**3. Conclusions**

Membranes play significant roles in sustainable development, especially Goal 6: clean water and sanitation. It is necessary to consider the developments in membrane technologies in terms of new generation membrane production, module development, and related application areas of technology. Smart membranes can show tunable features based on the condition of the stimulus or stimuli present internally or externally, resulting in improved and desirable controllability over the process of pollutant removal from water. Because of their physicochemical stability, repeatability, and long life, stimuli-responsive smart materials (mainly adsorbents and filtration membranes) have the potential to be key materials for membrane production, particularly in the field of water treatment. Although they have advantages, current smart membranes suffer from complicated and difficult-to-scale-up production processes, low flux, and weak mechanical properties. Smart membranes have a bright future, and it is important to investigate and encourage their development, use, and advancement.

**Author Contributions:** M.Y. and Z.C. contributed equally to this work. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable. **Data Availability Statement:** Data and intellectual property belong to the Istanbul University-Cerrahpasa and Istanbul Gelisim University; any sharing needs to be evaluated and approved by the universities.

**Acknowledgments:** The authors would like to thank the Turkish Academy of Sciences for its support.

**Conflicts of Interest:** The authors declare no conflict of interest.
