Embedding High-Density Ionic Sites in Porous Aromatic Frameworks via Multivariate Strategy for ReO₄ ^- Capture

Rhenium is a rare and significant metal, making its recovery crucial for resource management. Herein, to address these issues, three porous aromatic frameworks with high-density ionic sites were successfully synthesized using a multivariate strategy. These MTV-iPAFs are named PAF-271, PAF-272 and PAF-273, respectively, and were employed for the ultrafast and selective removal of ReO₄ ^-. These materials exhibit varying high specific surface areas, porosities, and imidazolium densities. The results demonstrated that compared to PAF-272 with low adsorption site density and PAF-273 with high specific surface area, PAF-271 with higher imidazolium density exhibited superior performance for ReO₄ ^- adsorption. Specifically, PAF-271 could remove 98 % of ReO₄ ^- within 2 min, achieving a maximum adsorption capacity was 707 mg g^-1. Moreover, PAF-271 also had excellent stability, making it highly effective for ReO₄ ^- adsorption under strong acid or alkali, radiation, high anion concentration and even in Hanford simulated waste liquid, it is expected to be applied to adsorb TcO₄ ^-. Embedding high-density ionic sites within PAFs by multivariate strategy result in highly stable and effective ReO₄ ^- disposal approach.