The newly designed two-dimensional COF features abundant adsorption sites and favorable photoelectronic properties, exhibiting high selectivity toward gold in electronic waste.

Gold (Au) is a precious metal resource that plays an important role in the global financial system. Attributied to its unique physical properties and chemical stability, gold has also been widely utilized for various practical applications, including electronic communication, catalysis, biomedicine, and aerospace. With the rapid development of the electronic industry, the accumulation of global electronic wastes is increasing substantially, and its total amount is predicted to reach 74.7 million tons by 2030. It is notable that the concentration of gold in these electronic wastes is approximately 80 to 100 times that in natural gold ores, and the global electronic waste is estimated to contain 1,568 tons of gold by 2025, representing a vast underutilized resource. Notably, photocatalysis, which reduces soluble Au(III) to insoluble Au(0), is considered a sustainable and efficient strategy for gold recovery due to its low energy consumption, high efficiency, and environmental friendliness.

Now, a research team at Hainan University has developed an electronically structured covalent organic framework regulated by donor–acceptor interactions and p–π conjugation, enabling highly efficient gold recovery from CPU board leachate. The framework exhibits excellent gold recovery performance in simulated electronic waste solutions, achieving approximately 99% gold recovery. In real CPU board leachate, the material recovers about 99.9% of gold within 4 h under light irradiation.
“The sustainable extraction of gold from electronic waste is not only critical for meeting growing global demand but also essential for mitigating the ecological risks associated with e-waste pollution,” said Ning Wang, the correspondence author of this study. “Innovative materials can advance this field by enhancing the selectivity and recovery efficiency for gold. Our work demonstrates an effective strategy for optimizing gold recovery performance of COF photocatalysts through electronic structure regulation and increased binding sites, and presents a promising material for gold recovery from electronic waste.”

Wang is a professor in School of Marine Sciences, State Key Laboratory of Marine Resource Utilization in South China Sea, Hainan University.

COF materials for gold recovery
Covalent organic frameworks (COFs), owing to their structurally tunable architectures, represent ideal platforms for the rational design of functional photocatalysts. Incorporating electron donor and acceptor units into COFs has emerged as an effective strategy to modulate their photocatalytic properties, facilitating efficient separation of photogenerated electron hole pairs and suppressing charge recombination, thereby enhancing photocatalytic performance. In this study, a novel two dimensional COF was constructed via a Schiff base reaction for efficient gold recovery from electronic waste. By introducing abundant gold binding sites and optimizing the electronic structure through donor acceptor interactions and p–π conjugation effects, the resulting COF exhibits high gold recovery efficiency under photocatalytic conditions.

Selective recovery of gold
The results show that TAPP-TZ-OMe-COF exhibits an exceptionally high recovery capability toward gold (Au(III)) under light irradiation. The material also demonstrates excellent reusability, retaining more than 99% of its recovery efficiency after four consecutive cycles. In addition, TAPP-TZ-OMe-COF achieves similarly high gold recovery performance in real electronic waste systems. The material displays good selective recovery of gold ions in simulated electronic waste solutions and pronounced selectivity toward gold ions in real electronic waste. This selectivity is mainly attributed to the synergistic effect of the tailored adsorption sites. Specifically, the methoxy groups enhance the electron density of the thiazole units, rendering the sulfur and oxygen atoms softer and more electron rich, thereby promoting binding between the adsorption sites and the soft acid Au(III) centers.
“The extraction of gold from electronic waste resources, as well as the mitigation of electronic waste pollution, requires a comprehensive and in depth understanding of the associated chemical and environmental processes,” said Professor Ning Wang. “Electronic waste contains large amounts of competing metal elements, including copper and nickel, whose concentrations are far higher than that of gold and severely interfere with gold recovery. These challenges highlight the necessity of developing highly selective and efficient extraction methods, which are essential for achieving sustainable gold recovery and the sustained mitigation of electronic waste pollution.”

Next Steps
“Incorporating photocatalytic functional groups into adsorbent materials for gold recovery from electronic waste represents an important direction for future research and technological development,” Professor Ning Wang added. “By introducing catalytic sites specifically targeting gold into the adsorbents, such advanced materials are expected to promote the transformation of gold species, thereby further improving the efficiency of gold extraction from electronic waste.”

The complete study is accessible via DOI:10.34133/research.1012