Engineering defective MOF-801 nanostructures on the surface of a calcium alginate aerogel for efficient and stable atmospheric water harvesting

Abstract

Global water scarcity, exacerbated by population growth and environmental contamination, makes it imperative to enhance access to water resources. The accelerated evolution of atmospheric water harvesting (AWH) technology presents a valuable opportunity to confront this challenge. Herein, we report a novel solar-driven porous and hygroscopic polypyrrole (PPy)/MOF-801-G/calcium alginate (CA) (PMC) aerogel with a large specific surface area and abundant defect structures. It was shown that the water sorption property of the PMC aerogel was positively correlated with the content of Zr–OH with hydrophilic groups. Moreover, the heat of water adsorption (Q_st) of the P0.5MC aerogel (PMC aerogel with 0.5 g of MOF-801-G) was higher than that of MOF-801-G. P0.5MC exhibited excellent water sorption capacity (0.386 g g⁻¹ at 25 °C and 20% RH) and fast solar desorption efficiency and rate. As a proof-of-concept application, the P0.5MC aerogel was further evaluated for collecting water from the air in a homemade outdoor atmospheric water harvesting device. Under outdoor conditions of 32.85 °C and 61.01% RH, 1.081 kg_H2O/kg_P0.5MC of clean water meeting the World Health Organization (WHO) drinking water standards could be collected in one day. This study provides a strategy to improve sorption capacity by engineering defects as sorption sites and explores the relationship between Zr–OH and hygroscopic properties, paving a new path to improve the working capacity of MOF-801 as a water adsorbent.