Multivariate Covalent Organic Frameworks for High-Performance Ammonia Nitrogen Separation:
Yunhui Zhang1,2,3,4, Jinglin Liu1, Tao Wang1
1College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China.
Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
|April 1, 2025
Summary
Researchers developed sulfonated covalent organic frameworks (COFs) for efficient ammonia nitrogen (NH4+-N) removal from water. These novel materials exhibit high adsorption capacity and ultrafast kinetics, offering a promising solution for water decontamination.
Area of Science:
- Materials Science
- Environmental Chemistry
- Nanotechnology
Background:
- Ammonia nitrogen (NH4+-N) removal from water is crucial for environmental protection and resource recovery.
- Adsorbing NH4+-N is challenging due to its stable structure and large ionic radius compared to other cations.
- Covalent organic frameworks (COFs) offer tunable structures for adsorption applications.
Purpose of the Study:
- To design and synthesize sulfonated COFs for enhanced NH4+-N adsorption.
- To investigate the structure-property-function relationships governing NH4+-N adsorption in COFs.
- To elucidate the atomic-level mechanisms of NH4+-N adsorption.
Main Methods:
- A "multivariate" synthetic strategy was employed to create sulfonated COFs.
- The adsorption performance of COFs with varying sulfonic acid group densities was evaluated.
- N K-edge near-edge X-ray absorption fine structure spectroscopy was used to study adsorption mechanisms.
Main Results:
- The optimal sulfonic acid group density of 50% yielded an adsorption capacity of 17.09 mg g-1 and an equilibrium time of 5 min.
- COF crystallinity positively impacted adsorption capacity and kinetics.
- Surface area and hydrophilicity enhanced capacity, while pore size affected capacity and kinetics differently.
- Ion exchange and hydrogen bonding were identified as key adsorption mechanisms.
Conclusions:
- Sulfonated COFs demonstrate superior performance for NH4+-N capture compared to existing adsorbents.
- Material properties like crystallinity, surface area, hydrophilicity, and pore size critically influence adsorption.
- This study provides a framework for designing advanced adsorbents for efficient cation removal.
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