originated from the electronic effect between ZIF-67 and Pt NPs. Such results were also validated by the molecular dynamic simulation and density functional theory calculation, further demonstrating that unsaturated alcohols can be formed through the selective hydrogenation of unsaturated aldehydes by reasonably designing the channel environment of MNPs/MOFs that regulated the steric and electronic effects simultaneously.