Two new uncommon 3D cobalt-based metal organic frameworks: Temperature induced syntheses and enhanced photocatalytic properties against aromatic dyes

The reaction of 5-fluorine-3-(3,5-dicarboxylphenxoy)benzoic acid (H3L) with cobalt(II) salt in presence of 1,1'-(1,4-butanediyl)bis (imidazole) (bib) linker yielded two new metal-organic frameworks (MOFs) with compositions [Co-4(mu(3)-OH)(2)(H2O)(2)(L)(2) (bib)(1.5)(CH3CN)center dot 3H(2)O center dot CH3CN] (1) and [Co-8(mu(3)-OH4(L)(4)(bib)(4)center dot 8CH(3)CN] (2). The single crystal X-ray diffraction revealed that 1 exhibited an unusual 3D 3,8-connected framework with 3,8T25 topology based on [Co-4(mu(3)-OH)(2)] tetranuclear cobalt clusters as secondary building units (SBU) with a (4(3)) (4(12).5(4).6(4).8(8)) Schlafli symbol. In 2, by substituting the CH 3 CN with neutral N-ligand, a 3D 3,8-connected MOF with 3,10T9 topology and a point symbol of {4(18).6(24).8(3)}.{4(3)}(2) has been obtained. This represents a highly connected uninodal network topology presently known for flexible carboxylate-based MOF systems. Both the MOFs have been used as photocatalysts for photodegradation of a model organic dye methyl violet (MV). The photocatalytic experiments demonstrated that both 1 and 2 displayed efficient photocatalytic performances to degrade MV under UV irradiation. The plausible mechanism through which both the MOFs displayed photocatalytic properties have been proposed by using band gap calculations.