Effect of metal–ligand ratio on the rhodamine B photodegradation activity of metal-organic framework materials based on bismuth and trimesic acid

In this study, the photocatalytic degradation of rhodamine b (RhB) is investigated over metal-organic framework materials based on bismuth and trimesic acid (Bi-BTC) with different metal-to-ligand molar ratios. All obtained products are characterized by using powder X-ray diffraction, scanning electron microscopy, and UV–vis diffuse reflectance spectroscopy. It is found that decreasing the metal-to-ligand ratio below 1:1 produces high crystallinity and long rod-like crystals of Bi-BTC. For the metal-to-ligand molar ratios 5:1 and 1:1, we obtain low crystallinity of Bi-BTC. Additionally, a lower metal-to-ligand ratio in the Bi-BTC photocatalyst leads to the higher efficiency compared to other Bi-BTC photocatalysts. The metal-to-ligand ratio of 1:20 (Bi-BTC-0.05) favors the highest efficiency, in which 97.81% rhodamine B (RhB) is removed after 150 min of irradiation. The results should open a new approach to optimize the desired Bi-BTC structure for a target application.