Metal Organic Framework Impregnated Nanofibrous Aerogels: A 3D Structured Matrix for CO₂ Capture

This study explores the synthesis and functionality of mesoporous UiO-66-NH₂ metal-organic framework (MOF) impregnated cellulose diacetate (CDA)-silica hybrid nanofibrous aerogels (NFAs) for selective CO₂ capture. Mesoporous MOFs generally outperform microporous MOFs for CO₂ capture, while NFAs provide a lightweight, highly porous material platform consisting of a three-dimensional (3D) network of interlinked nanofibers, offering both mechanical strength and a larger surface area. We exploit the attributes of these candidate materials by producing CDA-silica@UiO-66-NH₂ NFA through a simple freeze-drying process involving a mixture of CDA-silica nanofiber dispersions and mesoporous UiO-66-NH₂ nanoparticles in tert-butanol, avoiding cumbersome pre- or postprocessing typical in aerogel synthesis. The aerogels exhibit a hierarchical porous structure, allow for MOF loadings of up to 80 wt %, and demonstrate remarkable CO₂ adsorption performance, with a direct correlation between MOF content and adsorption efficiency. Notably, an NFA containing 80 wt % MOF achieves a CO₂ uptake of 2.5 mmol/g at 35 °C and atmospheric pressure. The CDA-silica@UiO-66-NH₂ NFA also exhibits a strong preference for CO₂ adsorption compared to N₂ across all pressure levels when exposed to a gas mixture of CO₂ and N₂ in an 85:15 ratio. The CO₂/N₂ selectivity (<i>S</i>_ads) usually calculated by using the ideal adsorption solution theory (IAST) reveals a value of 18.2 at 298 °K for this system. The NFA also displays strong mechanical resiliency including compressibility and fatigue resistance, and MOF integration without detachment during multiple compression cycles. Unlike traditional CO₂ capture materials, our CDA-silica@UiO-66-NH₂ NFA with a combination of high CO₂ selectivity, structural integrity, and ease of fabrication thus offers a potentially scalable solution that addresses both performance and durability in real-world applications.