Ratiometric fluorescent sensing of copper (II) by a new covalent organic framework-based platform

Although copper is essential for various functions in the human body, excessive intake can damage the nervous and immune systems. In this study, a new fluorescent covalent organic framework probe (DP-TFPB COF) was first reported. Relying on the rational design, the synthesized DP-TFPB COF demonstrates a distinctive fluorescence enhancement effect upon different solvent induction, achieving a quantum yield of up to 20.5 %. Then, a covalent organic framework-based ratiometric fluorescent system was developed, incorporating blue-emitting carbon dots to leverage the fluorescence energy transfer effect. Blue-emitting carbon dots served as the reference signal, while the DP-TFPB COF acted as the response unit, enabling successful quantitative detection of Cu²⁺. The mechanism study demonstrated that fluorescence quenching occurs through an electron transfer process, wherein the covalent organic framework serves as the electron donor and Cu²⁺ functions as the electron acceptor. The developed method demonstrated excellent linearity for Cu²⁺ within the concentration range of 0.5 to 200 μM, accompanied by a detection limit of 0.38 μM. The robust recognition capabilities exhibited significant effectiveness in the Cu²⁺ analysis within herbal plants. The results correspond closely with those obtained using inductively coupled plasma mass spectrometry, thereby emphasizing its potential applicability in real samples with complex matrix.