Functional decoration on a regenerable bifunctional porous covalent organic framework probe for rapid detection and adsorption of copper ions

Abstract

Developing fluorescence porous probe for detecting and eliminating Cu²⁺ contamination in water or biosystem is an essential research project that has attracted considerable attention. However, improving the fluorescence detecting efficiency while enhancing the adsorption capacity of the porous probe is of great challenge. Herein, a bifunctional two-dimensional imine-based porous covalent organic framework (TTP-COF) probe was designed and synthesized from 1,3,5-tris (4-aminophenyl) benzene (TAPB) and 2,4,6-Triformylphloroglucinol (TP) ligand. TTP-COF displayed rapid detection of Cu²⁺ (limit of detection (LOD) = 10 nmol·L⁻¹ while achieving a high adsorption capacity of 214 mg·g⁻¹ (pH = 6) at room temperature with high reusability (> 5 cycles). The key roles and contributions of high π-conjugate and delocalized electrons in TABP and functional –OH groups in TP were proved. More importantly, the fluorescence quenching mechanism of TTP-COF was studied by density functional theory theoretical calculations, revealing the crucial role of intramolecular hydrogen bonds among C=N and –OH groups and the blocking of the excited state intramolecular proton transfer process in detecting process of Cu²⁺.