Thermoresponsive MXene nanocomposite catalyst with high activity and thermosensitivity for controlled heterogeneous catalysis

High-performance catalytic reactions and easy-to-recycle property of noble metal catalysts are desirable in chemical productions, and a suitably combined pathway of both homogeneous and heterogeneous catalysis is promising in this regard. Herein, a novel thermoresponsive nanocomposite catalyst is designed through the “grafting-from” reaction of the thermoresponsive motifs and the “self-reduction” reaction of the noble metal ions at transition metal carbides (MXene) surface. The prepared catalyst with Au nanoparticles as active catalytic species, poly(N-isopropylacrylamide) as thermoresponsive switch, and MXene as catalyst-carrying substrate has a superior thermoresponsiveness of phase transitions (i.e., between suspended and aggregated states in aqueous conditions), which facilitates to the control of heterogeneous catalysis by surrounding temperatures. A high turnover frequency of up to 11.73 min −1 can be achieved for the 4-nitrophenol reduction at room temperature. Notably, the reaction can be easily terminated at elevated temperatures (e.g., 40 °C), with the catalysts being separated and recovered (i.e., by precipitation) in the meantime. The nanocomposite therefore combines both merits of the homogeneous catalysts (e.g., high-performance) and the heterogeneous catalysts (i.e., easy-to-recycle) and display tunable catalytic activity at low/high temperatures. The design principle and the smart ON/OFF control of the catalytic process demonstrated in this work are promising for industrial applications.