Dihydroxybenzoquinone as Linker for the Synthesis of Permanently Porous Aluminum Metal-Organic Frameworks

Two new dihydroxybenzoquinone-based metal-organic frameworks, ((CH3)(2)NH2)(3)[Al-4(L1)(3)(L1(center dot))(3)]center dot 3DMF (1, denoted CAU - 20) and ((CH3)(2)NH2)(3)[Al-4(L2)(3)(L2 center dot)(3)]center dot 9DMF (2, denoted CAU-20-Cl-2), were synthesized at 120 degrees C in PAU using 2,5-dihydroxy-p-benzoquinone ((C6H2(OH)(2)(O)(2)), H(2)L1) and 2,5-dichloro-3,6-dihydroxy-p-benzoquinone ((C6Cl2(OH)(2)(O)(2)), H(2)L2), respectively. Compared to other Al-MOFs, which contain carboxylate or phosphonate groups that connect the metal sites, in 1 and 2 the Al3+ are coordinated by oxido groups. The metal ions are octahedrally surrounded by oxygen atoms Of the deprotonated linker molecules to generate honeycomb layers with a metal to linker ratio of Al: L1/L2 = 2:3. The layers contain L1(2-) and L2(2-) ions as well as linker radical ions L1(center dot 3-) and L2(center dot 3-) in a molar ratio of 1 to 1. The presence of radical ions was confirmed by EPR and UV-vis-spectroscopic Measurements, and the composition was determined from a combination of PXRD, H-1, NMR, TG, and elemental analyses. Charge balance is accomplished through intercalation of (CH3)(2)NH2+ ions which are formed by partial hydrolysis of DMF. In the structures of 1 and 2 the eclipsed layers are AA and ABAB stacked, respectively, and one-dimensional hexagonal channels with diameters of ca. 9 and 6 angstrom are formed. Both compounds exhibit permanent porosity and have specific surface areas of 1440 and 1430 m(2) g(-1), respectively.