Recent advances in porous adsorbent assisted atmospheric water harvesting: a review of adsorbent materials

Abstract

Water shortage is an increasing threat to humankind. Porous sorbent assisted atmospheric water harvesting (psaAWH) has emerged as an effective technological countermeasure. In this review, we summarize the types of porous adsorbents used in psaAWH and provide an overview of their states of development. The water adsorption mechanism and the processes associated with each material are analyzed, and the application prospects of the adsorbents are evaluated. The effect of the inherent properties (pore size, functional group, etc.) of the adsorbent on the water harvesting performance is also discussed. Further, we focus on the water adsorption/desorption kinetics of the adsorbents and outline various methods to improve the kinetics. At this stage, there are many strategies for improving the kinetics of the adsorbent, which in turn influences the adsorption process and intra/inter-crystalline diffusion. However, there is still limited research on the transport of water molecules in microporous adsorbents for psaAWH. Thus, this aspect is re-examined herein from a new perspective (superfluidity) in the review. Based on the discussion, we can reasonably infer that water molecule superfluidity can exist in nanoconfined channels, thus promoting the rapid transport of water molecules. The formation of water superfluidity is a feasible strategy for improving the intracrystalline diffusion of the psaAWH adsorbent. Finally, we consider the future developments and challenges of psaAWH in detail. We think this review can serve as a guide for further research in this ever-expanding field.