A unique multi-functional cationic luminescent metal–organic nanotube for highly sensitive detection of dichromate and selective high capacity adsorption of Congo red

Abstract

In this work a flexible multi-dentate 1-(4-aminobenzyl)-1,2,4-triazole (abtz) ligand has been employed, a unique cationic triazole–Ag(I) metal–organic nanotube {[Ag(μ₃-abtz)]·(NO₃)·(0.125H₂O)}_n (MONT-1) has been isolated under solvo-thermal conditions. The abtz ligands adopt tri-dentate coordination modes via triazole nitrogen atoms and aromatic amino nitrogen atoms, which bridge neighboring Ag^I centers in a syn conformation, leading to MONT formation. PXRD patterns have been investigated indicating pure phases of MONT-1. Solid-state luminescence properties indicate strong fluorescent emissions of MONT-1 at room temperature. Further, interestingly MONT-1 exhibits visually highly selective and sensitive luminescence sensing for Cr₂O₇²⁻ ions in aqueous solutions with high quenching efficiency K_sv = 1.97 × 10⁴ L mol⁻¹ and low detection limit (0.19 μM (S/N = 3)), which make it a promising candidate for visually sensing Cr₂O₇²⁻ anion pollutants in practice. On the other hand, the absorption of environmental pollutants by MONT-1 has also been investigated. MONT-1 has a high absorption capacity for Cr₂O₇²⁻ (211.8 mg g⁻¹), and these absorbed Cr₂O₇²⁻ anion pollutants can be gradually released in the presence of nitrate. Additionally MONT-1 also can selectively adsorb Congo Red (CR) dye molecules in aqueous solutions with a high absorption capacity of 823.3 mg g⁻¹. Therefore MONT-1 can be used a unique multi-functional 1D nano-tubular metal–organic material in sensitive detection and effective adsorption/removal of these environment pollutants in industrial waste water solutions.