Improving Ambient-Temperature Hydrogen Storage of Ni₂(m-dobdc) via Anchoring Site and Distribution of Li in Nanopores

Hydrogen is both a clean energy carrier and an essential chemical feedstock. Its widespread adoption hinges on solid sorbents that operate efficiently at ambient temperature. Among physical materials, Ni₂(m-dobdc) featuring open Ni²⁺ sites shows strong H₂ affinity and is a leading candidate. Lithium doping further enhances room-temperature capacity, yet the dopant's location, distribution, and mechanistic role remain unclear. Here, we combine experiment with molecular simulation to investigate Li incorporation in Ni₂(m-dobdc). Grand canonical Monte Carlo and molecular dynamics simulations reveal that Li⁺ preferentially anchors at bridging oxygen sites around Ni²⁺ centers, forming a homogeneous distribution that creates additional binding sites and raises the isosteric heat of adsorption from 8.3 to 12.8 kJ mol^-1. The optimal composition, 25Li@Ni₂(m-dobdc) (LiCl/Ni₂(m-dobdc) = 0.35), achieves an excess capacity of 1.99 mmol g^-1 at 298 K and 30 bar─a 33.5% improvement over the undoped framework. This work establishes a clear structure-property relationship between controlled Li decoration and ambient-temperature hydrogen storage, with the main contribution lying in mechanistic understanding. These insights offer a rational basis for optimizing hydrogen storage performance at ambient temperature.