Under solvothermal conditions, using Cd(NO₃)₂·4H₂O as the metal source, pentamethylisophthalic acid (H₂MIP) ligand and 1, 3-bis (2-methyl-1H-imidazol-1-yl) propane (BMIP) as mixed ligands, a novel Cd(Ⅱ) organic framework material {[Cd(MIP)(BMIP)]·2/3DMF}_n (SNUT-47) was constructed. X-ray single-crystal diffraction indicates that SNUT-47 exhibits a two-dimensional bilayer organic framework structure. The obtained complex was further characterized by powder X-ray diffraction, infrared spectroscopy, thermogravimetric analysis and other techniques. The positions of the experimental and simulated diffraction peaks match well, indicating that the synthesized SNUT-47 material has excellent phase purity and reproducibility. Fluorescence experiments show that SNUT-47 possesses excellent fluorescence properties and exhibits a significant fluorescence enhancement effect for Na⁺ in aqueous solution, making it an efficient fluorescent sensor for the detection of Na⁺ with a detection limit of 2.56×10^-6 mol/L. Additionally, SNUT-47 can be easily recycled after cyclic experiments with just water washing, demonstrating good recyclability.