Design and synthesis of 2D coordination polymers from isophthalic and adipic acids: exploring Tb-based luminescent sensors for Cr3+, Fe3+ and p-NA†

Abstract

In this study, we focus on the design and synthesis of nine isoreticular coordination polymers under solvothermal conditions by incorporating lanthanide ions (Ln) through a dual ligand strategy using isophthalic acid (H₂Ita) and adipic acid (H₂Adip) with the general formula [Ln(Ita)(Adip)_0.5(H₂O)₂]_n. Structural analysis indicates that all synthesized CPs crystallize in the triclinic P space group. All of the CPs are isostructural and isomorphous with a distorted tricapped trigonal prismatic geometry around the lanthanide metal centre. CP 7 exhibits the signature luminescence property of Tb³⁺ and is explored for its potential in sensing metal (Fe³⁺ and Cr³⁺) ions and p-nitroaniline (p-NA). Luminescence titration experiments revealed turn-off sensing ability of CP 7 towards Fe³⁺ ions and turn-on sensing towards Cr³⁺ ions. The sensing mechanisms involve competitive energy absorption and weak interactions between the metal ions and the CP framework. Furthermore, CP 7 demonstrates remarkable selectivity and sensitivity towards Cr³⁺, Fe³⁺ and p-NA, with quick response times and excellent recyclability. Additionally, EDTA was found to restore the luminescence of CP 7 in the presence of Fe³⁺ ions, demonstrating its potential for detecting EDTA. Overall, our study demonstrates the promising application of CP 7 as a luminescent sensor for the environmental monitoring of metal ions and NACs.