Ethylene Oligomerization on Defective Metal–Organic Framework HKUST-1-Supported Dihydrides: A Computational Investigation

This study presents a computational investigation into the catalytic performance of defective metal-organic framework HKUST-1-supported dihydrides (2H-<i>M</i>-DHKUST-1, <i>M</i> = Co, Ni, Ru, Rh, or Pd) for ethylene oligomerization. Through density functional theory calculations, we explore the competitive pathways (dimerization, trimerization, and isomerization) on 2H-<i>M</i>-DHKUST-1 by considering various multiplicity states for possible spin crossing. The stable electronic configurations and bonding behaviors of the metal sites are examined for their influence on catalytic activity. Natural bond orbital (NBO) charges in various intermediates and transition states are analyzed to quantify their correlations with Gibbs energies. Among the dihydrides under study, 2H-Co-DHKUST-1 and 2H-Ni-DHKUST-1 demonstrate superior activity in ethylene dimerization with the lowest energy barrier for C-C coupling, while 2H-Ru-DHKUST-1 and 2H-Rh-DHKUST-1 display exceptional selectivity toward 1-butene due to a lower energy barrier for β-hydride elimination than for trimerization. The octahedral environment of the defective HKUST-1 paddlewheel is shown to play a crucial role in limiting isomerization. Comparatively, dihydrides are more efficient than monohydrides for ethylene oligomerization. These findings provide valuable microscopic insights into the fundamental mechanisms of ethylene oligomerization on 2H-<i>M</i>-DHKUST-1, instrumental in the rational design of new catalysts for highly efficient and selective ethylene oligomerization.