Efficient Hydrogen Sorption in 8-Connected MOFs Based on Trinuclear Pinwheel Motifs

Abstract

Two new metal-organic frameworks based on trinuclear pinwheel motifs are prepared using dicarboxylate and diamine ligands. The structure of [Co3(bdc)3(dabco)] (1) (bdc = 1,4-benzenedicarboxylate; dabco = 1,4-diazabicyclo[2.2.2]octane) is described as pillared layers, whereas [Co3(ndc)3(dabco)] (2) (ndc = 2,6-naphthalenedicarboxylate) forms a variation of primitive cubic net with 3D connected pores. The two 8-connected MOFs are thermally stable at 160 and 250 degrees C for 1 and 2 respectively in the air and possess corrugated channels owing to the high connectivities of the secondary building unit. As a result, they show highly efficient hydrogen sorption capabilities. Especially, a high hydrogen uptake (2.45 wt % at 77 K and 1 bar) is observed for 2 that has the unique combination of high surface area and small portals.