Confinement of Ultrasmall Cu/ZnO_x Nanoparticles in Metal-Organic Frameworks for Selective Methanol Synthesis from Catalytic Hydrogenation of CO₂

The interfaces of Cu/ZnO and Cu/ZrO₂ play vital roles in the hydrogenation of CO₂ to methanol by these composite catalysts. Surface structural reorganization and particle growth during catalysis deleteriously reduce these active interfaces, diminishing both catalytic activities and MeOH selectivities. Here we report the use of preassembled bpy and Zr₆(μ₃-O)₄(μ₃-OH)₄ sites in UiO-bpy metal-organic frameworks (MOFs) to anchor ultrasmall Cu/ZnO_x nanoparticles, thus preventing the agglomeration of Cu NPs and phase separation between Cu and ZnO_x in MOF-cavity-confined Cu/ZnO_x nanoparticles. The resultant Cu/ZnO_x@MOF catalysts show very high activity with a space-time yield of up to 2.59 g_MeOH kg_Cu^-1 h^-1, 100% selectivity for CO₂ hydrogenation to methanol, and high stability over 100 h. These new types of strong metal-support interactions between metallic nanoparticles and organic chelates/metal-oxo clusters offer new opportunities in fine-tuning catalytic activities and selectivities of metal nanoparticles@MOFs.