Thermo-responsive polymer grafted carbon nanotubes as the catalyst support for selective hydrogenation of cinnamaldehyde: Effects of surface chemistry on catalytic performance.

Graphical abstract Highlights • Thermosensitive Pd catalyst supported on poly(N -isopropylacrylamide) grafted carbon nanotube (CNT-PNIPAM) was constructed. • As-prepared Pd/CNT-PNIPAM was applied for selective hydrogenation of cinnamaldehyde. • The hydrophilic surface of CNT-PNIPAM at 25 °C improved the dispersion of Pd nanoparticles on it in catalyst preparation. • Pd/CNT-PNIPAM exhibited the hydrophobic surface at 80 °C, improving adsorption properties for reactants in the reaction. • High Pd dispersion on catalyst as well as its good adsorption properties resulted in an improved catalytic performance. Abstract A wettability-controllable surface on carbon nanotubes (CNTs) was successfully constructed through directly grafting poly(N -isopropylacrylamide) (PNIPAM) from CNT surface (i.e. CNT-PNIPAM) via a facile method. The hybrid was employed as the support to prepare Pd catalyst (i.e. Pd/CNT-PNIPAM) for selective hydrogenation of cinnamaldehyde (CAL). The effects of thermoresponsive surface chemistry on catalytic performance were studied. Results showed that CNT-PNIPAM had the lower critical solution temperature (LCST) at about 37 °C. The hydrophilic surface of CNT-PNIPAM at 25 °C (< LCST) improved the dispersion of Pd nanoparticles on it in catalyst preparation. As-prepared Pd/CNT-PNIPAM then automatically switched its hydrophilic surface to the hydrophobic one at 80 °C (>LCST), which exhibited the good adsorption properties for reactants in the reaction. The high Pd dispersion on Pd/CNT-PNIPAM as well as its good adsorption properties for CAL jointly resulted in an enhanced catalytic activity, meanwhile maintaining the selectivity to cinnamyl alcohol (COL) unchanged in comparison to CNT supported Pd catalyst (Pd/CNT). [ABSTRACT FROM AUTHOR]