Graphene Oxide-Supported Catalyst with Thermoresponsive Smart Surface for Selective Hydrogenation of Cinnamaldehyde

Abstract

In this study, a graphene oxide (GO)-based thermoresponsive smart catalytic material with a phase-transition temperature of approximately 37 °C was developed by growing poly(N-isopropylacrylamide) (PNIPAM) on GO sheets (i.e., GO-PNIPAM). The composite was characterized by Fourier transform infrared spectroscopy, N2 adsorption, thermogravimetric analysis, organic elemental analysis, differential scanning calorimetry, and X-ray photoelectron spectroscopy. GO-PNIPAM-supported Ru catalysts (i.e., Ru/GO-PNIPAM) were then prepared for cinnamaldehyde (CAL) hydrogenation. The influence of thermosensitive smart surface on the reaction was investigated. Results indicated that GO-PNIPAM exhibited the hydrophilic surface at 25 °C, which resulted in highly dispersed Ru nanoparticles on the composite. Afterward, the surface wettability of Ru catalyst was spontaneously changed to hydrophobicity at 70 °C that greatly improved CAL sorption on the catalyst in the reaction. The synergistic effect between Ru and GO-PNIPAM as well as the great adsorption ability to reactants on Ru/GO-PNIPAM jointly resulted in the enhancement of catalytic activity over it in comparison to that over GO-supported Ru catalyst (Ru/GO). Meanwhile, the hydrophobic surface of Ru/GO-PNIPAM at a high-temperature preferred C═O adsorption mode, yielding a higher cinnamyl alcohol selectivity than Ru/GO did.