Two novel organic phosphorous-based MOFs: synthesis, characterization and photocatalytic properties

Two novel metal-organic framework (MOF) photocatalysts with different structures [(Cu(H2L)(4,4'-bipy)0.5(H2O)] (1) and [Co(C14H14O6.5P2)(4,4'-bipy)0.5(H2O)2]·H2O (2) were synthesized using a hydrothermal method using a phosphonate ligand [H4L = 1,1'-biphenylene-4,4'-bis(methylene)-bis(phosphonic acid)] and 4,4'-bipyridine ligand. All the samples were characterized by elemental analysis, thermal analysis, and single crystal X-ray diffraction. As novel porous materials, the two complexes showed active performance for the reduction of Cr(vi) to Cr(iii) and the photodegradation of methylene blue (MB) dye in aqueous solution under UV light. Control experiments showed that the pH value was vital for Cr(vi) reduction, meanwhile, the use of a hole scavenger of methanol promoted the photocatalytic reduction significantly. It was also demonstrated that complexes 1 and 2 were efficient for the degradation of MB. Moreover, the possible reaction mechanism of the reaction was also investigated in detail. Finally, the cyclic experiments indicated the two photocatalysts were stable and reusable, enabling them to be potential candidates for use in environment governance.