Facile construction of phenolic hydroxyl anchored covalent organic frameworks/chitosan composite aerogels for efficient adsorption of Pb (II) from water

Covalent organic frameworks (COFs) are proven ideal porous materials for adsorptive removal of heavy metals from water, while their external powdery form makes them difficult to separate and inconvenient to operate in the adsorption process, and integrating them to other substrates to form the macroscopic monolithic materials is a good alternative. Herein, the phenolic hydroxyl anchored COFs powders (COFs-OH) were synthesized and integrated into the chitosan gels to facilely construct the COFs-OH/chitosan composite aerogels, which not only realized the fast solid-liquid separation, but also rapidly adsorbed Pb (II) from water compared to the pure chitosan and COFs-OH powders. In particular, regulating the pore environments by adjusting the numbers of the phenolic hydroxyl for the COFs-OH precisely controlled the adsorption of Pb (II). The maximum capacity on the resulting aerogels, namely, DHTA-Pa/CS, was up to 1268 mg/g, and the adsorption reached the equilibrium within 15 min. The adsorption mechanism revealed that the N-/O-containing active sites of the COFs and chitosan had synergistic effect. This study provides a new idea for the facile construction of new porous composite materials for the efficient and fast adsorption of Pb (II) from water.