Highly efficient chemoselective hydrogenation of unsaturated aldehydes catalyzed by hydrophobically modified core-shell defective ZIFs: Frustrated Lewis pair catalysis

Zeolitic imidazolate frameworks (ZIFs) were prepared by different methods for the chemoselective hydrogenation of biomass-derived cinnamaldehyde. It was found that the ZIFs prepared by microwave-assisted method (ZIF-67-MW) shows more defects, and the independent Lewis acid (metal center) and Lewis basic (N in 2-methylimidazole) sites in the defective ZIFs construct a heterogeneous Frustrated Lewis pairs (FLPs) system. The theoretical calculations indicate that the FLPs sites in the defec-tive ZIFs can easily dissociate the H-H bond with a low activation energy of 8.7 kcal/mol. And the silica-coated and hydrophobically modified core-shell structure of ZIF-67-MW@SiO2-DMDES is developed to enhance the stability of ZIF-67-MW and the selectivity to cinnamyl alcohol, it gives > 99% cinnamalde-hyde conversion and 95.3% selectivity to cinnamyl alcohol. Furthermore, the reaction mechanism was proposed by the combination of experimental results and theoretical calculations. The results of substrate-extending experiments show that ZIF-67-MW@SiO2-DMDES presents brighter prospects in the selective hydrogenation of a series of unsaturated aldehydes.(c) 2023 Elsevier Inc. All rights reserved.