Improving the selectivity of polymer-based membranes for water treatment while maintaining high water permeability can be achieved through several strategies. These strategies involve modifying the membrane material, structure, and surface properties to enhance the separation performance. Here are some approaches to consider:1. Use of advanced materials: Employ novel polymers with intrinsic microporosity PIMs or polymers with high free volume, which can provide high permeability and selectivity. Additionally, incorporating materials like metal-organic frameworks MOFs or zeolites into the polymer matrix can improve selectivity without compromising permeability.2. Thin film composite TFC membranes: Develop TFC membranes with a thin, selective layer on top of a porous support layer. The thin selective layer provides high selectivity, while the porous support layer ensures high permeability.3. Surface modification: Modify the membrane surface by grafting or coating with hydrophilic materials, such as polyethylene glycol PEG or zwitterionic polymers. This can enhance the membrane's affinity for water, improving both selectivity and permeability.4. Nanocomposite membranes: Incorporate nanoparticles, such as carbon nanotubes, graphene oxide, or metal nanoparticles, into the polymer matrix. These nanoparticles can improve the membrane's selectivity by providing additional transport pathways or by adsorbing specific contaminants.5. Membrane morphology control: Optimize the membrane fabrication process, such as phase inversion or interfacial polymerization, to create a well-defined and controlled porous structure. This can lead to improved selectivity and permeability.6. Post-treatment techniques: Apply post-treatment techniques, such as annealing or solvent extraction, to remove residual solvent or to enhance the membrane's structural stability. This can improve the membrane's selectivity and permeability.7. Mixed matrix membranes MMMs : Combine the advantages of both organic polymers and inorganic materials by incorporating inorganic fillers e.g., zeolites, MOFs, or nanoparticles into the polymer matrix. This can enhance the membrane's selectivity and permeability by providing additional transport pathways or by adsorbing specific contaminants.8. Stimuli-responsive membranes: Develop stimuli-responsive membranes that can change their properties in response to external stimuli, such as temperature, pH, or light. This can allow for tunable selectivity and permeability, depending on the specific application.By implementing these strategies, it is possible to improve the selectivity of polymer-based membranes for water treatment while maintaining high water permeability. This will lead to more efficient and effective water treatment processes, ensuring clean and safe water for various applications.