| May 05, 2026 |
Researchers developed a photocatalytic covalent organic framework that selectively captures gold from electronic waste leachate with 99% efficiency and strong reusability.
(Nanowerk News) A two-dimensional covalent organic framework (COF) can selectively recover gold from electronic waste solutions with roughly 99% efficiency, according to research published in the journal Research (“Electronic Structure Tailored Covalent Organic Frameworks for Synergistic Adsorptive–Photocatalytic Gold Recovery from Complex Electronic Waste”).
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The material, developed at Hainan University, combines light-driven catalysis with molecular-level adsorption through carefully tuned donor–acceptor interactions and p–π conjugation effects. In tests on real CPU board leachate, it captured about 99.9% of the gold within four hours under light irradiation.
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Key Findings
- The new COF material recovers approximately 99% of gold from simulated electronic waste and about 99.9% from real CPU board leachate in four hours.
- The framework maintains over 99% recovery efficiency after four consecutive reuse cycles.
- Methoxy group modifications enhance gold selectivity even in the presence of high concentrations of competing metals such as copper and nickel.
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The team constructed the COF, designated TAPP-TZ-OMe-COF, using a Schiff base reaction. COFs are porous crystalline materials built from organic molecules linked by strong covalent bonds in repeating patterns, and their modular architecture allows researchers to incorporate specific functional groups and tune electronic properties at the molecular level.
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In this design, the researchers strategically incorporated thiazole units and methoxy groups to create abundant binding sites optimized for gold capture while also engineering favorable light-absorbing properties for photocatalytic reduction.
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| Schematic of the strategy to boost gold recovery performance of COFs. (A) Schematic for boosting gold recovery efficiency by optimizing the electronic structure and increasing gold binding sites in COFs. (B) Synthesis of COFs with modulated structural characteristics to enhance gold recovery efficiency. (Image: Reproduced from DOI:10.34133/research.1012, CC BY)
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Photocatalysis drives the recovery process by using light energy to convert soluble gold(III) ions into insoluble metallic gold, which can then be physically collected. This approach requires less energy than conventional hydrometallurgical or pyrometallurgical methods and avoids many of their environmental drawbacks.
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Gold concentration in electronic waste runs 80 to 100 times higher than in natural ores, and global e-waste was estimated to contain 1,568 tons of gold by 2025, with total electronic waste volumes projected to reach 74.7 million tons by 2030.
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“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 corresponding author and a professor at Hainan University’s School of Marine Sciences. “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.”
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The material’s selectivity depends on a deliberate electronic structure modification. The methoxy groups boost the electron density around the thiazole units, making the sulfur and oxygen atoms more electron-rich. These enriched sites preferentially bind with gold(III) ions because gold(III) acts as a soft acid in coordination chemistry, meaning it favors bonding with soft, electron-donating atoms like sulfur and oxygen over harder metal ions.
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This chemical preference allows the COF to capture gold even when competing metals like copper and nickel are present at far higher concentrations, as is typical in real e-waste leachates.
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Testing in both simulated and real-world conditions confirmed practical viability. In simulated electronic waste solutions containing multiple metal ions, the COF showed pronounced selectivity for gold over other elements. When applied to actual CPU board leachate containing a complex mixture of dissolved metals, the material recovered about 99.9% of the gold within four hours under light irradiation. Reusability tests showed that the COF retained more than 99% of its recovery capacity through four consecutive adsorption–recovery cycles.
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“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,” said Professor Wang. “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.”
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Gold plays essential roles across electronics, catalysis, biomedicine, and aerospace because of its chemical stability and unique physical characteristics. As the electronics industry expands, the growing volume of discarded devices represents both an environmental burden and a substantial untapped resource. Developing materials that can extract precious metals efficiently and selectively from these complex waste streams could reduce dependence on conventional mining while addressing e-waste pollution.
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“Incorporating photocatalytic functional groups into adsorbent materials for gold recovery from electronic waste represents an important direction for future research and technological development,” Professor 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.”
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