A Monodispersed Spherical Zr-Based Metal–Organic Framework Catalyst, Pt/Au@Pd@UIO-66, Comprising an Au@Pd Core–Shell Encapsulated in a UIO-66 Center and Its Highly Selective CO₂ Hydrogenation to Produce CO

A Zr-based metal–organic framework (MOF) catalyst, Pt/Au@Pd@UIO-66, is assembled, where UIO-66 is Zr₆O₄(OH)₄(BDC)₆ (BDC = 1,4-benzenedicarboxylate). The gold nanoparticles (NPs) act as the core for the epitaxial growth of Pd shells, and the core–shell monodispersed nanosphere Au@Pd is encapsulated into UIO-66 to control its morphology and impart nanoparticle functionality. The microporous nature of UIO-66 assists the adsorption of Pt NPs, which in turn enhances the interaction between NPs and UIO-66, favoring the formation of isolated and well-dispersed Pt NP active sites. This MOF exhibits high catalytic activity and CO product selectivity for the reverse-water–gas-shift reaction in a fixed-bed flow reactor.