Quinone–Phenol Redox-Enhanced CO ₂ Incorporation Enables Cross-Linking between Microcrystalline Cellulose and Chitosan, Producing Hyper-Branched Adhesives

Graft copolymerization remains challenging for natural biomass polysaccharides due to their inertness of rigid, orientated, and complex structures. In this study, CO2 incorporation enables cross-linking between microcrystalline cellulose (MTC) chains, and the CO2 grafting efficiency was significantly enhanced via the quinone–phenol redox effect, enabling the synthesis of hyperbranched cellulose–chitosan polymers. The resulting cellulose–CO2–chitosan resin exhibited excellent adhesive mechanical performance, achieving a tensile shear strength of 1.42 MPa even after a 3 h hot-water immersion test. A scalable manufacturing process was successfully developed, enabling the production of up to 50 kg of adhesive suitable for industrial plywood applications. This method eliminates the conventional stoichiometric consumption of oxidates such as TEMPO, periodates, and other catalysts in cellulose functionalization. It presents a promising and sustainable strategy for employing CO2 as an efficient, environmentally benign cross-linker in natural polysaccharide-based polymer structures, demonstrating both high synthetic efficiency and practical scalability.