Original Title: Chinese Scholars Make Progress in Covalent Organic Framework Membrane Distillation for Seawater Desalination Author: Yue Qin Kangqiang Published by: Department of Chemical Sciences Professor Wang Bo and Professor Feng Xiao's team of Beijing Institute of Technology and Professor Wang Fengchao's team of University of Science and Technology of China cooperated to make progress in the field of membrane distillation seawater desalination under the support of NSFC programs (Approval No.: 21625102, 21971017, 21922502, 21674012). The research results are entitled "Membrane Distillation of Covalent Organic Framework Thin Films with Hydrophobic Gradient (Hydrophilicity gradient in covalent organic frameworks for membrane distillation)". Published online July 22, 2021 in the journal Nature Materials. Thesis connection: https://doi.org/10.1038/s41563-021-01052-w. Figure. (A) Schematic of competitive reversible covalent bonding strategy. (B) Comparison of water transport channels in hydrophilic, hydrophobic, COF, and defect-engineered COF membranes during membrane distillation. With the rapid growth of global population and the continuous development of industry, thin film distillation ,50l rotovap, the shortage of freshwater resources has become a global problem to be solved urgently. Seawater desalination is an effective way to solve the problem of freshwater crisis. Among various desalination technology, membrane distillation (MD) utilizes that vapor pressure difference across a membrane as a driving force for mas transfer and thermally driven desalination of water vapor across a porous hydrophobic membrane material, It has great advantages in the treatment of high-concentration and high-pollution saline and the utilization of low-grade heat such as industrial waste heat, solar energy and geothermal energy. However, the further development of membrane distillation technology is limited by the problems of low flux, membrane fouling and membrane wetting of traditional polymer hydrophobic MD membranes. To solve the above problems, based on the two-dimensional covalent organic framework (COF) film with regular nanopores, the research team prepared COF films with pore size and hydrophilic and hydrophobic environment changing with depth gradient by introducing competitive reversible covalent bonding strategy (see figure). And that high-flux membrane distillation seawater desalination is realize. On the one hand, the ultrathin hydrophobic separation layer (short mass transfer path) and the vertically penetrating nanopores (low curvature) greatly reduce the transmembrane resistance of water vapor; on the other hand, the confined nanopores have an enhanced effect on water evaporation. The COF composite membrane had a NaCl rejection of 99.99% and a flux of 220 L m – 2 H – 1 (3.5 wt.% NaCl solution as feed solution, test temperature 65 oC). In addition,wiped film distillation, the pore size and hydrophilic-hydrophobic gradient constructed in the COF film endow the membrane material with anti-fouling performance. The enhancement of the electrostatic repulsion in the nano-pore delays the crystallization of the salt on the pore wall, reduces the membrane infiltration risk, and ensures that the separation membrane has long-term operation stability. Return to Sohu to see more Responsible Editor:. toptiontech.com