Atomically dispersed noble metal-free Cu(I) sites in Ce-MOF-808 with enhanced catalytic hydrogenation performance

Abstract

Single-atom catalysts (SACs) catalysts have unique electronic properties and geometric structures, offering maximum atom-utilization efficiency. Noble metal-free SACs anchored within metal–organic frameworks (MOFs) enable precise tuning of electronic structures and significantly enhance catalytic activity beyond conventional porous materials. Herein, we synthesized the synthesis of Cu(I)/Ce-MOF-808-EA by anchoring atomically dispersed Cu(II) species onto the open Ce₆ nodes of the Ce-MOF-808 framework, followed by in situ reduction to Cu(I) via ethanol treatment and thermal activation processes. The atomic dispersion and valence transformation of Cu sites on Ce-MOF-808 were confirmed by X-ray Absorption Spectroscopy (XAS), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and X-ray photoelectron spectroscopy (XPS). The resulting Cu(I)/Ce-MOF-808-EA exhibited outstanding catalytic performance for the hydrogenation of Dicyclopentadiene (DCPD), achieving 100 % conversion, 91.54 % selectivity toward Dihydrodicyclopentadiene (DHDCPD), and 8.45 % selectivity toward Tetrahydrodicyclopentadiene (THDCPD) at 100 °C, 2 MPa. Notably, Cu(I)/Ce-MOF-808-EA outperformed other transition metal catalysts (Co/Ce-MOF-808-EA, Ni/Ce-MOF-808-EA and Zn/Ce-MOF-808-EA). For the first time, Density Functional Theory (DFT) calculations, combined with experimental investigations, revealed a low-energy reaction pathway for DCPD hydrogenation, wherein Cu(I) sites, in cooperation with adjacent oxygen atoms, act as bi-active centers to heterolytically cleave H₂ into proton and hydride species (*H^δ+-H^δ-) for subsequent hydrogenation. This study underscores the potential of MOFs as versatile platforms for engineering single-atom catalysts with enhanced catalytic properties.