Acceptorless dehydrogenation of ethanol by Ru(II) complexes with tridentate Schiff-base ligands

Hydrogen, often hailed as the purest form of energy, is renowned worldwide for its exceptional energy density, renewability, and pivotal role in driving sustainable societal progress. However, safe, efficient, and cost-effective storage of hydrogen remains a significant challenge. Ethanol, as a liquid organic hydrogen carrier (LOHC), offers a notable solution with its high hydrogen content, eco-friendliness, and cost efficiency. In this work, hydrogen production by acceptorless dehydrogenation of ethanol (ADE) catalyzed by two new Ru(II) complexes (C1 and C2) with Schiff-base ligands was explored. Under optimized conditions, these catalysts produced respectable turnover numbers (TONs) of 19,398 and 31,965, respectively, comparing favorably with other homogeneous catalysts in the same capacity. Notably, the hydrogen gas produced is free of any CO, which is critical for the hydrogen-based fuel-cell application. Ethyl acetate, the byproduct of this process, can be recycled for other purposes. A mechanism possibly responsible for the observed catalysis was proposed based on an intermediate identified by the mass spectroscopic analysis of the reaction mixture.