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 (H 3 O) 7 (H 2 aeae) 3 {[Cd(H 2 O) 3 ] 2 [H 3 O⊃(V 2 BP 2 O 12 ) 6 ]}·15H 2 O (1, aeae = 2-(2-aminoethylamino)ethanol) and (H 3 O) 5 (H 2 aeae) 3 {[TM(H 2 O) 2.5 (H 2 aeae) 0.5 ] 2 [H 3 O⊃ (V 2 BP 2 O 12 ) 6 ]}·9H 2 O [TM = Mn(2), Co(3)] were hydrothermally prepared and structurally characterized. The three vanadium borophosphates contain similar 12-member ring crown-shaped clusters [(V 2 BP 2 O 12 ) 6 ] 18- based on the linkage of six [V 2 O 8 ] dimers and six [BP 2 O 10 ] units. The [(V 2 BP 2 O 12 ) 6 ] 18- cluster is further bridged by the unsaturated [Cd(H 2 O) 3 ] 2+ or [TM(H 2 O) 2.5 (H 2 aeae) 0.5 ] 3+ complexes to build new types of open-framework vanadium borophosphates with pores and cavities retained by the protonated H 2 aeae 2+ , H 3 O + and free H 2 O. Surprisingly, the monodentate H 2 aeae 2+ 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.