Encapsulating Copper Nanocrystals into Metal-Organic Frameworks for Cascade Reactions by Photothermal Catalysis

Composite materials with multifunctional properties usually possess synergetic effects in catalysis toward cascade reactions. In this work, a facile strategy to the encapsulation of octahedral Cu₂ O nanocrystals (NCs) by metal-organic frameworks (MOFs) is reported, and an oriented growth of MOF enclosures (namely, HKUST-1) around Cu₂ O NCs with desired feedstock ratio is achieved. The strategy defines the parameter range that precisely controls the etching rate of metal oxide and the MOF crystallization rate. Finally, the Cu@HKUST-1 composites with uniform morphology and controlled MOF thickness have been successfully fabricated after the reduction of Cu₂ O to Cu NCs in HKUST-1. The integration of Cu NCs properties with MOF advantages helps to create a multifunctional catalyst, which exhibits cooperative catalytic activity and improved recyclability toward the one-pot cascade reactions under mild conditions involving visible-light irradiation. The superior performance can be attributed to the plasmonic photothermal effect of Cu NCs, while HKUST-1 shell provides Lewis acid sites, substrates and H₂ enrichment, and stabilizes the Cu cores.