Highly selective catalytic hydrogenation of furfural and acetophenone on S-doped mesoporous carbon sphere-supported Pd nanocluster catalyst

The efficient catalytic conversion of the biomass platform molecule furfural into biofuels or other high-valueadded chemicals is currently a research hotspot. However, the hydrogenation of furfural possesses challenges due to the occurrence of multiple side reactions that generate various by-products. Herein, S-doped mesoporous carbon spheres (CS-S) with an ordered and accessible structure were precisely designed and synthesized. Subsequently, similar to 1.8 nm Pd nanoclusters were immobilized within the radial mesoporous structure of CS-S to obtain a Pd/CS-S catalyst. This catalyst was used for the hydrogenation of furfural and acetophenone into tetrahydrofurfuryl alcohol (THFA) and 1-phenylethanol, respectively, and 99 % conversion and more than 90 % selectivity were achieved. Mechanistic study revealed that the electron-deficient Pd nanoclusters anchored on CS-S exhibit higher adsorption energies for reactant molecules, thus facilitating the pre-adsorption and activation of substrate molecules. Moreover, the Gibbs free energy for each step of the hydrogenation process is lower on the electron-deficient Pd metal surface, leading to excellent catalytic hydrogenation performance. In addition, the Pd/CS-S catalyst also exhibited remarkable recyclability and stability over multiple reaction cycles. This work facilitates the construction of stable metal nanocluster-based catalysts for enabling highly selective catalytic hydrogenation.