Expanded sodalite-type metal-organic frameworks: increased stability and H(2) adsorption through ligand-directed...

The torsion between the central benzene ring and the outer aromatic rings in 1,3,5-tri-p-(tetrazol-5-yl)phenylbenzene (H3TPB-3tz) and the absence of such strain in 2,4,6-tri-p-(tetrazol-5-yl)phenyl-s-triazine (H3TPT-3tz) are shown to allow the selective synthesis of noncatenated and catenated versions of expanded sodalite-type metal-organic frameworks. The reaction of H3TPB-3tz with CuCl2.2H2O affords the noncatenated compound Cu3[(Cu4Cl)3(TPB-3tz)8]2.11CuCl2.8H2O.120DMF (2), while the reaction of H3TPT-3tz with MnCl2.4H2O or CuCl2.2H2O generates the catenated compounds Mn3[(Mn4Cl)3(TPT-3tz)8]2.25H2O.15CH3OH.95DMF (3) and Cu3[(Cu4Cl)3(TPT-3tz)8]2.xsolvent (4). Significantly, catenation helps to stabilize the framework toward collapse upon desolvation, leading to an increase in the surface area from 1120 to 1580 m2/g and an increase in the hydrogen storage capacity from 2.8 to 3.7 excess wt % at 77 K for 2 and 3, respectively. The total hydrogen uptake in desolvated 3 reaches 4.5 wt % and 37 g/L at 80 bar and 77 K, demonstrating that control of catenation can be an important factor in the generation of hydrogen storage materials.