New types of open-framework vanadium borophosphates with photocatalytic properties.

The exploration of new open-framework polyoxometalates is very significant in structural chemistry and materials science. Herein, three new organic hybrid three-dimensional vanadium borophosphates (HO)(Haeae){[Cd(HO)][HO⊃(VBPO)]}·15HO (1, aeae = 2-(2-aminoethylamino)ethanol) and (HO)(Haeae){[TM(HO)(Haeae)][HO⊃ (VBPO)]}·9HO [TM = Mn(2), Co(3)] were hydrothermally prepared and structurally characterized. The three vanadium borophosphates contain similar 12-member ring crown-shaped clusters [(VBPO)] based on the linkage of six [VO] dimers and six [BPO] units. The [(VBPO)] cluster is further bridged by the unsaturated [Cd(HO)] or [TM(HO)(Haeae)] complexes to build new types of open-framework vanadium borophosphates with pores and cavities retained by the protonated Haeae, HO and free HO. Surprisingly, the monodentate Haeae ligand coordinating with a metal center was observed in 2 and 3 for the first time as the aeae molecule acted as the trichelating ligand. Their optical absorption edges were determined to be in the range of 2.61-2.68 eV using solid-state UV-vis spectroscopy. 1-3 exhibited excellent photocatalytic activity towards methylene blue (MB) degradation under visible light irradiation, which presented the first example of organic hybrid open-framework vanadium borophosphates as the photo-catalysts for MB degradation.