An ultrastable cationic covalent organic framework for selective capture of silver from aqueous solution

Recovery of silver from wastewater is a promising alternative from the economic and environmental perspective. Herein, we present an ultrastable ionic covalent organic framework (COF) as a recyclable adsorbent for Ag(I) recovery. The COF exhibits a large surface area, regular pores, and extremely high chemical stability combined with the confined ionic interface, which makes it an excellent material for silver adsorption with fast adsorption kinetics, excellent selectivity, and high saturated adsorption capacity (up to 349.6 mg/g). The superb uptake performance of the cationic COF is attributed to the in-situ precipitation of AgBr and adsorption as well as the coordination of O atoms on the framework to silver.