Bifluorinated Motif‐Tailored Hybrid Membranes for Ultra‐Permeable CO ₂ Separation From Air Under High Humidity

Abstract

ABSTRACT 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.