Impact of nitro and amino functional groups on the intercalation of isophthalic acid in ZnAl layered double hydroxides: An experimental and theoretical study

This study explores the effects of nitro (–NO 2 ) and amino (–NH 2 ) functional groups on the intercalation of isophthalic acid (IPA) into ZnAl layered double hydroxide (LDH) through experimental and theoretical approaches. ZnAl LDHs intercalated with IPA, 5-aminoisophthalic acid (AIPA) and 5-nitroisophthalic acid (NIPA) were synthesized via the co-precipitation method. Experimental results revealed different ion-exchange behavior reflected on loading and release properties. UV–Vis analysis determined the loading capacity sequence as NIPA ​≥ ​AIPA ​> ​IPA, while release kinetics in NaCl solution followed AIPA ​> ​IPA ​> ​NIPA. Density functional theory (DFT) simulations highlighted deprotonated carboxylic groups on the benzene rings as primary binding sites, and the affinity of species to the interlayers was estimated as NIPA 2− ​> ​AIPA 2− ​> ​IPA 2− . The interlayer arrangements are proposed considering the interlayer distances, interaction sites, surface area per charge, density deviations and patterns of intercalates in its natural crystal structures. The results reveal that the functional groups significantly influence the interlayer structure of species in the LDH. The addition of –NO 2 group stabilizes the species via interaction with hydroxide layers, while the –NH 2 renders AIPA less stable in the interlayer due to its electron accepting nature which containing two positively charged hydrogen atoms.