Synergistic ligand anchoring and electronic modulation in CeMIL-101-NH₂ boosting ultrasmall Niδ+ sites for efficient catalytic hydrogenation.

Precise regulation of non-precious metal active species, particularly electron-deficient Niδ+ centers, is vital yet remains challenging for hydrogenation catalysis. Herein, we propose a synergistic strategy combining ligand anchoring and electronic modulation to construct a metal-organic framework (MOF), designated as CeMIL-101-NH₂ (where MIL stands for materials of institut lavoisier). This strategy enables the generation of ultrasmall Niδ+ sites, thereby facilitating efficient catalytic hydrogenation. Amino-functionalized ligands (BDC-NH2) offer strong NiN coordination anchoring ultrasmall Ni nanoparticles, while Ce doping at Cr2Ce nodes forms Ce-O-Ni bridges that promote interfacial electron transfer, thereby stabilizing Niδ+ centers. The Ni@CeMIL-101-NH2 catalyst exhibits outstanding hydrogenation activity, giving a 100 % selectivity toward tetrahydrodicyclopentadiene (THDCPD) with 100 % conversion of dicyclopentadiene (DCPD) at 100 °C, 2 MPa within 1.5 h, compared with Ni@MIL-101-BDC (19.5 % THDCPD selectivity) and Ni@MIL-101-NH2 (74.6 % THDCPD selectivity). Replacing Ce with La, Eu, or Fe significantly reduces THDCPD selectivity to 70.6, 25.6, and 4.2 %, respectively. Density functional theoretical (DFT) calculation revealed that the more negative charge density difference (-1.90 vs. -1.85 eV) and more apparent hydrogen spillover processes (0.63 vs. 0.94 eV) in the Ni4/CeCr2-SBU-NH2 clusters compared to Ni10/Cr-SBU-BDC clusters. Finally, the catalyst maintains high activity and structural integrity over 10 cycles without detectable Ni leaching. The proposed dual optimization strategy offers deep insights for designing efficient and durable MOF-based hydrogenation catalysts.