New types of open-framework vanadium borophosphates with photocatalytic properties

Abstract

The exploration of new open-framework polyoxometalates is of very significance in structural chemistry and material science. Herein, three new organic hybrid three-dimensional vanadium borophosphates (H3O)7(H2aeae)3{[Cd(H2O)3]2[H3O⸧(V2BP2O12)6]}·15H2O (1, aeae = 2-(2-aminoethylamino)ethanol) and (H3O)5(H2aeae)3{[TM(H2O)2.5(H2aeae)0.5]2[H3O⸧ (V2BP2O12)6]}·9H2O [TM = Mn(2), Co(3)] have been hydrothermally prepared and structurally characterized. Three vanadium borophosphates contain similar 12-member ring crown-shaped cluster [(V2BP2O12)6]18- based on the linkage of six [V2O8] dimers and six [BP2O10] units. The [(V2BP2O12)6]18- cluster is further bridged by the unsaturated [Cd(H2O)3]2+ or [TM(H2O)2.5(H2aeae)0.5]3+ complexes to build new types of open-framework vanadium borophosphates with pores and cavities retained by the protonated H2aeae2+, H3O+ and free H2O. Surprisingly, the monodentate H2aeae2+ ligand coordinating with a metal center is firstly observed in 2 and 3 to date, because the aeae molecule usually acts as the trichelating ligand. Their optical absorption edges are determined to be in the range of 2.61-2.68 eV by using solid UV-vis spectra. 1-3 show the excellent photocatalytic activity for methylene blue (MB) degradation under visible-light irradiation, which present the first example of organic hybrid open-framework vanadium borophosphates as the photo-catalysts for MB degradation.