Metal-Organic Frameworks Coated Cellulose Nanofibers for Localized Carbon Dioxide Capture

The consequences of global warming due to increasing levels of greenhouse gas emissions stress the need to develop carbon capture technologies expeditiously. Metal-organic frameworks (MOFs) have been proven to be effective carbon dioxide (CO₂) sorbents, but challenges lie in their integration into practical applications owing to the hurdles in processing the powder MOFs into usable structures. Herein, the Cu-MOFs nanocrystals were in situ grown over different cellulose substrates, including bacterial cellulose nanofibers lamellas (BCNFLs) and wood-derived cellulose nanofibers (WCNFs). The successfully prepared sorbents were evaluated for CO₂ capture applications, along with their kinetic and diffusion dynamics. The loading of MOFs nanoparticles was confirmed via FESEM, showing the interconnected network of cellulose nanofibers (CNFs) and interwoven MOFs particles. The surface area and porosity of the samples, analyzed by the N₂ sorption method, were proportional to the MOFs in the sorbents. The MOFs/BCNFLs and MOFs/WCNFs composites demonstrated CO₂ uptake of approximately 1 and 1.19 mmol/g, respectively, and maintained stability over numerous cycles, highlighting the robustness of the developed structures. The CO₂ sorption isotherms were explained by the Langmuir–Freundlich model, accounting for surface heterogeneity, and exhibited a selectivity ($$) of 49 with a heat of adsorption of 27 kJ/mol. The MOFs/BCNFLs exhibited 2.2 times higher sorption kinetics and a 25% greater diffusion coefficient than WCNFs, attributed to the thin MOFs layer that minimized mass transport limitations. Our findings underscore the significance of structural optimization and the potential of cellulose nanofiber-coated MOFs for practical carbon capture applications.