Amide-based covalent organic frameworks materials for efficient and recyclable removal of heavy metal lead (II)

Abstract

Abstract Covalent organic frameworks (COFs) materials with designed skeleton structure and controlled pore size are a new class of adsorbent materials for environment remediation. Here, we synthesize two amide-based COFs materials via a polymerization reaction of acyl chloride and amino groups by mechanical ball milling at room temperature for Pb2+ removal as adsorbents. Two types of diamine monomers are selected to construct COFs with different framework structure and functional groups contents, i.e. COF-TP from aromatic diamine and COF-TE from linear diamine. The as-prepared COFs materials display typical lamellar structure, and the amide groups on COFs skeleton are confirmed to behave as active adsorption sites for Pb2+ capture via multi-coordination. COF-TE exhibits superior Pb2+ adsorption capacity to COF-TP, because that less aromatic skeleton and weak π-π stacking of COF-TE facilitate higher internal diffusion of Pb2+ adsorption. Meanwhile, the higher amide group content on COF-TE leads to its higher saturated adsorption capacity of 185.7\u202fmg/g than COF-TP of 140.0\u202fmg/g. Finally, great recycling stability of Pb2+adsorption allows the amide-based COFs materials to be promising adsorbents for heavy metal Pb2+ removal or recovery.