Reversible Ambient-Temperature Hydrogen Storage through Kubas-Type Binding at Biomimetic Ni–Fe Sites on Hexagonal Boron Nitride

Reversible hydrogen storage under ambient conditions remains limited by the weak binding of physisorption and the irreversibility of atomic chemisorption. Molecular chemisorption, exemplified by Kubas-type interactions, offers an intermediate binding regime but is rarely realized in porous solids. Here, we report hydrogenase-inspired Ni–Fe biomimetic centers grafted onto in situ functionalized boron nitride nanosheets (BNNs) that reversibly bind molecular H2 under near-ambient conditions. At 298 K and 35 bar, [NiFe2]-O_BNNs reached gravimetric and volumetric capacities of 2.15 wt. % and 30 g L−1, respectively. Multitemperature isotherms fitted using a trisite Langmuir–Freundlich model yielded an adsorption enthalpy of −25.6 ± 0.3 kJ mol–1 and an entropy of −72.6 ± 0.9 J mol–1 K–1. These adsorption and thermodynamic trends indicated that metal-specific controls decoupled functional roles, with Fe-rich sites maximizing capacity, Ni-rich sites enhancing reversibility, and mixed Ni–Fe centers exhibiting the optimal balance observed in this study. Moreover, ex situ spectroscopy and diffraction analyses were consistent with a thiolate-bridged (CN)2(CO)Fe–Ni motif featuring an open coordination site compatible with side-on dihydrogen (η2-H2) binding. These results provide guiding principles for designing coordination complex-based porous materials for ambient-relevant hydrogen storage.