A sulfhydryl-functionalized vinylene-linked covalent organic framework for promoting gold recovery by light-assistance.

A sulfhydryl-functionalized vinylene-linked covalent organic framework (viCOF-mtd) has been successfully synthesized and possesses excellent performance for gold recovery with light-assistance. [Display omitted] • A vinylene-linked viCOF-mtd with sulfhydryl groups shows excellent performance for gold recovery. • The vinyl groups endow viCOF-mtd with a highly conjugated structure and good photoelectrical properties. • viCOF-mtd has a twofold higher adsorption capacity for gold with light assistance. • The gold adsorption of viCOF-mtd is accomplished by electrostatic interaction, S–Au coordination, and redox effect. Gold, as one of the precious metals, has a wide range of applications and a high market demand. Recovering gold from secondary resources not only safeguards the natural environment but also optimizes resource utilization. Extensive efforts have been devoted to developing materials that can efficiently and selectively recover gold from solutions via adsorption in a rapid manner. In this study, we designed and prepared a vinylene-linked covalent organic framework (viCOF-mtd) through post-synthesis modification by sulfhydryl groups for efficient recovery of gold in aqueous solution. viCOF-mtd exhibits good porosity and structural stability, and possesses an attractive gold adsorption capacity up to 1249 mg g−1. By introducing light stimulation, the gold adsorption capacity of viCOF-mtd can be further enhanced to 3386 mg g−1 along with improved adsorption kinetics. The results of various structural and property characterization tests and density-functional theory (DFT) calculations confirm the presence of electrostatic interaction, S–Au coordination, and redox effects during the gold adsorption process. Notably, light stimulation can effectively increase the photogenerated electrons in viCOF-mtd, which enhance the redox effect on gold ions. Furthermore, viCOF-mtd exhibits remarkable adsorption selectivity towards gold even in the solutions with multiple competing ions and in the complex seawater system. [ABSTRACT FROM AUTHOR]