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1.D.304.  The Crown Ether Crystal Na+ Pore (CECNaP) Family 

Emulating biological sodium ion channels to achieve high selectivity and rapid Na+ transport is important for water desalination, energy conversion, and separation processes. However, the development of artificial ion channels, especially multichannels, to achieve high ion selectivity, remains a challenge. Feng et al. 2024 demonstrated the fabrication of ion channel membranes utilizing crown-ether crystals (DA18C6-nitrate crystals), which feature extremely consistent subnanometer pores. The polyethylene terephthalate (PET) membranes were initially subjected to amination, followed by the in situ growth of DA18C6-nitrate crystals to establish ordered multichannels aimed at facilitating selective Na+ conductance. These channels allowed rapid Na+ transport while inhibiting the migration of other ions (K+ and Ca2+). The Na+ transport rate was 2.15 mol m-2 h-1, resulting in the Na+/K+ and Na+/Ca2+ selectivity ratios of 6.53 and 12.56, respectively. Due to the immobilization of the crown-ether ring, when the size of the transmembrane ion exceeded that of the crown-ether ring's cavity, the ions had to undergo a dehydration process to pass through the channel. This resulted in the ions encountering a higher energy barrier upon entering the channel, making it more difficult for them to permeate. However, the size of Na+ was compatible with the cavity of the crown-ether ring and was able to displace the hydrated layer effectively, facilitating selective Na+ translocation. Thus, this research offers a promising approach for the future development of functionalized ion channels and efficient membrane materials tailored for high-performance Na+ separation (Feng et al. 2024).

References associated with 1.D.304 family:

Feng, Y., S. Xu, J. Zheng, L. Huang, T. Ye, G. Wang, Y. Jiang, and N. Liu. (2024). Crown-Ether Crystal Channel Membranes with Subnanometer Pores for Selective Na Transport. ACS Appl Mater Interfaces 16: 26817-26823. 38727564