Nanocellulose and Metal-Organic Framework-Based Composites : Synthesis, Characterization, and Applications

Abstract: Nanocellulose is one of the most promising of the green materials available for use in a sustainable economy because of its natural abundance and renewability. Compared to petroleum‒derived synthetic polymers, nanocellulose has many unparalleled advantages such as its unique nanofibrous structure, high thermal stability, mechanical flexibility, rich surface chemistry, biocompatibility, and biodegradability. The tremendous potential of nanocellulose has recently been realised in its use as a building block substrate for multifunctional applications such as energy storage devices, flexible electronic devices, and advanced filtration units. In future, more insight will be gained into the fundamental structure−function relationships of nanocellulose‒based functional materials, with subsequent advantages for the materials industry.Metal–organic frameworks (MOFs) are an emerging family of coordination polymers with unique crystalline porous features. Because of their diverse design principles and facile chemical synthesis processes, thousands of MOFs are currently under development. MOFs have found huge application value in many fields, including gas separation and storage, energy storage, industrial catalysis, and so on. However, control of the microscopic dimensions and crystal alignments of MOFs remains a big challenge. The insolubility and brittleness of MOF crystals have also resulted in problems with shaping and processing these substances. These problems have restricted the broader application of MOFs. This thesis explores the concept of nano‒composition with a focus on a previously little explored pathway for processing MOFs with the assistance of Cladophora cellulose (CC) extracted from green algae. Firstly, interfacial synthesis was developed through collaborative coordination of metal ions between the carboxyls on CC and the ligands in MOFs (Paper I). This approach enabled the continuous growth of MOF crystals along the CC to form core–shell hybrid CC@MOF nanofibers. These nanofibers were processable in aqueous solution, enabling facile fabrication of various bulk materials such as films (Paper I) and aerogels (Paper II). The CC@MOF composites had hierarchical porosity, good mechanical flexibility, low thermal conductivity, and high thermal stability. Various applications of the CC@MOF composites have subsequently been demonstrated; these include thermal insulation and fire retardancy (Paper II), electrochemical energy storage (Paper III), photothermal conversion evaporation for efficient water desalination (Paper IV), and solar‒driven ionic power generation (Paper V). This thesis covers the synthesis, structural characterization, and proof‒of‒concept applications of the CC@MOF composites, providing a basic understanding of the relationships between the structure and performance of composite materials.