Bifluorinated Motif-Tailored Hybrid Membranes for Ultra-Permeable CO₂ Separation From Air Under High Humidity

Membrane-based direct air capture (m-DAC) offers an energy- efficient route to mitigate rising atmospheric CO₂, but its practical deployment is hindered by low CO₂ 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 CO₂ 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 CO₂ affinity and builds ultrafast channels for CO₂ permeation. The optimized membrane achieves a CO₂ permeability of 12697.08 Barrer and CO₂/N₂ 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 m² is needed to reach 40% CO₂ outlet concentration. This work provides a humidity-resistant paradigm for high-performance m-DAC.