New highly porous aluminium based metal-organic frameworks: Al(OH)(ndc) (ndc = 2,6-naphthalene dicarboxylate) and Al(OH)(bpdc) (bpdc = 4,4′-biphenyl dicarboxylate)

Two aluminium based metal-organic frameworks were synthesized using a solvothermal route. Using N,N-dimethylformamide as a solvent, a new porous modification Al(OH)(ndc) (ndc = 2,6-naphthalene dicarboxylate (DUT-4, DUT = Dresden University of Technology) of a non-porous MIL-69 was received. The structure consists of chains built of aluminium coordination octahedra bridged by ndc linkers. After removal of the solvent molecules, the material has a specific pore volume of 0.68 cm3 g−1. The excess hydrogen saturation value for this compound is 2.1 wt.% (Vad,STP(H2) = 247 cm3 g−1) reached at 30 bar and −196 °C. Furthermore, a new isoreticular compound Al(OH)(bpdc) (DUT-5) was synthesized in DMF using 4,4′-biphenyldicarboxylate (bpdc) instead of ndc as linker. This compound has a high permanent porosity and a specific pore volume of 0.81 cm3 g−1. The maximum hydrogen excess adsorption is 3.3 wt.% (Vad,STP(H2) = 381 cm3 g−1) at 40 bar and −196 °C.