Assemblable Carbon Fiber/Metal–Organic Framework Monoliths for Energy-Efficient Atmospheric Water Harvesting

Atmospheric water harvesting (AWH) with metal–organic frameworks (MOFs) represents an attractive way to alleviate water shortage stress in arid regions. However, scaling up such a concept has been partially limited by the insufficient development of the highly efficient heating and suitable processing of MOF sorbents for making them more applicable to AWH devices. To overcome these limitations, a commercial carbon fiber (CF) bundle is embedded into an Al-fumarate MOF monolith assisted by a cross-linked sodium alginate (SA) network, resulting in a cylindrical CF/Al-fumarate/SA (CAS) monolith with a coaxial structure. On applying electrical power, the embedded CFs could rapidly generate enormous localized electrical heating (LEH) within a CAS matrix with exceptionally high electrothermal conversion efficiency, thereby triggering the adsorbed water in CASs to be highly efficiently released in an energy-efficient way. In particular, such CAS monoliths can be easily connected to each other in either series or parallel, forming versatile CAS assemblies with well-controlled LEH capacity. Using a serial CAS assembly as atmospheric water sorbents, a newly atmospheric water harvester has been further developed based on an LEH-driven water desorption method. The resulting prototype enables to continuously work for 7.2 water harvesting cycles per day and deliver 1.7 and 1.2 LH2O kgAl-Fum/SA–1 daily water productivity under controlled indoor and outdoor conditions, corresponding to 4.4 and 6.2 kW·h LH2O–1 energy consumption, respectively. Please note that this is the first exploration in the use of flexibly assemblable MOF monoliths and the LEH-driven water desorption method for water production with AWH, demonstrating a promising way to achieve energy-efficient, scalable, low-cost, and industrially favorable AWH in arid areas.