We synthesized metal-organic framework materials based on bismuth and trimesic acid (Bi-BTC) by the solvothermal method using a mixed solvent of N,N-dimethylformamide (DMF) and methanol (MeOH) at different volume ratios. The results have shown that the presence of MeOH ensured the effective Bi-BTC formation in the DMF environment, meaning that the pure DMF environment was inactive for Bi-BTC formation. The properties of Bi-BTC, such as size and porosity, varied in response to the change of synthetic solvent, resulting in a difference in the photocatalytic properties of the material. The change in the material structure under the influence of different solvents leads to a change in light absorption properties and thus affects their photocatalytic mechanism. Our study contributes a new insight to improve the photocatalytic activity of Bi-BTC.