Additive-free hydrogen production via homogeneous catalysis

Escalating environmental degradation has catalyzed a paradigm shift toward the exploration and utilization of hydrogen energy as a viable alternative to fossil fuels. The Liquid Organic Hydrogen Carriers (LOHCs), such as formic acid and methanol, represent a promising approach for achieving high-efficiency and safe hydrogen storage and transportation. However, state-of-the-art homogeneous H2 production from LOHCs strongly relies on stoichiometric amounts of external bases, severely limiting its widespread application. Herein, we develop additive-free methanol and formic acid dehydrogenation systems based on a series of newly designed ruthenium hydride complexes bearing tetradentate diazadiene-bis-phosphine ligands. These complexes exhibit a unique η4-NCCN coordination mode that enables powerful metal–ligand cooperation (MLC) by integrating a Lewis-acidic metal center and a Brønsted-basic site within a single molecular framework. Comprehensive mechanistic investigations, including spectrometric studies, kinetic isotope effect (KIE) analyses, and density function theory (DFT) calculations, were conducted to elucidate the distinct catalytic pathway and identify the corresponding rate-determining steps. Overall, this synergy of coordination chemistry, reactivity discovery, and mechanistic elucidation offers invaluable design principles for next-generation, additive-free homogeneous catalysts tailored for the hydrogenation economy.