(82h) Molecular-Engineered Thermoresponsive Polymer Desiccants for Energy-Efficient Dehumidification

Humidity management in buildings is essential for occupant comfort, moisture-sensitive manufacturing (e.g., semiconductors), and food preservation, which mainly rely on heating, ventilation, and air-conditioning (HVAC) systems. Humidity control in buildings alone is responsible for 600 million tons of CO₂ emissions annually. Cold surface condensation is one common method utilized for dehumidification in HVAC systems. It requires intensive energy to reach extremely low-temperature setpoints for effective moisture condensation, while also overcooling the air and necessitating additional energy for reheating. To avoid this overcooling process, the desiccant wheels, composed of hygroscopic desiccants such as silica gels, are developed to adsorb moisture from the air directly for dehumidification. However, high thermal energy is required to overcome the enthalpy of vaporization (~2400 J/g) during the regeneration process of the traditional desiccants.

Thermoresponsive polymer (TRP) desiccants, with temperature-dependent moisture sorption properties, offer a promising low-energy alternative. These desiccants have lower critical solution temperatures (LCST) (45 – 60 ℃), allowing moisture absorption below LCST and moisture release in the liquid form above LCST. This approach significantly reduces the energy required for regeneration by bypassing the high vaporization enthalpy. In addition, the relatively low LCST facilitates the use of low-grade thermal energy sources such as industrial waste heat, solar energy, and condenser heat from air conditioners for regeneration, further enhancing sustainability.

In this work, molecular engineering techniques, including chemical composition adjustment and molecular structure modification, have been utilized to incorporate hygroscopic moieties into TRP, creating high-performance TRP desiccants. The resulting materials exhibit tunable LCSTs in a moderate temperature range of 50 ℃ to 60 ℃, high moisture uptake capacity, fast dewatering rates, and excellent mechanical stability—key characteristics for building dehumidification. The dehumidification performance was evaluated using Python modeling, showing up to a 2.26-fold increase in energy efficiency for moisture removal compared to conventional silica gel desiccants. This work represents a significant advance toward reducing energy use and greenhouse gas emissions, contributing to sustainability and climate resilience in building dehumidification.