No abstract

Industrial wastewater organic pollutants such as phenol can be treated through adsorption on active surfaces. Herein, the adsorption mechanism and dynamic behaviors of phenol molecules onto covalent organic frameworks (COFs) with well-defined supramolecular structures are investigated via molecular dynamics and well-tempered metadynamics simulations under various external electric fields. The Lenard–Jones interaction is predominant during the adsorption process, while NH and OH groups in COFs and phenol, respectively, can increase the adsorption due to the electrostatic interaction. Besides, the adsorption affinity of phenol on COFs is weakened by increasing the electric field strength. In addition, the free energy values for the complexes with and without the external electric field at their global minima reached at about −264.68, −248.33, and −290.13 (for 1, 0.5, and 0 V nm−1) kJ mol−1, respectively. The obtained results confirmed the COFs as prominent adsorbents for loading phenol and its removal from the water-contaminated environment.

The Artificial water channels (AWCs) encapsulate water wires or clusters, analogous to natural porins, and offer iterative and continuous hydrogen bonding that plays an essential role in their stabilization. During the last few years, significant progress has been made in AWCs characterization and synthesis, and bridging these advancements to practical development remains a unique challenge. In this study, the possibility of high water selectivity and permeability, as well as the stability of the AWCs channel, is examined via classical molecular dynamic (MD) simulations and well-tempered metadynamics (Wt-metaD) simulations. The results of MD simulations demonstrated that AWCs could provide paths for rapid and selective water permeation via the formation of water-wire networks. Moreover, our findings revealed that the AWC is stable during the simulation time and non-bonded interactions, especially hydrogen bonding, have an essential role in forming a stable OH channel for transporting water molecules. However, the obtained water fluxes (L m−2 h−1) using nanofiltration AWC give us a high flux value, 19.08 (L m−2 h−1), 17.96, and 20.2 (L m−2 h−1), for AWC/ NO3−, AWC/Mg2+, and AWC/Ca2+, respectively. Well-tempered metadynamics simulations of water transport in the OH channel also report similar activation energy values and provide molecular-scale details of the mechanism for water entry into these channels. The free energy values for the AWC/water complexes at their global minima are about ~−241.912, ~−223.479, and ~−255.98 kJ mol−1 in systems AWC/NO3−, AWC/Mg2+, and AWC/Ca2+, respectively.