Functional covalent organic framework illuminate rapid and efficient capture of Cu (II) and reutilization to reduce fire hazards of epoxy resin

Abstract

A key challenge for decontamination technologies is to study adsorbents possessing abundant approachable binding sites to realize rapid and effective capture of heavy metal ions in contaminated water. Herein, a three-dimensional porous covalent organic framework (COF) was synthesized, which can function as a scaffold for decorative binding sites. Considering the plentiful functional groups such as catechol groups of polydopamine (PDA), the decoration is demonstrated by coating PDA on the surface of COF via self-polymerization of dopamine under alkaline conditions. The obtained PDA-coated COF (COF@PDA) shows high affinity for copper ions (Cu (II)), while its adsorption capacity reaches 109.2 mg g−1 according to the Langmuir fitting. It takes only 10 min to achieve adsorption equilibrium and its equilibrium data follows pseudo-second-order kinetic model. Thermodynamic studies confirmed a spontaneous and exothermic removal process in essence. To achieve cyclic utilization of Cu (II), the adsorbed Cu (II) ions were heat-treated into CuO to obtain CuO-loaded COF@PDA (COF@PDA@CuO). It can serve as flame retardant for reducing fire hazards (heat, smoke and toxic gas) of epoxy resin (EP), thus confirming its dual functionalities towards environmental remediation and application as flame-retardant.