Many regions of the world suffer from a scarcity of drinking water but are close to an ocean. The desalination of seawater is, thus, an important technology. Membrane desalination methods constitute a common solution for obtaining fresh water from seawater. In addition to osmosis-driven filtration membrane processes (i.e., reverse osmosis and forward osmosis), membrane distillation is an interesting approach. In membrane distillation, water vapor is driven through a porous hydrophobic membrane by a thermal gradient. It could serve as a sustainable process when renewable energy is used.

Zhigao Zhu, Shanghai Advanced Research Institute, Chinese Academy of Sciences, and Nanjing University of Science and Technology, China, Xing Liu, Shanghai University, China, Gaofeng Zeng, Shanghai Advanced Research Institute and University of the Chinese Academy of Sciences, Beijing, and colleagues have developed a membrane for ultrafast desalination based on a conjugated alkadiyne–pyrene framework (pictured schematically), supported on porous copper hollow fibers. The support material was activated with pyridine. The team then used 1,3,6,8-tetraethynylpyrene as a precursor for the conjugated framework poly(1,3,6,8-tetraethynylpyrene) (PTEP), which was formed on the support via a catalytic cross-coupling reaction.

The resulting composite membrane showed high water permeability and nearly complete ion rejection when used in membrane distillation. The water flux was found to be an order of magnitude higher than that of a commercial poly(vinylidene fluoride) (PVDF) membrane. According to the researchers, other alkadiyne-containing membranes could possibly be developed under similar conditions and used for efficient separation processes.

• Alkadiyne–Pyrene Conjugated Frameworks with Surface Exclusion Effect for Ultrafast Seawater Desalination,
  Dian Gong, Binghai Wen, Lu Wang, Hongxuan Zhang, Huiling Chen, Jingrui Fan, Zhi Li, Long Guo, Guosheng Shi, Zhigao Zhu, Xing Liu, Gaofeng Zeng,
  J. Am. Chem. Soc. 2024.
  https://doi.org/10.1021/jacs.3c10051