Ionic Hydrophobic Gates on Metal–Organic Frameworks Enable High-Purity CO2 Separation from Humid Flue Gas
Deyun Sun; Shangqing Chen; Miao He; Hongxue Xu; Yongxiang Sun; Lijuan Shi; Hongbo Zeng; Qun Yi
Journal of the American Chemical Society https://doi.org/10.1021/jacs.5c02093
ABSTRACT: Efficient extraction of high-purity CO2 from humid flue gas via adsorptive separation offers a promising and sustainable solution for carbon reduction and downstream applications. However, the coadsorption of H2O vapor and N2 from humid flue gas remains a persistent challenge that limits separation efficiency. To overcome this issue, this work introduces a novel concept of ionic hydrophobic gates on porous adsorbents, which enables one-step separation of high-purity CO2 directly from humid flue gas. By assembling hydrophobic ionic liquids and fluorine-rich terephthalaldehyde onto the surface of a metal−organic framework (MOF), this design establishes H2O barriers and CO2 channels on the outer shell while maintaining pore integrity in the core. The resulting core−shell material demonstrates exceptional CO2 adsorption capacity and an extraordinary CO2/N2 selectivity of 1780 (15/85, v/v), surpassing conventional adsorbents. Notably, dry CO2 with 99.999% purity is successfully extracted from humid flue gas (relative humidity, RH = 100%) in a single breakthrough experiment. In situ diffuse reflectance Fourier transform infrared spectroscopy (in situ DRIFTS) and density functional theory calculations reveal that fluorine-rich hydrophobic sites act as effective H2O barriers, while ionic liquid segments facilitate the transport of CO2 through hydrogen bonding and electrostatic interactions. Owing to its excellent scalability and broad compatibility with diverse MOF platforms, this ionic hydrophobic gating strategy offers a robust and versatile approach for constructing advanced gas separation materials, holding great promise for industrial applications in carbon capture, clean energy, and sustainable chemical processes.
图1. 离子疏水门控设计示意图
该研究通过在金属有机框架材料（MOFs）表面组装疏水性离子液体和富氟对苯二甲醛，构建了兼具H2O渗透屏障和CO2选择性传输通道的双功能壳层，同时保持MOFs内核的晶体结构和孔道完整性。在模拟工业烟道气的吸附分离测试中，该材料表现出卓越性能：CO2/N2选择性高达1780（15/85，v/v），可从高湿烟气（RH=80%）中直接获取纯度99.999%的CO2。该设计巧妙解决了吸附材料“疏水性”与“CO2选择性”难以兼得的行业痛点，实现了从高湿度烟道气中一步分离超高纯度CO2的突破性进展。此外，该策略展现出良好的通用性与循环稳定性，为潮湿工况下的低能耗、高效率碳捕集提供了新思路。
图2. MOF@IHG潮湿烟气分离CO2性能图
图3. 原位DRIFTS谱和吸附能计算
图4. 离子疏水门控潮湿烟气选择性分离CO2机理
