Bio inspired design principles for next generation liquid organic hydrogen carriers: Bridging molecular biocatalysis and chemical hydrogen storage

The Liquid Organic Hydrogen Carrier (LOHC) technology offers a highly promising way for large-scale hydrogen storage and logistics. LOHC systems combine high volumetric energy density with liquid-phase handling and compatibility with the existing fuel infrastructure. However, current LOHC systems typically require elevated temperatures and precious-metal catalysts for hydrogenation and dehydrogenation. By-products formed in hydrogenation/dehydrogenation can limit catalyst stability and repetitive use of the LOHC compounds. Furthermore, a significant amount of heat is typically required for hydrogen release, which limits overall efficiency if waste heat sources are unavailable. In contrast, biological energy storage and hydrogen-conversion systems operate reversibly under mild conditions, relying on finely tuned redox cofactors, enzyme-controlled microenvironments and proton-coupled electron transfer pathways. By a comparative analysis of LOHC-based and biological hydrogen storage strategies, we highlight fundamental differences in how thermodynamic constraints are addressed at the process vs. at the molecular scale. Biological systems achieve near-reversible hydrogen conversion through precise tuning of redox windows, hierarchical energy storage and highly organized catalytic environments. LOHC technologies, in contrast, rely primarily on macroscopic control of temperature and pressure as will be exemplified for the N-ethylcarbazole/perhydro-N-ethylcarbazole LOHC system. Our contribution identifies transferable design principles from biology, including microenvironment engineering, redox mediation and coupled reaction concepts. These principles could inspire next-generation LOHC-based storage systems and catalysts to achieve milder operating conditions, improved selectivity and enhanced energy efficiency, while preserving the scalability and robustness of chemical hydrogen storage.