Improving selective hydrogenation of carbonyls bond in α, ß-unsaturated aldehydes over Pt nanoparticles encaged within the amines-functionalized MIL-101-NH2.

ABSTRACT

The high selectivity in the hydrogenation reactions of α, ß-unsaturated aldehydes is always a demanding task. Precious Pt-based catalysts play a pivotal role in selective catalytic hydrogenation of α, ß-unsaturated aldehydes, but controlling the selectivity is still a great challenge. Herein, the Pt nanoparticles were encaged within the mesopores of amines (-NH2) functionalized MOFs via polyol reduction method as an efficient approach to enhance the selectivity of desired carbonyls bond reduction. The as-prepared 3-Pt/MOF-NH2(x) catalysts retained the inherent properties of MOF-NH2(x) supports such as crystallinity, surface area, pore texture, and surface acidity. Remarkably, the amines modified MOFs supported Pt-based catalysts (3-Pt/MOF-NH2(x)) improved the selective hydrogenation of carbonyls (CO) bond in cinnamaldehyde (CAL) and Furfural (FFL) with a higher selectivity (≥80 %) under mild conditions as compared to other reported catalysts. The improved catalytic performance for the selective hydrogenation of carbonyls (CO) bond is credited to the nitrogen (N) heteroatom of the amines group existing in the skeleton of MOFs and somewhat to the steric effect induced by mesopores of MOFs. The N heteroatom not only helps in the high uniform dispersion and stabilization of small-sized Pt nanoparticles (≈2nm) but also adjust the electron movement (electronic density) via synergistic effect resulting from the N to the vacant d-orbital of active Pt nanoparticles confined within MOFs, leading to more new interfacial electrophilic and nucleophilic sites, which are beneficial for selective hydrogenation of CO bond. Besides, the steric effect induced by mesopores of MOFs, encaging Pt nanoparticles, can also enhance the selective adsorption of the CO bond to interact with the catalyst active sites, resulting in higher selective hydrogenation of CO bond.