Preparation of porous organic polymers via alternating radical copolymerization for uranium adsorption

Meriting from the unique affinity of amidoxime groups towards uranium ions, porous organic polymers (POPs) substituted with cyano groups are promising precursors as high-performance uranium adsorbents. However, their synthesis suffers from harsh conditions, tedious operations, or costly catalysts, which hamper their large-scale utilization. Free-radical alternating copolymerization strategy offers a simple and viable approach to circumvent these bottlenecks with great atomic economy. Here, two electron-withdrawing cyano monomers, acrylonitrile (AN) and fumaronitrile (FN), are successfully integrated with the electron-rich divinylbiphenyl (DVBP) monomer via free-radical alternating copolymerization strategy, forming two family of POPs with tailorable cyano contents. After post-amidoximation, two types of amidoxime-functionalized POPs (AO-POPs) are consequently obtained. Having probed the cyano-induced penultimate effect, it is observed that different feed ratios has regulated the polymerization behaviors, porosities and even adsorption capacities of AO-POPs. Among them, AO-POPs-FN-3, with an appropriate specific surface area and the highest amidoxime content, exhibits the best uranium adsorption capacity (723 mg g⁻¹), along with good selectivity and regenerability. This work demonstrates an environmentally friendly and easy-to-operate free radical copolymerization strategy for the rational design of POPs-based adsorbents and paving for the recycling and sustainable development of uranium resources.