Enhancement of H2 Adsorption in Coordination Framework Materials by Use of Ligand Curvature

Abstract

Solvothermal reaction of the ligands H(4)L(110) ((2,7-phenanthrenediyl)diisophthalic acid) and H(4)L(111) ([2,7-(9,10-dihydrophenanthrenediyl)]diisophthalic acid) with Cu(NO(3))(2) x 2.5 H(2)O in a slightly acidified mixture of DMF/1,4-dioxane/H(2)O afforded the solvated framework compounds [Cu(2)(L(110))(H(2)O)(2)](DMF)(7.5)(H(2)O)(5) (NOTT-110) and [Cu(2)(L(111))(H(2)O)(2)](DMF)(7.5)(H(2)O)(5) (NOTT-111), respectively. Crystal structure determinations confirmed that NOTT-110 and NOTT-111 have the same NbO framework structure, differing only at the 9 and 10 positions of the phenanthrene group. The BET surface areas for desolvated NOTT-110 and NOTT-111 were estimated to be 2960 and 2930 m(2) g(-1), respectively. Compared with their phenyl analogues, introduction of phenanthrene groups to these porous Cu(II)-carboxylate framework materials leads to an enhancement of H(2) adsorption. Thus, the H(2) isotherms for desolvated NOTT-110 and NOTT-111 confirm 2.64 and 2.56 wt % total H(2) uptake, respectively, at 1 bar and 78 K. NOTT-110 shows a high total H(2) storage capacity of 7.62 wt % at 55 bar and 77 K (8.5 wt % at saturation) with a total volumetric capacity of 46.8 g L(-1) at 55 bar and 77 K.