Enhanced moisture sorption through regulated MIL-101(Cr) synthesis and its integration onto heat exchangers

From residences to industries, cooling processes are energy-intensive yet indispensable. Decoupling the sensible and latent heat loads and delegating the latter to desiccant-coated heat exchangers (DCHEs) permits more energy-efficient cooling. However, the commonplace desiccant - silica gel - has limited water sorption capacity. As a crystalline and water-stable metal-organic framework, MIL-101(Cr) (where MIL stands for Materials Institute Lavoisier) is a promising next-generation desiccant. The current challenges lie in scaling up MIL-101(Cr) production and incorporating it into DCHEs. This work demonstrates how tetraethylammonium hydroxide (TEAOH) is not only less toxic for scaled-up additive-based MIL-101(Cr) synthesis but also produces smaller MIL-101(Cr) particles (40-159 nm) with water uptake capacity up to 1.41 g g-1. Subsequently, TEAOH-MIL-101(Cr) was integrated into heat exchangers using polyvinyl alcohol (PVA) to concurrently bind the cuboctahedral particles and enhance heat and mass transfer. In all three adsorption-desorption cycles, the MIL-101(Cr)/PVA-coated heat exchanger had a gravimetric water uptake twice that of the control silica gel-coated heat exchanger. Moreover, the MIL-101(Cr)/PVA-coated heat exchanger can be regenerated at a desorption temperature of less than 50 degrees C while adsorbing up to 0.91 g g-1 of moisture. Therefore, the MIL-101(Cr)/PVA-coated heat exchanger is feasible for applications in dehumidification and other systems. Through regulated and less toxic MIL-101(Cr) synthesis and superabsorbent polymeric binders, this work reports MIL-101(Cr)-coated heat exchangers with twice the water uptake of the silica gel-coated control towards energy-efficient cooling.

Automated summary

Cooling processes, from residences to industries, require a lot of energy and are essential. This study introduces MIL-101(Cr), a new desiccant, to heat exchangers for more efficient cooling. By improving the synthesis method and using a special binder, the MIL-101(Cr)-coated heat exchanger shows improved water uptake capacity and lower regeneration temperature.