Pinpointing the Onset of Water Harvesting in Reticular Frameworks from Structure

Covalent organic frameworks (COFs) have emerged as promising
atmospheric
water harvesters, offering a potential solution to the pressing global
issue of water scarcity, which threatens millions of lives worldwide.
This study presents a series of 2D COFs, including HCOF-3, HCOF-2,
and a newly developed structure named COF-309, designed for optimized
water harvesting performance with a high working capacity at low relative
humidity. To elucidate their water sorption behavior, we introduce
a hydrophilicity index directly linked to intrinsic properties, such
as the strength and spatial density of adsorptive sites. This index
is mathematically correlated to the step of water adsorption isotherms.
Our correlation provides a predictive tool that extends to other microporous
COFs and metal–organic frameworks, significantly enhancing
the ability to predict their onset positions of water adsorption isotherms
based on structural characteristics. This advancement holds the potential
to guide the development of more efficient materials for atmospheric
water harvesting.