Defective h-BNs-Supported Pd Nanoclusters: An Efficient Photocatalyst for Selective Oxidation of 5-Hydroxymethylfurfural.

5-hydroxymethylfurfural (HMF) is one of the most promising biomass-based chemicals that is used to produce many kinds of important compounds. Especially, the selective conversion of HMF to 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), an important chemical feedstock, has high industrial significance but is technically challenging. In this study, we present a high-performance photocatalyst for selective oxidation of HMF to HMFCA. By integrating an ultrasmall amount of palladium (Pd) nanoclusters (1.12‰ in weight) on defective hexagonal boron nitride nanosheets (Pd/defective h-BN nanosheets (dh-BNs)), outstanding photocatalytic performance can be achieved, resulting in up to a 95% HMF conversion ratio with an 82% HMFCA selectivity. The performance is considerably higher than that of pristine dh-BNs and Pd on defect-free h-BNs. More importantly, this Pd/dh-BNs catalyst maintains a high catalytic activity after eight cycles, demonstrating robust catalytic stability. Density functional theory calculations indicate that Pd/dh-BNs can lower the energy barrier for HMF oxidation and facilitate the desorption of HMFCA, which contributes to the high selectivity catalytic performance. This study not only introduces a promising photocatalyst for sustainable chemical transformations but can also provide valuable insights into the design of advanced photocatalytic material for biorefinery applications.