Bifluorinated Motif‐Tailored Hybrid Membranes for Ultra‐Permeable CO 2 Separation From Air Under High Humidity
Jinjin Liu, Bingjie Wang, Zhibin Wang, Yuxiu Sun, Zhengqing Zhang, Yi Yang, Zhihua Qiao, Benqiao HeABSTRACT
Membrane‐based direct air capture (m‐DAC) offers an energy‐ efficient route to mitigate rising atmospheric CO 2 , but its practical deployment is hindered by low CO 2 concentration and high humidity. Herein, we propose a “Sailing‐with‐Water” strategy that turns humidity from an obstacle into a mass‐transfer driving force. The bifluorinated motifs are engineered by integrating fluorinated ionic liquid@UiO66 (IL@UiO) as porous fillers and a novel polymer, PIM‐1DFBP, as the second fluorine source. The abundant fluorine sites within the membrane facilitate CO 2 capture and enrichment from dilute streams via Lewis acid–base interactions. Notably, under high humidity conditions, the fluorine sites in the membrane form a hydrogen‐bond network with water molecules, creating a polar microenvironment that further enhances CO 2 affinity and builds ultrafast channels for CO 2 permeation. The optimized membrane achieves a CO 2 permeability of 12697.08 Barrer and CO 2 /N 2 selectivity of 44.06 under 65% relative humidity, surpassing the 2019 Robeson upper bound. The membrane also exhibits 180‐days stability, large‐area defect‐free fabrication, and process simulation shows that only 612.37 m 2 is needed to reach 40% CO 2 outlet concentration. This work provides a humidity‐resistant paradigm for high‐performance m‐DAC.