Architectural design of 2D covalent organic frameworks (COFs) for pharmaceutical pollutant removal

Macrolide antibiotics, including erythromycin, clarithromycin, and azithromycin, are frequently misused for human treatment globally. Therefore, they were considered high-risk substances on the Union-wide monitoring Watch list under Regulation 2018/840/EU. The present work investigates the adsorption behavior of the pharmaceutical pollutants on the 1,3,5-tris (4-aminophenyl) benzene/2,5 dimethoxyterephthalaldehyde (TAPB-DMTP) covalent organic frameworks (COFs). In this study, we employ molecular dynamics simulations and well-tempered metadynamics to evaluate the adsorption affinity of pristine covalent organic frameworks and their functionalized form (F-COFs) for the removal of four distinct pharmaceutical pollutant molecules (PPMs): erythromycin (EMC), dexamethasone (DEG), azithromycin (AZM), and clarithromycin (CMC). We utilized MD simulations to examine the impact of two different temperatures (298 and 310 K) on enhancing the adsorption of the pharmaceutical contaminants from wastewater by COFs/F-COFs. To evaluate this process, several descriptors are calculated from the simulation trajectories, including interaction energies, root-mean-square deviation, radial distribution function, solvent-accessible surface area, mean square displacement, and the number of hydrogen bonds (HB). It is determined that HB and X-HMIDLINE HORIZONTAL ELLIPSIS pi (X = C, N, O; pi = aromatic system) interactions are the most critical factors contributing to system stability. In addition, it is shown that COFs with a pore-based structure have a higher capacity for removing pollutants. The free energy landscapes confirm that the global minimum is typically associated with the formation of hydrogen bonds. At 298 K, their global minima are DEG/F-COFs = -665.81, AZM/F-COFs = -638.53, EMC/F-COFs = -566.31, and CMC/F-COFs = -326.75 KJ mol-1.