Macrocycle-based covalent organic networks for ultrafast sub-1-Å precision ion sieving

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• The water-energy nexus requires advanced membranes for precise ion separation.
• Conventional materials face limitations in achieving subångström ion-sieving precision.

Purpose of the Study:

• To develop ultrathin covalent organic network (CON) membranes with subångström ion-sieving capabilities.
• To engineer membranes for efficient ion separation in water-energy systems and industrial wastewater treatment.

Main Methods:

• Fabrication of CON membranes via interfacial polymerization of cyclen with terephthaloyl or isophthaloyl chloride.
• Tuning monomer conformation to engineer pore size and ion selectivity.
• Process scale testing for lithium extraction and chloride production.

Main Results:

• CON membranes exhibited narrow pore size distribution and subångström ion resolution.
• CON-T membranes showed high water permeance (22.2 L/m²/h/bar) and selectivities (Li+/Mg2+: 82.6, Cl-/SO42-: 118.1).
• CON-I membranes achieved superior selectivities (Li+/Mg2+: 326.7, Cl-/SO42-: 376.9).
• Successful application in lithium resource extraction (97.4% recovery, 99.3% purity) and chloride production from wastewater (~99.9% purity).

Conclusions:

• The developed CON membranes offer a paradigm for high-resolution ion-sieving.
• This methodology is compatible with industrial-scale membrane manufacturing.
• These membranes provide a viable solution for next-generation water-energy systems and resource recovery.