In this work, based on the conjugated structure of the naphthalene ring system, four stable Cd-NDI complexes {[Cd-o-H 2 BDC = phthalic acid; m-H 2 BDC = iso-phthalic acid; p-H 2 BDC = p-phthalic acid; H 3 TIBTC = 2,4,6-triiodo-1,3,5-benzene tricarboxylic acid) are designed and synthesized. The four Cd-NDI complexes have good luminescence properties, and complexes 1-3 can selectively detect Cr 2 O 7 2À and L-Arginine in water. Complex 1 has the best ability to detect Cr 2 O 7 2À with a limit of detection (LOD) of 2.32 μM; complex 3 can be employed for the detection of Larginine with a LOD of 2.25 μM. Complex 1-3 may be useful for monitoring water quality and treating wastewater as a good fluorescence sensor. In addition, based on the specific detection species of C=N bonds by complexes 1-3, we take complex 3 as an example to conduct preliminary studies monitoring a Schiff base reaction in situ with fluorescence quenching. This provides a new method for monitoring organic reactions. Besides, we also have explored the ability of complex 4 to detect pnitroaniline. The results show that the complex 4 could selectively detect p-nitroaniline with a LOD of 5.12 μM.