Homogeneous catalysis in liquid organic hydrogen carriers: advances, challenges, and future directions

Abstract

Liquid organic hydrogen carriers (LOHCs) offer a promising solution for safe, efficient, and reversible hydrogen storage and transport. While heterogeneous catalysts have traditionally dominated LOHC hydrogenation and dehydrogenation, homogeneous catalysts present distinct advantages, including high selectivity, tunable active sites, and operation under milder conditions. This review systematically examines recent advances in the design and application of homogeneous catalysts for the hydrogenation and dehydrogenation of both homocyclic LOHCs, such as benzene, toluene, and naphthalene derivatives, and N-heterocyclic LOHCs, including quinolines, carbazoles, and indoles. Emphasis is placed on structure–activity relationships, mechanistic insights, and emerging trends, with a focus on catalysts based on both noble and earth-abundant metals. Beyond catalyst performance, we address key challenges in homogeneous catalyst recovery, recycling, and process integration, all of which are critical for industrial scalability. By identifying current gaps in the literature and outlining future research priorities, this work aims to guide the development of efficient, reversible, and economically viable homogeneous catalytic systems for next-generation hydrogen storage technologies.