Background Covalent organic frameworks (COFs) are crystalline porous materials assembled from organic building units through covalent bonds. Their molecularly tunable skeletons, pore structures, and interfacial functionalities make them an ideal designable platform for the selective removal of pollutants from complex water matrices.

Scope This review focuses on the structure-performance relationships of COFs in water treatment, systematically analyzing the synergistic effects of building units, linkages, topologies, and metal sites on pore microenvironments, framework stability, and electronic structures. Particular attention is given to how these structural elements collectively determine mass transfer, selectivity, and stability.

Synthesis and Shaping Solvothermal synthesis, interfacial polymerization, and electrochemical methods are discussed not as isolated topics but as a means to realize structural regulation and material shaping. Their effects on crystallinity, defect formation, film thickness and continuity, and scalability are compared. Solvothermal routes favor highly crystalline powders through reversible bond exchange and defect correction; interfacial polymerization confines framework growth to phase boundaries and facilitates the formation of thin, continuous selective layers; electrochemical methods regulate monomer activation, migration, nucleation, and film growth on conductive substrates. The applicability of these methods is discussed according to the intended material form and structural requirements to address trade-offs among structural quality, preparation efficiency, material form, and scale-up potential.

Mechanisms and Applications Furthermore, for adsorption, membrane separation, and photocatalytic/electrocatalytic processes, the mechanisms by which structural regulation governs water-treatment performance are elucidated from three perspectives: pore accessibility and interfacial recognition, sub-nanometer channels and selective mass transfer, and electronic structures and active sites. Specifically, for adsorption, binding-site accessibility, pollutant affinity, competitive adsorption, and regeneration stability are evaluated. For membrane separation, effective pore size, interlayer stability, nonselective defects, chemical recognition, permeability, and selectivity are emphasized. For catalysis, framework conjugation, active-site coordination, charge transfer, reactive-species generation, mineralization, energy consumption, and intermediate-product toxicity are considered.

Novelty Unlike existing reviews that often treat structural regulation, synthesis, and applications separately, this review establishes an integrated chain from molecular-level structural regulation to synthesis realization, process evaluation, and engineering constraints, proposing structure-design criteria for different water-treatment processes.

Perspectives Practical application remains limited by long-term stability in complex water matrices, scalable preparation, material shaping, and environmental safety. To address these bottlenecks, future research should focus on hydrolysis-resistant frameworks, low-solvent continuous synthesis with solvent recovery, scalable shaping and membrane fabrication, control of metal leaching, and continuous-flow evaluation in real water samples under representative variations in pH, ionic strength, and natural organic matter. These directions are expected to guide the engineering selection and process matching of COF-based water-treatment materials and to support the development of next-generation sustainable water-treatment technologies.