Facile synthesis of bismuth(III) based metal-organic framework with difference ligands using microwave irradiation method

In this study, we studied the effect of starting ligands such as 1,4-benzenetdicarboxylic (H2BDC), 1,3,5-benzenetricarboxylic (H3BTC), and 4,4′,4″-s-triazine-2,4,6-triyl-tribenzoic (H3TATB) acids on the photocatalytic activity of three bismuth-based MOFs (Bi-MOF) obtained via a microwave-assisted solvothermal process. Different shapes and sizes of ligands displayed different structure properties from the corresponding Bi-MOF. Specifically, Bi-MOF composed of Bi3+ and H3TATB (Bi-TATB) exhibits the largest specific surface area of 355 m2/g, highest surface-oxygen vacancy amount, a more vigorous light absorption intensity with a broader range of visible light absorption and red-shifted absorption edge than that of Bi-MOF composed of Bi3+ and H2BDC (Bi-BDC) and Bi-MOF composed of Bi3+ and H3BTC (Bi-BTC), suggesting the extension in the photocatalytic activity for Bi-TATB. The reason is attributed to the difference in their structural features. Compared with H2BDC and H3BTC ligands in Bi-BDC and Bi-BTC, H3TATB ligands in the structure of Bi-TATB contained more delocalized π electrons. This outcome may facilitate the ligand-to-metal charge transfer (LMCT) and decrease the electronic bandgap of the Bi-TATB, thus contributing to the enhanced photocatalytic rate. The enhanced photocatalytic activity of Bi-TATB was further confirmed by the photodegradation of rhodamine B (RhB) under LED light irradiation, which is 99.1% of RhB removal after 180 min of light irradiation. The as-synthesized Bi-TATB showed promising photocatalytic activity for the degradation of organic dye with an excellent recyclable catalytic efficiency. With the above understanding, Bi-MOF was finally used for the photocatalytic O2 evolution from water under LED light irradiation. The Bi-TATB had a maximum photocatalytic O2 evolution rate of 691 μmol h−1. To the best of the author’s knowledge, there has been no research on both the photocatalytic degradation of organic model dye pollutants and photocatalytic O2 evolution studies using Bi-MOFs with different organic linkers. The results should open an alternative approach of ligand selection that could increase the applicability of Bi-MOF in the field of catalysis.