Reconstruction of biomimetic ionic channels within covalent organic frameworks for ultrafast and selective uranyl capture

The efficient extraction of uranium, as the primary component of nuclear energy, holds significant implications. Drawing inspiration from the charge interaction observed in biological ion channels, we encapsulated negatively charged polystyrene sulfonate (PSS) or sodium polystyrene carboxylate (PVBA) into the nanochannels of amidoxime functionalized covalent organic framework (COF-AO) in-situ to alter the cavity environment of COF-AO. The synthesized COF-AO-PSS and COF-AO-PVBA are used for ultra-fast and highly selective uranium recovery. The negatively charged PSS/PVBA was confined in the COF-AO channel providing the driving force for uranium transport and blocking other ions, thus creating a highly selective "uranium highway". Additionally, introducing sulfonate groups or carboxyl groups into COF-AO offers supplementary coordination environments and weak interactions with uranium. Due to charge-assisted migration and various interaction mechanisms, both COF-AO-PSS and COF-AO-PVBA exhibit faster adsorption kinetics and higher selectivity compared to COF-AO alone. Their adsorption capacities are 3.8 times and 2.4 times that of COF-AO alone respectively which highlights the necessity for constructing biomimetic ion channels in uranium adsorption processes. This work presents a bionic adsorbent based on covalent organic frameworks (COFs) for the first time, overcoming environmental and equipment limitations associated with traditional photocatalysis and electrocatalysis methods for uranium capture, opening up new avenues for designing multifunctional materials that mimic biological systems.