Construction of naphthalene diimide-based cadmium complexes and their application in iodine adsorption, photochromism, and photocatalysis

Abstract

Two naphthalene diimide-based (NDI-based) complexes, [Cd(AlaNDI)(NH₂-BDC)_0.5(H₂O)]·(CH₃)₂NH₂ (1) and [Cd(AlaNDI)(BDC)_0.5(H₂O)]·(CH₃)₂NH₂·(CH₃)₂NH (2) (AlaNDI = N,N′-bis(L-alanine)naphthalenediimide, H₂BDC = terephthalic acid, NH₂–H₂BDC = 2-amino terephthalic acid), were successfully prepared under solvothermal conditions. The complexes were characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TG), X-ray powder diffraction (PXRD), and UV-vis absorption spectroscopy techniques. Structural analysis showed that the packing structures of the complexes were assembled with the subunit Cd₂(AlaNDI)₂ connected by BDC or NH₂-BDC moiety, forming an interspersed two-dimensional structure. In order to investigate the effect of uncoordinated amino groups in the complexes, structural comparisons and functional properties of iodine adsorption, photochromism, and photocatalysis were explored. Photocatalytic studies showed that both the complexes have good potential for photocatalytic degradation activity of various dyes, particularly for cationic dye crystal violet (CV), basic saffron (SFT), malachite green (MG), and methyl violet (MV). We found that the photocatalytic active species may be related to h⁺ and ˙OH.