Understanding bisphenol-A adsorption in magnetic modified covalent organic frameworks: Experiments coupled with DFT calculations

Abstract A kind of magnetic covalent organic frameworks (Fe3O4@TpND) is successful synthesized by the solvothermal method. The synthesis process involves two steps, where the first step corresponding to the synthesis and amino- modification of magnetic particles (Fe3O4-NH2) and the second step launched with COF polymerization outside Fe3O4-NH2. This kind of novel materials (Fe3O4@TpND) could inherit the physicochemical superiority of COF plane and the easy recoverability of Fe3O4. The experimental results confirm that Fe3O4@TpND possessed a favorable adsorption capacity (114.97 mg L−1, at 298 K and pH 6.0), rapidly uptake rate, a broad pH range, and superior renewability on the removal of bisphenol-A (BPA). To shed more light on the sorption mechanism, both of static density functional theory (DFT) calculation and molecular dynamic (MD) simulation are introduced to portray the molecular-scale interaction between TpND and BPA. By exploring the geometric structures, as well as the energetic and electronic properties of the complex, the phenolic aldehyde groups in TpND were found to exert significant contribution to capture BPA molecules via the hydrogen bonding effects. From the perspective of dynamic MD simulation, the size of BPA cluster and physical pore structure of the adsorbent also possess a remarkable aggregating effect on the sorption process. Accordingly, this study provides crucial fundamental and valuable knowledge of COF materials applied in the field of water purification.