Enhanced selective adsorption of NSAIDs by covalent organic frameworks via functional group tuning

A suitable porous adsorbent with prominent adsorption performance and better selectivity for the target containments such as non-steroidal anti-inflammatory drugs (NSAIDs) is highly desired in wastewater treatment. Owing to the intrinsic attributes known as predictable structure, tunable pore size, high chemical stability as well as the reliable post-synthetic modification, covalent organic frameworks (COFs) are considered as brilliant adsorbent candidates which have drawn great attentions. Herein, two COFs with different functional groups (COF-NO2 and COF-NH2) were designed and prepared in order to enhance selective adsorption ability toward the Ketoprofen (KTP) molecule via functional group tuning. For KTP, due to amino group which could interact with not only carboxylic acid but also carbonyl group, COF-NH2 exhibited twice adsorption capacity as high as other two counterparts Ibuprofen (IBP) and Naproxen (NPX). However, there was no selectivity for those three NSAIDs when COFs containing nitro groups (COF-NO2) were used as adsorbents. We also found that the adsorption process followed the pseudo-second-order kinetic model well, which confirmed the capture of KTP onto COF-NH2 was dominated by chemical adsorption. The COF-NH2 will be a particularly promising porous adsorbent to selectively eliminate the KTP from effluents, and COFs with specific binding sites for various pollutants can be acquired via functional group tuning.