Abstract
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 (eta 2-H2) binding. These results provide guiding principles for designing coordination complex-based porous materials for ambient-relevant hydrogen storage.