Bottom-up synthesis of cationic porphyrin-based porous organic polymers for highly efficient and selective recovery of gold

Developing ionic porous organic polymers (i-POPs) to retrieve gold from electronic waste is still in its infancy. Herein, for the first time, a cationic imidazolium and porphyrin cross-linked POPs, Imi-PPOPs-Br, was constructed by combining pyrrole and imidazolium-functionalized trialdehydes via the bottom-up method. As expected, the introduction of cationic imidazolium and porphyrin rings has endowed material high adsorption capacity (1543 mg/g), preferable reusability (more than eight times), and specific selectivity to Au (III). Multiple characterization results and density functional theory (DFT) calculations revealed that the adsorption mechanism of Au (III) by Imi-PPOPs-Br could be due to the electrostatic interaction between cationic Imi-PPOPs-Br and AuCl4− anions, strong bind of Au and N active sites, and reductive immobilization of Au (III) to Au (0). This study may put forward a new and facile strategy for constructing stable i-POPs that can be used as desirable absorbents in environmental fields.