Static and Dynamic Adsorptions of Water Vapor by Cyclic [Zr-36] Clusters: Implications for Atmospheric Water Capture Using Molecular Solids

Abstract

A 36-nuclear Zr(IV) cluster based on six [Zr6O4(OH)(4)] units is found to form three different crystal structures depending on synthesis conditions. The cubic phase (ZF-3c) is obtained when the cyclic clusters are interlinked by Na(+)or K(+)ions. In the absence of alkali metal ions, either tetragonal (ZF-3t) or hexagonal (ZF-3h) packing structures are formed. All the solids remain crystalline after evacuation, andZF-3hpossesses a permanent porosity. Upon repeated adsorptions of water vapor, the three different molecular solids comprising the same building blocks turn amorphous; however, overall uptake properties are not deteriorated and reproducible isotherms are observed featuring fast uptake at low relative humidity and unrestricted uptake at RH > 90%. A good reproducibility has also been established in cyclic adsorption-desorption measured under dynamic flow conditions, and, especiallyZF-3tdisplays the working capacity 2.7 times that of zeolite 4A thanks to the fast desorption kinetics.