Temperature-induced formation of cellulose nanofiber film with remarkably high gas separation performance

Free-standing cellulose nanofiber (CNF) films were prepared by a specially designed oven-drying approach. For the first time, the evaporation rate was carefully controlled to enhance the gas separation performance of the CNF film with the highest H-2/N-2 and H-2/O-2 selectivities of 159.4 and 218.2, respectively. The dense structure formed by the CNFs and the intra- and inter-fibrillar hydrogen bonds are believed to contribute to the separation property. Particularly, the specific role of floating-shape film precursor formed at the rapid evaporation stage (stage I) and the mechanism for film formation were investigated. This study demonstrated that the evaporation rate controlled by the heating temperature exhibited significant influence on surface, uniformity and gas separation of the CNF films.