Two bimetallic metal-organic frameworks capable of direct photocatalytic degradation of dyes under visible light

Two bimetallic metal-organic frameworks (MOFs), specifically {2[LiM(TDA)(2)(DMF)]NH2+(CH3)(2)}(n) (M=Co (HNU-29) or Zn (HNU-30), TDA=2,5-thiophenedicarboxylate), were synthesized by solvothermal methods. X-ray crystal structures of the two MOFs showed them to be isostructural. Thus, in both cases, the metal secondary building units were connected by TDA(2-) ligands to form a 3D framework whose structure can be simplified to the twofold interpenetrated dia net. HNU-29 showed excellent photocatalytic activity for the degradation of methylene blue (MB) under visible light even without the addition of H2O2 as an electron acceptor, remaining stable even after several cycles of reuse. The MB degradation followed first-order kinetics, and the photocatalytic degradation mechanism was found to be related to the effective ligand-to-metal charge transfer within the framework.