Cellulose Nanofibers: Current Status and Emerging Development of Sources, Pretreatment, Production, and Applications

With the increase in global demand for sustainable alternatives to fossil fuel consumption, the development of green technologies and novel materials in various industries is becoming crucial. Cellulose nanofibers (CNFs), derived from abundant and renewable sources such as wood and agricultural residues, have received enormous interest in various industries due to their exceptional mechanical, thermal, and rheological properties, tunable surface chemistry, and enhanced economic and environmental benefits. Due to the variation in production technologies and process parameters, CNFs exhibit characteristic crystallinity and surface chemistry, leading to different quality and performance of the final product. This review delves into the diverse aspects of CNFs, including their sources, pretreatment approaches, and production techniques, aiming to provide a better understanding of the production-structure-functionality-application correlations, thus making it possible to more efficiently utilize biomass and their CNFs. Then, the recent emerging applications of CNFs are summarized to explore more possibilities for the next generation of advanced materials. Finally, the challenges and opportunities, as well as future perspectives, of CNFs are outlined.