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

Abstract

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 °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.