Alkyne-Based Covalent Organic Frameworks for Highly Selective Capture of Trace Gold from Aqueous Solutions and Electronic Waste

The recovery of gold from electronic waste and industrial leachates has attracted great interest. However, developing highly efficient and selective adsorbents for capturing trace gold remains a challenge. Herein, an alkyne-based covalent organic framework (TAPB-BPTA COF) was synthesized at room temperature and employed for Au(III) capture for the first time. The introduction of alkyne groups onto TAPB-BPTA COFs endowed it with an ultrahigh adsorption capacity of up to 2311.9 mg g –1 (calculated maximum adsorption capacity) toward Au(III), which was 4-fold higher than that of the counterpart COFs without alkyne groups. Furthermore, the TAPB-BPTA COFs showed high selectivity, fast adsorption kinetics, and excellent regeneration ability. Characterizations and calculations revealed that the synergistic effect of imine bonds and alkyne groups in TAPB-BPTA COFs played a crucial role in promoting Au(III) capture. Encouraged by the superior performance, the TAPB-BPTA COFs were further applied to capture trace Au(III) in aqueous solutions and electronic waste. The results demonstrated that high extraction efficiencies for Au(III) were achieved all above 93.6%. In addition, the selectivity for Au(III) was characterized by partition coefficients ( K d ), and the K d was 65,810.3 mL g –1 of TAPB-BPTA COFs for Au(III) in the leachates of CPUs, approximately 15,000 and 1000 times higher than those of Ni(II) and Cu(II), respectively. This work not only expands the application of COFs in separation science but also provides a promising strategy to capture trace Au(III) from complex samples.