Modulating Skeletons of Covalent Organic Framework for High‐Efficiency Gold Recovery

Abstract

Covalent organic frameworks (COFs) have attracted considerable attention as adsorbents for capturing and separating gold from electronic wastes. To enhance the binding capture efficiency, constructing hydrogen‐bond nanotraps along the pore walls was one of the most widely adopted approaches. However, the development of absorbing skeletons was ignored due to the weak binding ability of the gold salts (Au). Herein, we demonstrated skeleton engineering to construct highly efficiently absorbs for Au capture. The strong electronic donating feature of diarylamine units enhanced the electronic density of binding sites (imine‐linkage) and thus resulted in high capacities over 1750 mg g−1 for all three COFs. Moreover, the absorbing performance was further improved via the ionization of diarylamine units. The ionic COF achieved 90 % of the maximal adsorption capacity, 1.63 times of that from the charge‐neutral COF within ten minutes, and showed remarkable uptakes of 1834 mg g−1, exceptional selectivity (97.45 %) and cycling stability. The theoretical calculation revealed the binding sites altering from imine bonds to ionic amine sites after ionization of the frameworks, which enabled to bind the AuCl4− via coulomb force and contributed to enhanced absorbing kinetics. This work inspires us to design molecular/ionic capture based on COFs.

Alkadiyne–Pyrene Conjugated Frameworks with Surface Exclusion Effect for Ultrafast Seawater Desalination

“…Owing to the relatively higher concentration of Cu–pyridine near the support surface, the growth of PTEP preferentially occurred on the PCHF surface to form a well-covered membrane. Like the hydrothermal synthesis of supported microporous crystalline (e.g., zeolite) membranes, − the competitive growth of PTEP fragments in the synthesis solution can lead to precipitation and negatively affect the quality of the PTFP membrane (Figure S2). Therefore, the concentration of TEP in the synthesis solution is controlled to suppress the PTEP precipitation by slowly injecting TEP into the synthesis solution.…”

Dual-Crosslinking Polydopamine/Poly(imide dioxime) Porous Network Membrane Enables Efficient and Selective Gold Recovery from e-Waste

“…As a representative precious metal, beyond being used as jewelries, gold is extensively employed in electronics, medicine, and catalysis industries due to its robust corrosion resistance, excellent stability, superior electrical conductivity, and preferable thermal conductivity. − However, the surging emergence and accelerating renewal of electronic products render traditional mining routes insufficient to address the imbalance between the supply and demand for precious metal resources. Consequently, it is crucial to develop effective techniques for extracting gold from unconventional sources, such as electronic waste (e-waste), to supplement primary mining.…”