Hydrophobic Polymer-Coated and Uncoated ZIF-67/Alumina Membrane for Volatile Organic Compound Degradation and CO₂...

A major obstacle to the commercial application of metal-organic frameworks (MOFs) is that their powder form hinders scalable membrane fabrication and significantly compromises stability under humid conditions. To address these limitations, this study presents a novel, humidity-resistant zeolitic imidazolate framework ZIF-67/alumina composite membrane (MMF) that combines visible-light volatile organic compound (VOC) degradation and CO₂ adsorption in a single, scalable platform. Using an in situ self-conversion strategy, ZIF-67 crystals were directly anchored onto porous alumina, providing strong interfacial bonding, mechanical durability, and efficient mass transport. The MMF exhibited excellent toluene adsorption, as described by the Langmuir model, and achieved 96.4% photocatalytic degradation under visible light. Radical-trapping and Electron spin resonance (ESR) studies confirmed superoxide anions (^.O₂ ^-) as the dominant active species. The photocatalytic performance declined at 70-80% relative humidity (RH). To overcome this, ultrathin hydrophobic polysiloxane and perfluorinated polymer coatings minimized water uptake and maintained >92% photocatalytic activity, as supported by water vapor isotherms. Beyond VOC abatement, the MMFs demonstrated promising CO₂ adsorption predominantly by physisorption with higher uptake at low temperature and high pressure, attributed to enhanced pore filling and van der Waals interactions with nitrogen-rich active sites. This work establishes a scalable strategy for MOF-based membranes for simultaneous VOC abatement and CO₂ capture, offering a promising pathway for air-purification technologies.