Fundamental and perspectives of thermo-responsive materials for dehumidification and water harvesting

Dehumidification and water harvesting require high efficiency technologies. Compared with traditional materials, thermo-responsive materials (e.g., PNIPAM) can achieve low temperature regeneration, due to the lower critical solution temperature (LCST) features. To clarify the water adsorption and releasing performance of thermo-responsive polymers and further propose the potential research of the application in energy field, this paper reviews the existed research for three aspects: synthesis, water adsorption/desorption kinetics and application. Firstly, the grafting of thermo-responsive polymers on traditional materials and modification of thermo-responsive polymers for improving the adsorption/desorption performance is concluded. Secondly, the swelling and shrinking, the interaction with water during adsorption and releasing processes is reviewed. At last, the applications of the water vapor adsorption and water releasing features of thermo-responsive materials in energy field is summarized, including dehumidification, water harvesting, passive cooling and potential improvement for testing devices. Through the literature review, it can be generalized that the thermo-responsive polymer-based adsorbents have high water adsorption capacity and low regeneration temperature requirement, becoming a potential adsorbent for dehumidification and water harvesting. For the water adsorption and desorption, the temperature related heat and mass transfer kinetics requires further research, especially the thermodynamic model. The hybrid thermo-responsive polymer dehumidification and water harvesting units and systems have good application prospect, which requires research for both design and optimization. [Display omitted] •Water adsorption/desorption kinetics of thermo-responsive materials is reviewed.•Application of thermo-responsive materials for energy saving is summarized.•High water adsorption amount, low desorption energy of thermo-responsive materials.•Water adsorption/desorption thermodynamic and heat-mass transfer model is required.•Research on dehumidification and water harvesting unit and systems is recommended.