Nanocomposite films of cellulose nanofiber/azodianiline covalent organic framework as electrode materials

Abstract The present research focused onto nanocomposite films composed of covalent organic frameworks (COFs) and cellulose nanofiber (CNF) for potential usage in energy storage devices. To this end, two azodianiline‐based COFs were dispersed by 1.0 wt% in CNF and cast into films. Results showed that the overall roughness increased upon incorporation of COFs into CNF. In addition, hydrophilicity and surface energy of nanocomposite films were found lower than those of pure CNF, while elongation at break of nanocomposite films was enhanced compared to pure CNF. The crystalline structure of COFs was preserved after composite formation. Pore size analysis demonstrated that specific surface area of nanocomposite films was around 900 m 2 /g in comparison with 93 m 2 /g for pure CNF. In addition, pore size distribution was found narrower for nanocomposite samples. Nanocomposite films were found more thermally stable than pure CNF; mass loss rate was slower and final residual mass was higher. Electrochemical analyses revealed outstanding improvements on COF addition, where specific capacity of 590 C/g, specific capacitance of 119 F/g, energy density of 26.3 Wh/kg, and power density of 390 W/kg were obtained. The findings indicated that CNF/COF nanocomposite films could be used as potential electrode materials for energy storage purposes. Highlights Composites of cellulose nanofiber and covalent organic framework are studied. Specific surface area is improved upon COF addition into CNF matrix. Thermal properties and elongation at break are enhanced on COF incorporation. Specific capacity, power density, and energy density are markedly increased. CNF/COF composites are found to be of potential use in electrode materials.