Highly porous and robust 4,8-connected metal-organic frameworks for hydrogen storage

Highly porous and robust metal-organic frameworks (MOFs) were constructed based on aromatics-rich octa-carboxylate ligands and copper paddle-wheel building units. Each octa-carboxylate ligand is linked to eight copper paddle wheels via the bridging carboxylate groups in a rectangular prismatic fashion to lead to very rare (4,8)-connected networks of the scu topology. The high-connectivity MOFs show remarkably high porosity and framework stability, as evidenced by a perfect agreement between experimental and theoretical surface areas and the maintenance of framework powder X-ray diffraction patterns after solvent removal. These aromatics-rich MOFs exhibit an exceptionally high hydrogen uptake of up to 2.5 wt% at 77 K and 1 atm. This work thus demonstrates the ability to construct highly porous and robust functional MOFs using multidentate bridging ligands of high connectivity. Such a rational synthetic strategy is complementary to the common reliance on high-nuclearity metal clusters for building stable and porous MOFs.