Room-temperature synthesis of a covalent organic framework with hydrazine linkages for sensitive fluorescent detecting and renewable removing of copper ions

A hydrazone bonded covalent organic framework (TFPB-DHzDs) was successfully synthesized with acetic acid as the catalyst and acetonitrile as the solvent at room temperature. It was proved that TFPB-DHzDs has good crystallinity and stability, as well as excellent luminescence properties. The solid-state absolute fluorescence quantum yield of TFPB-DHzDs was 6.19%. It is found that copper ions have a specific strong fluorescent quenching effect and can be absorbed by TFPB-DHzDs, which makes it possible for the selective sensing of copper ions. The TFPB-DHzDs COF exhibited excellent ability to determine Cu2+ in aqueous solution ranging from 0.1 to 5 μM with the detection limit of 47.8 nM. Furthermore, TFPB-DHzDs was also proved to be an excellent porous adsorbent for Cu2+ in water matrix and the maximum adsorption capacity is 203 mg g−1. The recycling use of TFPB-DHzDs for detecting and removing of Cu2+ can be easily realized by adding a chelating agent. And it can be recovered and recycled at least six times. This work explores the attractive potential of COF TFPB-DHzDs simultaneously as a sensitive fluorescent sensor and an efficient sorbent material, which broadens the application of COFs in fluorescence sensing, metal removal, and environmental analysis.