Covalent Organic Framework Polyamide Nanocomposite Membranes: From Chemical and Structural Regulation to Efficient Water Separation

ABSTRACT Membrane‐based desalination and wastewater reclamation play an important role in addressing the global freshwater crisis. However, state‐of‐the‐art polyamide (PA) composite membranes still suffer from inherent limitations, including the trade‐off between permeability and selectivity, insufficient retention of small neutral solutes, susceptibility to fouling, and poor chemical stability. Covalent organic frameworks (COFs), with their ordered crystalline structure, tunable pore function, and chemical stability, offer unprecedented opportunities for molecular‐level regulation of PA membranes. Introducing COF nanomaterials into PA layers enables the construction of ordered transport channels for rapid water permeation and selective solute sieving. COF fillers also act as interfacial modifiers to regulate monomer diffusion and PA crosslinking during interfacial polymerization, reshaping membrane physicochemical properties. These synergistic effects simultaneously improve water permeance, solute rejection, fouling resistance, and structural stability. Given the rapid advancement of COF nanomaterials, this review summarizes progress in COF‐based PA nanocomposite membranes for water separation, focusing on COF structural design, incorporation strategies, regulatory mechanisms, and the relationship between membrane structure and separation performance. Critical challenges in interfacial chemistry, scalable fabrication, and long‐term stability are discussed, and future research directions toward practical applications are proposed. This review underscores the potential of COF‐based PA nanocomposite membranes for efficient and sustainable water purification.