Construction and ReO4− adsorption of ionic covalent organic frameworks by solvothermal synthesis based on Zincke reaction

Rhenium is one of the highly scarce and important metals, and its capture is significant for resource recovery. As the latest generation ion exchange materials, ionic covalent organic frameworks (iCOFs) are desired for the acquisition of Re with large adsorption capacity, excellent selectivity, high stability and well-defined pore structures yet seldom reported. In this paper, two highly ordered iCOFs (TABD-COF and TAPB-COF) are successfully constructed via Zincke reaction by the common solvothermal synthesis. In particular, the morphology and crystallinity of iCOFs can be tuned by adjusting the reaction conditions and the structures of precursors. The analysis of PXRD, SEM, and TEM confirms that the two iCOFs exhibit highly ordered crystalline structures with multilayer stacking. TABD-COF and TAPB-COF perform relatively good thermally stability and high chemical stability in both acidic and basic conditions. Both of the two iCOFs show excellent adsorption performance for aqueous ReO4− (714 mg g−1 for TABD-COF, 633 mg g−1 for TAPB-COF) and fast ion exchange kinetics, in which 98 % of ReO4− are captured within 3 mins and 5 mins. Moreover, they also have outstanding trapping efficiency of ReO4− at excesses of competing anions. This work broadens the synthesis of iCOFs via Zincke reaction and provides two novel iCOFs for efficient capture of ReO4− in complex systems.