Density functional theory study of emerging pollutants removal from water by covalent triazine based framework

In this work porous covalent triazine based frame-work (CTF) is investigated for the removal of emerging pollutants methyl- and propylparaben (MeTP and ProP) using density functional theory approach. Various adsorption configurations of these pollutants over the CTF are evaluated by computing geometrical parameters, adsorption energies (E-ad), thermodynamic parameters, total density of states (TDOS), atom in molecule (AIM), natural bonding orbital (NBO), reduced density gradient (RDG) and noncovalent interaction (NCI) analysis. The E-ad ranges from -5.92 kcal/mol to -11.70 in gas phase and - 2.50 kcal/mol to -9.57 kcal/mol in solvent phase for MeTP@CTF while -7.04 kcal/mol to -10.23 kcal/mol and - 534 kcal/mol to -7.37 kcal/mol is noticed for ProP@CTF, respectively. The negative values of E-ad, Delta H (-3.90 to -9.30 kcal/mol) and Delta G (-2.96 to -8.91 kcal/mol) for all the adsorption configurations confirm the energetic favorable, exothermic and hence spontaneous/feasible nature of the process. The reduction in the energy gap (E-gap) shown by TDOS results described the sensitivity of CTF towards the MeTP and ProP. The higher sensitivity of CTF towards both molecules is shown in adsorption configuration 2. The results of AIM, NBO, RDG and NCI analysis are in agreement with the TDOS analysis and confirm that the adsorption occurred through intermolecular hydrogen bonds. These results suggest that CTF can be used as a potent adsorbent for the purification of water from these emerging pollutants. (C) 2020 Elsevier B.V. All rights reserved.