Defective Metal-Organic Frameworks Confined PdO with High Resistance to Reduction: An Efficient Photocatalyst for Hydrodeoxygenation of Lignin Derivatives.

The positively charged metal species in the supported catalyst is often highly active in various reactions, and stabilization of this state is vital for fabricating catalysts with long-term cycles, particularly under reducing reaction conditions. Herein, we propose a strategy to fabricate reduction-resistant PdO by constructing enhanced metal-support interaction (MSI) using subnanometer nodes in defective metal-organic framework (MOF). Specifically, a photo-induced way was developed to generate defected Zr6O8 nodes for enhanced MSI in nanoconfined space. The obtained Pd/defective-MOF composites not only stabilize PdO via an unsaturated Zr6O8 cluster for a long period under photoreducing conditions but also provide a driving force for substrate enrichment and proton transfer by -OH/-OH2 coordination, leading to a dramatically enhanced catalytic performance in the photocatalytic hydrodeoxygenation of lignin derivatives, which is 4.5 times that of Pd/ideal-MOF composites with weak MSI. This work provides ideas for the selection of ultrasmall support to stabilize positively charged metal and also an avenue to design photocatalysts with tightly connected heterogeneous in MOFs.