Frontiers in cellulose@COFs composites: From multiform fabrication toward emerging applications in separation, environment, and energy

As two distinct classes of functional materials, covalent organic frameworks (COFs) and cellulose have respectively emerged as typical synthetic porous crystals and renewable nanoscale building blocks for next-generation applications. Recent advances highlight that their synergistic integration creates composite architectures with emergent properties surpassing individual component capabilities, particularly in crystallinity modulation, pore size engineering, and mechanical reinforcement. Through strategic coupling via covalent conjugation, electrostatic assembly, or supramolecular interactions, these composite systems can be engineered into hierarchical architectures, including freestanding membranes, ultralight aerogels, and stimuli-responsive hydrogels. Such structured composites demonstrate unprecedented performance metrics in critical technological domains spanning molecular separation (nanofiltration/gas purification), sustainable water remediation, solar-driven energy conversion, and environmental energy harvesting. This review systematically examines state-of-the-art fabrication strategies for COF-cellulose composites, with particular emphasis on structure-property correlations. We critically assess their various applications while addressing persistent challenges in scalable manufacturing, interfacial compatibility, and long-term stability. This work establishes a framework for advancing these cpmposite materials toward practical implementation by delineating fundamental design principles and technological bottlenecks. The progressive understanding of their multiscale interactions, coupled with emerging sustainable processing techniques, positions COF-cellulose composites as a transformative materials platform for addressing global sustainability challenges.