Tuning electronic structure of the carbon skeleton to accelerate electron transfer for promoting the capture of gold

The efficient and selective recovery of gold from secondary sources is key to sustainable development. However, the complexity of the recovery environment can significantly complicate the compositions of utilized sorbents. Here, we report a straw-derived mesoporous carbon as an inexpensive support material. This mesoporous carbon is modified by anions (sulfur modulation, C-S-180) to improve its electron-transfer efficiency and tune the electronic structure of its skeleton toward enhanced gold reduction. The high surface area of C-S-180 (989.4 m²/g), as well as the presence of abundant C-S in the porous structure of the adsorbent, resulted in an outstanding Au³⁺-uptake capacity (3422.75 mg/g), excellent resistance to interference, and favorable Au³⁺ selectivity. Dissimilar to most existing carbon-based adsorbents, electrochemistry-based studies on the electron-transfer efficiencies of adsorbents reveal that sulfur modulation is crucial to optimizing their adsorption performances. Furthermore, the density functional theory reveals that the optimization mechanism is attributable to the adjustment of the electronic structure of the carbon skeleton by C-S, which optimizes the band-gap energy for enhanced Au³⁺ reduction. These findings offer a strategy for constructing green and efficient adsorbents, as well as a basis for extending the applications of inexpensive carbon materials in gold recovery from complex environments.