Dual-Bridged Porphyrin-Based Covalent Organic Framework with Integrated Specific Fluorescent Recognition and Cooperative Adsorption Capabilities

Developing candidate materials with specific recognition and efficient adsorption is highly valuable for both the environment and ecology. Covalent organic frameworks (COFs) are an ideal multifunctional candidate material due to their structure, functional modification, and excellent physical and chemical properties. However, most COF monomers can coordinate with various metal ions, thus limiting their application in accurate identification. Herein, we designed a double-bridged porphyrin-based covalent organic framework (Tp-PDA-COF) by introducing double-bridging monomers to orderly connect the 5,10,15,20-tetra(4-aminophenyl)porphyrin (TAPP) center to construct the 2D tetragonal topological structure with an excellent fluorescence property. The designed topology effectively reduces spatial hindrance, and the specific electron cloud density can optimize metal ligand orbitals, achieving effective capture and specific coordination recognition, which achieves sensitive detection of Cu2+ through obvious fluorescence chromaticity change with a detection limit of 40.76 nM. Furthermore, incorporating poly(vinyl alcohol) polymer into the COF increases interlayer spacing and suppresses π-π stacking, forming a fluorescent Tp-PDA-COF aerogel. Owing to the selective coordination of Cu2+ and the synergistic adsorption of gel structure, Tp-PDA-COF aerogel has an ultrahigh adsorption capacity for Cu2+ (1902 mg/g). This work provides a structural design strategy for regulating functional COFs with specific recognition and adsorption capabilities.