An amide-linked pyrene-based imine COF for high-performance gold recovery from e-waste

This report presents the first application of an amide linkage strategy in pyrene-based imine COFs. • Amide groups enhance the polarity and coordination ability of TFPPY-DA-COF channels. • The TFPPY-DA-COF achieved an Au adsorption capacity of 2040 mg g −1 . Pyrene-based covalent organic frameworks (COFs) have received considerable attention for gold recovery, yet challenges remain in terms of adsorption capacity and economic cost. Herein, we initially employed an amide linkage strategy to construct a pyrene-based imine COF for gold recovery. The introduction of amide groups enhanced the polarity and coordination ability of the pore walls, enabling amide-linked COF to exhibit an Au uptake of 2040 mg g −1 , which is approximately twice that of its non-amide counterpart, and superior to most previously reported pyrene-based COFs. Moreover amide-linked COF also demonstrates excellent selectivity (distribution coefficient for Au exceeding 2.74 × 10 5 ; maximum separation factor > 6000) and outstanding performance in practical applications. Notably, the ligands used to synthesize both pyrene-based COFs are low-cost, and the captured Au particles can reach micrometer-scale sizes, which facilitates their separation and recovery. Further performance tests, combined with characterization and DFT calculations, reveal that the coordination of Au ions by the carbonyl groups in the amide linkages plays a dominant role during adsorption, and the reduction effect of the protonated imine bonds also contributes to improving the adsorption performance. Overall, this work provides a new approach for using COF materials to selectively capture and recover gold, offering potential for practical applications. Download: Download high-res image (141KB) Download: Download full-size image