CO₂ Hydrate Formation Kinetics Using Aqueous MOF Ink-Soaked Water Absorbing Materials

Although numerous studies have focused on gas hydratesusing water-adsorbentmaterials, there is a lack of a detailed understanding regarding therole of water-absorbing materials in hydrate formation. This studytested everyday-purpose water-absorbing hygroscopic materials suchas textile fabrics, bamboo wipe fibers, and baby diaper foam for theirrole in CO2 hydrate formation. These materials are highlyhydrophilic, readily available commercially, and affordable and exhibithigh water retention capabilities. The kinetics of CO₂ hydrateformation using these water-soaked hygroscopic materials are investigatedusing a rocking cell reactor under constant ramping and isothermaltemperature programs. The study evaluated the influence of materialwetness, the presence and concentration of metal–organic frameworks(MOFs) (HKUST-1, MIL-53(Al), and MOF-303) in water, and the temperatureon the nucleation temperature, induction time, water-to-hydrate conversion,and total mmol of CO₂ per gram of material. Results indicatedthat above temperatures exceeding 1 °C, chenille fabrics, bamboowipes, and polyether polyurethane foam (PPU) did not exhibit significantnucleation temperatures or trends. Conversely, at temperatures below0 °C, only PPU-based CO₂ hydrate studies demonstratedrapid pressure drops, confirming high water-to-hydrate conversion.PPU materials soaked in water-based MOF ink showed induction timeslower than those in water or SDS solution. Among the water-based MOFinks, MOF-303 ink exhibited the best stability, CO₂ inductiontimes, and total CO₂ captured in hydrates. PPU materialperformance was due to embedded superabsorbing polymers (SAP) intononwoven fabrics, which improved the contact area between liquid andgas compared to those studies where SAP was used in powdered form.Furthermore, PPU materials demonstrated high water retention, evenafter multiple cycles of formation and dissociation. Comparative benchmarksagainst other wet solid porous materials showed that PPU achieveda maximum CO₂ uptake in hydrates of approximately 32 mmolper gram of material at an initial starting pressure of 30 bar andwhen temperature reached