Acid-resisting covalent organic framework enabling high-efficiency palladium recovery from used palladium catalyst under strong acid

Abstract

Pd recovery from used sources is now receiving growing attentions, due to its scarcity and important application in many fields, however, which is still seriously restricted by the lack available adsorbent that can effectively capture palladium (Pd) from strong acid (>3 M). To this end, we report herein an acid-resisting covalent organic framework (COF), namely ECUT-COF-20, for such use. This new adsorbent is found to perform a benchmark Pd recovery performance from 6 M acidity such as the fast adsorption kinetics (1 min) and high uptake capacity (181 mg/g). The breakthrough test from a Pd/C-digested solution is used to confirm its practical application, giving an exceptionally one-round 95 % Pd recovery efficiency. The mechanism, as unveiled by characterization and DFT calculation, is due to a spatial and functional separation in this adsorbent, which could consequently not only overcome the influence of strong acid, but also provide abundant hydrogen bonds for fixing Pd ions.