A novel coordination polymer (CP) {[Cd₂(L)(1,4-bimb)_1.5(DMF)₂]·DMF}_n (1) (H₄L=5, 5′-[1,1′-biphenyl-4,4′-diylbis(oxy)]diisophthalic acid, 1,4-bimb=1,4-bis(imidazole-1-ylmethyl)-benzene) has been designed and synthesized through solvothermal reaction. Structural analysis shows that Cd(Ⅱ) is connected by H₄L and 1,4-bimb to form a 2D network, and 1,4-bimb further expands the 2D network into a 3D framework. CP 1 can be used as an excellent fluorescence sensor for Fe³⁺ and 4-nitrophenol (4-NP), with low detection limits and good anti-interference. The detection limits of Fe³⁺ and 4-NP were 0.034 and 0.031 μmol·L^-1, respectively. In addition, the fluorescence quenching mechanism was studied. 1 was successfully applied to determine Fe³⁺ and 4-NP content in the Yanhe River water sample.