# Effect of lattice shrinking on the migration of water within zeolite LTA

## TL;DR

This study investigates how lattice shrinking influences water migration within zeolite LTA, revealing that framework composition and pressure determine water's preferred adsorption sites, which vary between hydrophilic and hydrophobic conditions.

## Contribution

It provides new insights into the relationship between framework composition, pressure, and water distribution in zeolite LTA, highlighting the effects of lattice shrinking on water migration.

## Key findings

- Water enters large α-cages in hydrophobic frameworks.
- Water prefers small β-cages in hydrophilic frameworks.
- Framework composition and pressure influence water's adsorption site preference.

## Abstract

Water adsorption within zeolites of the Linde Type A (LTA) structure plays an important role in processes of water removal from solvents. For this purpose, knowing in which adsorption sites water is preferably found is of interest. In this paper, the distribution of water within LTA is investigated in several aluminum-substituted frameworks ranging from a Si:Al ratio of 1 (maximum substitution, framework is hydrophilic) to a Si:Al ratio of 191 (almost pure siliceous framework, it is hydrophobic). The counterion is sodium. In the hydrophobic framework, water enters the large {\alpha}-cages, whereas in the most hydrophilic frameworks, water enters preferably the small $\beta$-cages. For frameworks with moderate aluminum substitution, $\beta$-cages are populated first, but at intermediate pressures water favors $\alpha$-cages instead. Framework composition and pressure therefore drive water molecules selectively towards $\alpha$- or $\beta$-cages.