Cellulose Nanomaterials as Reinforcing Agents for Bio‐Based Leather‐Like Polymeric Composites: A Review

Cellulose‐based nanomaterials, particularly cellulose nanofibers (CNF) and cellulose nanocrystals (CNC), have been widely explored as reinforcing agents in polymer composites owing to their high aspect ratio, crystallinity, and abundant surface hydroxyl groups. However, their application in bio‐based leather‐like polymeric materials, which require a unique balance of mechanical robustness, durability, and moisture tolerance, remains insufficiently systematized. This review critically examines the translatability of CNF and CNC reinforcement strategies to sustainable leather substitutes derived from bacterial cellulose (BC), plant fibers, and other bio‐resources, with a focus on addressing key performance limitations such as low mechanical strength, dimensional instability, and poor durability. Particular emphasis is placed on structure–property relationships governed by dispersion behavior, polymer–filler interfacial interactions, and surface modification strategies in moisture‐sensitive and multiphase systems. Unlike existing reviews that primarily address nanocellulose reinforcement in general polymer composites, this work adopts an application‐driven perspective tailored to leather‐like materials. In addition to discussing reinforcement mechanisms, the review considers scalability, multifunctionality, and economic feasibility, while explicitly acknowledging current limitations, including the scarcity of direct studies on leather‐like systems and long‐term durability data. By defining both opportunities and constraints, this review proposes a practical material design framework for the development of next‐generation, high‐performance, and environmentally responsible leather alternatives.