  Moisture-capturing hydrogels have emerged as attractive sorbent materials
capable of converting ambient humidity into liquid water. Recent works have
demonstrated exceptional water capture capabilities of hydrogels, while
simultaneously, exploring different strategies to accelerate water capture and
release. However, on the material level, an understanding of the intrinsic
transport properties of moisture-capturing hydrogels is currently missing,
which hinders their rational design. In this work, we combine absorption and
desorption experiments of macroscopic hydrogel samples in pure-vapor with
models of water diffusion in the hydrogels to demonstrate the first
measurements of the intrinsic water diffusion coefficient in hydrogel-salt
composites. Based on these insights, we pattern hydrogels with micropores to
significantly decrease the required absorption and desorption time by 19% and
72%, respectively, while reducing the total water capacity of the hydrogel by
only 4%. Thereby, we provide an effective strategy towards hydrogel material
optimization, with a particular significance in pure-vapor environments.
