(29g) MOF-Functionalized Hybrid Cellulose Nanofibrous Aerogels

There is a rising interest in sustainable approaches that develop multifunctional materials without heavy use of organic solvent and multiple reaction steps. Amongst recently developed multifunctional materials metal-organic frameworks (MOFs) - porous crystalline substances belonging to a group of coordination polymers rank high. Their three-dimensional network structure with exceptionally high surface area and pore volume makes them highly desirable for multitude of applications such as gas storage, separation, catalysis, sensing, drug delivery, and energy storage. However, MOFs are typically produced as powder, which underscores the need to broaden their applications by integrating them into a robust host matrix. Aerogels, characterized by their ultra-lightweight nature, exceptional porosity, low density, and high specific surface area, emerge as optimal candidates for this purpose (Pirzada et al., Adv. Func. Mat. 2020). In this study, we explore multiple innovative approaches for synthesizing MOFs on 3D-structured hierarchically porous nanofibrous aerogels (NFAs) using cellulose-based hybrid NFAs as a sustainable and scalable material platform. The highlighting feature of these MOF-hybrid aerogels lies in the solvent-free fabrication without the use of harsh solvents unlike conventional MOF-hybrid aerogels that use a solvothermal approach. We compare MOFs grown using different pathways of introducing the metal-oxide precursor notably through atomic layer deposition (ALD), in-situ introduction in the nanofibers through electrospinning and by the growth of metal-oxide nanorods on the NFAs. The resulting 3D structure exhibits elasticity, low density (~10 mg/cm³), and hierarchical porosity comprising primary (1-5 µm) and secondary pores (10-60 µm). Mechanical compressibility tests confirm the durability and resilience of the MOF-NFAs, making them suitable for mechanically stressful environments. The developed aerogels (Rahmanian et al., J. Mat. Chem. A, 2024) demonstrate high CO₂ adsorption capacity (4.04 mmol/g), demonstrating outstanding performance in CO₂ separation and selectivity. Incorporating MOFs into the aerogel structure maximizes surface area and exposes active sites within the micropores of ZIF-8, facilitating efficient CO₂ molecule adsorption. Additionally, the aerogel exhibits remarkable efficacy in removing heavy metals, specifically Cu(II) ions (>99% removal), attributed to the thin and uniform ZIF-8 coating on the NFA exposing their active sites for enhanced interaction with target pollutant. These hybrid NFAs hold promise across various fields, including environmental and biomedical applications, encompassing sorption, catalysis, filtration, and water purification.