Leaf-like ionic covalent organic framework for the highly efficient and selective removal of non-steroidal anti-inflammatory drugs: Adsorption performance and mechanism insights

In recent years, ionic covalent organic frameworks (iCOFs) have become popular for the removal of contaminants from water. Herein, we employed 2-hydroxybenzene-1,3,5-tricarbaldehyde (TFP) and 1,3-diaminoguanidine monohydrochloride (DgCl) to develop a novel leaf-like iCOF (TFP-DgCl) for the highly efficient and selective removal of non-steroidal anti-inflammatory drugs (NSAIDs). The uniformly distributed adsorption sites, suitable pore sizes, and functional groups (hydroxyl groups, guanidinium groups, and aromatic groups) of the TFP-DgCl endowed it with powerful and selective adsorption capacities for NSAIDs. Remarkably, the optimal leaf-like TFP-DgCl demonstrated an excellent maximum adsorption capacity (1100.08 mg/g) for diclofenac sodium (DCF), to the best of our knowledge, the largest adsorption capacity ever achieved for DCF. Further testing under varying environmental conditions such as pH, different types of anions, and multi-component systems confirmed the practical suitability of the TFP-DgCl. Moreover, the prepared TFP-DgCl exhibited exceptional reusability and stability through six adsorption–desorption cycles. Finally, the adsorption mechanisms of NSAIDs on leaf-like TFP-DgCl were confirmed as electrostatic interactions, hydrogen bonding, and π-π interactions. This work significantly supplements to our understanding of iCOFs and provides new insights into the removal of NSAIDs from wastewater.