Two new Co(II) coordination compounds, namely [Co(L)_0.5(DCDPE)]_n (1) and [Co(L)(npth)]_n·nH₂O (2) (L = 1,1′-(1,6-hexanediyl)bis[2-(2-pyridyl)benzimidazole], H₂DCDPE = 4,4′-dicarboxydiphenyl ether, H₂npth = 3-nitrophthalic acid), were hydrothermally prepared and characterized. 1 presents a 2D layered 3,4L83 network, while 2 exhibits a dinuclear structure. Both complexes possess high pH stabilities in the range from 3 to 12. 1 and 2 can serve as fluorescence probes to sense acetylacetone (acac), levofloxacin (LEV), and Ni²⁺ with high quenching constants and low detection limits. The fluorescence sensing mechanisms of 1 and 2 are discussed in detail.