In this work, a Bi-based metal-organic framework (MOF; Bi-MMTAA) with 2-mercapto-4-methyl-5-thiazoleacetic acid (MMTAA) as the organic ligand is synthesized. The crystal structure of Bi-MMTAA was determined by single-crystal X-ray diffraction. Theoretical calculations reveal that Bi-MMTAA is a p-type semiconductor, and electrons can delocalize through the π-conjugation when excited by a photon with an energy higher than the Bi-MMTAA band gap, which is beneficial to charge separation and transfer. The photoelectrical properties suggest that free electrons can be produced over Bi-MMTAA under light irradiation. The photocatalytic results suggest that Bi-MMTAA can decolorize rhodamine B (RhB) and oxidize phenylboronic acid to phenol under visible light (λ > 420 nm), with superoxide radicals being the main reactive oxygen species. Our results enrich the family of Bi-based MOFs and may inspire further exploration of Bi-based MOFs, including both synthesis and potential applications.