Deciphering Metal−Ligand Hybridization for Directing Selective C−Cl Bond Activation in HCFC-244bb Dehydrohalogenation

Selective dehydrochlorination of HCFC-244bb is a key step toward the synthesis of next-generation HFO-1234yf refrigerants, yet achieving high selectivity is hindered by competitive C−F bond activation. Herein, we report a series of Ni- and Cr-based catalysts with systematically tuned surface Lewis acidity. Mechanistically informed spectroscopic characterization and electronic structure analysis demonstrate that ligand electronegativity and metal oxidation state regulate the metal−ligand bonding continuum from predominantly covalent to increasingly ionic character. Catalytic testing reveals a pronounced trade-off between activity and selectivity, with NiO achieving an HFO-1234yf selectivity of 91.36%. Density functional theory calculations and frontier molecular orbital analyses identify the conduction band minimum (CBM) energy as a decisive electronic descriptor for selectivity. An S-shaped correlation between CBM energy and selectivity thereby emerges, providing a predictive framework for the rational design of high-performance dehydrohalogenation catalysts through band-structure engineering.