Monolithic Zirconium-based Metal-Organic Frameworks for Energy-Efficient Water Sorption Applications

Space cooling and heating, ventilation, and air conditioning (HVAC) accountsfor roughly 10% of global electricity use and are responsible for ca. 1.13gigatonnes of CO2emissions annually. Adsorbent-based HVAC technologieshave long been touted as an energy-efficient alternative to traditionalrefrigeration systems. However, thus far, no suitable adsorbents have beendeveloped which overcome the drawbacks associated with traditional sorbentmaterials such as silica gels and zeolites. Metal-organic frameworks (MOFs)offer order-of-magnitude improvements in water adsorption and regenerationenergy requirements. However, the deployment of MOFs in HVACapplications has been hampered by issues related to MOF powderprocessing. Herein, three high-density, shaped, monolithic MOFs (UiO-66,UiO-66-NH2, and Zr-fumarate) with exceptional volumetric gas/vapor uptakeare developed - solving previous issues in MOF-HVAC deployment. Themonolithic structures across the mesoporous range are visualized usingsmall-angle X-ray scattering and lattice-gas models, giving accuratepredictions of adsorption characteristics of the monolithic materials. It is alsodemonstrated that a fragile MOF such as Zr-fumarate can be synthesized inmonolithic form with a bulk density of 0.76 gcm-3without losing anyadsorption performance, having a coefficient of performance (COP) of 0.71with a low regeneration temperature (≤100°C).