Microenvironment Modulation for Electronic Structure of Atomically Dispersed Ir Species in Metal–Organic Frameworks Toward Boosting Catalytic DCPD Hydrogenation Performance

Abstract

The fine-tuning of the electronic structure and local environment surrounding the atomically dispersed metal centers is crucial in catalysis but remains a grand challenge that requires in-depth exploration. In this study, atomically dispersed Ir species were incorporated into a series of UiO-type metal−organic frameworks via the strong metal–support interactions (SMSI), and their electronic state was precisely modulated by regulating the metal-oxo clusters (Ce, Zr, and Hf) and organic ligands (BDC-X, where X = -H, -NH₂, -Me, or -NO₂) for enhancing their catalytic performance for dicyclopentadiene (DCPD) hydrogenation. The optimized Ir@Ce-UiO-66-NO₂ effectively transforms DCPD into tetrahydrodicyclopentadiene (THDCPD), giving a 100% DCPD conversion and over 99% THDCPD selectivity, far superior to the corresponding counterparts. Experimental and theoretical results jointly demonstrated that Ce-oxo clusters with unique Ce^III/Ce^IV redox pairs can facilitate the electron transfer to Ir species. Furthermore, electron-withdrawing -NO₂ groups play a crucial role in increasing the Ce^III/Ce^IV ratio, promoting the efficient electron uptake by the MOF support and leading to a low electron density around Ir species, which enhances stronger interactions between substrate molecules and active sites and contributes to the excellent catalytic activity. The findings presented in this work provide valuable insights into the rational design of advanced heterogeneous catalysts by leveraging the unique redox properties and electronic structure modulation capabilities of MOF supports.