Ultrastable Zirconium-Based Cationic Metal–Organic Frameworks for Perrhenate Removal from Wastewater
Guoyu Zhang, Kui Tan, Shikai Xian, Kai Xing, Hongbing Sun, Gene S. Hall, Liangying Li, Jing Li
Abstract
The effective removal of radioactive 99TcO4– anion from nuclear wastewater remains a very difficult unsolved problem. Functional adsorbent materials with high stability, anion-exchange capacity, excellent selectivity, and recyclability are much needed to solve this problem. In this work, we designed two stable cationic metal–organic frameworks (MOFs)—Zr-tcbp-Me and Zr-tcpp-Me—for possible use as adsorbent materials to remove 99TcO4–. Both compounds were synthesized by solvothermal reactions of the tetracarboxylate ligand with zirconium salt, followed by postsynthetic modification (N-methylation). The crystallinity of both zirconium-based MOFs can be well retained under harsh conditions, and they exhibit high adsorption capacity and selectivity toward ReO4– anion, a nonradioactive analogue of 99TcO4–. Zr-tcbp-Me and Zr-tcpp-Me demonstrate the highest framework stability toward acidity among all previously reported cationic MOFs that have been tested for perrhenate removal from wastewater.