Enhancing Hydrogen Storage in UiO-Series Metal–Organic Frameworks via Ligand Functionalization and Metal Substitution Engineering

The engineering of ligand and metal node plays a pivotal role in enabling high-performance metal organic frameworks (MOFs) for efficient hydrogen storage at room temperature. This study conducts a systematic investigation into the impacts of ligand length, ligand functional groups, and doped metal atoms on the hydrogen storage performance of UiO-series MOFs. Specifically, UiO-66, UiO-67, and UiO-67-bpydc were synthesized employing H2bdc, H2bpdc, and H2bpydc ligands, respectively. Furthermore, UiO-67-bpydc-Ti/Zr samples with varying Ti incorporation ratios were prepared through an in situ metal substitution strategy. By expanding the ligand from a single benzene ring to a double benzene ring structure, incorporating nitrogen-containing heterocycles and introducing Ti species, the specific surface area of UiO-67-bpydc-Ti/Zr-0.6 increased significantly to 2487.56 m2/g, surpassing those of UiO-66 (1385.77 m2/g) and UiO-67 (1920.57 m2/g). Notably, UiO-67-bpydc-Ti/Zr-0.6 achieved a mass hydrogen storage capacity of 0.40 wt % at 298 K and 100 bar, representing significant improvements compared to UiO-66 (0.23 wt %) and UiO-67 (0.28 wt %), respectively, and exhibited good structural stability over seven cycles. XPS analysis, H2 adsorption isotherms and DFT calculations reveal that Ti doping induces a “strong-Zr, weak-Ti, negative-O” potential gradient, enhancing H2 polarization and physical adsorption stability, and thus improving hydrogen storage performance.