In recent years, scientific and industrial attention has shifted from the primary structure (chemical structure) of polysaccharides to their emerging functions derived from higher-order nanostructures when utilized as advanced materials. In particular, cellulose nanofibers (CNF) from trees and chitin nanofibers (CtNF) from crustaceans are fully extended, uniaxially oriented chain crystals that cannot be synthesized artificially [1]. These structural polysaccharides are characterized by a high aspect ratio, a uniform width of several nanometers, and a fiber length ranging from several hundred nanometers to several micrometers. They also exhibit structural regularity at the interface and high crystallinity inside. Due to their large specific surface areas, various studies are being conducted on their catalytic applications, such as catalyst supports for nanometals and enzymes. In addition, organocatalysts are being investigated that use polysaccharide functionalities as acid/base and chiral catalysts [2] (Fig. 143.1). Research and development of CNF as a composite nanomaterial is promising due to its specific strength, which is five times stronger than that of steel at one-fifth the density. Applications include automotive parts requiring light weight and high strength, such as the Ministry of Environment’s Nano Cellulose Vehicle (NCV), resin composites for housing and building materials, and electronic devices, sensors, and optical materials [1, 3].