A dual-descriptor strategy for the rational design of low-temperature liquid organic hydrogen carriers

Liquid organic hydrogen carriers (LOHCs) are promising for safe and high-density hydrogen storage, yet their practical application is limited by the high temperatures required for dehydrogenation and by an incomplete understanding of structure-property relationships. Here, a dual-descriptor strategy is presented that combines the density functional theory (DFT)-calculated dehydrogenation reaction enthalpy (Δ_rH_d) with the pair delocalization index (PDI) as thermodynamic and kinetic descriptors for the rational screening of LOHC candidates. Using this framework, a benzodipyrrole-based BZDP1/10H-BZDP1 pair is identified, delivering a hydrogen capacity of 6.02 wt% and enabling reversible hydrogenation-dehydrogenation at temperatures as low as 363 K, clearly outperforming conventional carbazole-based and indole-based systems. Integrated experimental and theoretical analyses indicate that nitrogen incorporation destabilizes saturated intermediates by narrowing the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap and weakening C–H bonds, which lowers the activation barrier in agreement with trends predicted by the dual descriptor predictions. These results confirm the predictive reliability of the thermodynamic-kinetic design concept and offer a general route for developing next-generation low-temperature LOHC systems.