Figure shows the radii of ions confined in micropores and mesopores, along with the radii of bulk ion pairs and sole H2O (see Method S6 and Tables S8-S10 for details). As salt concentration increases, the number of available water molecules decreases, resulting in a smaller bulk RH. In the larger mesopores, the ions retain a larger RH. An initial decline in inpore radii is observed up to 5 mol•kg⁻¹. Beyond 5 mol•kg⁻¹, however, the in-pore ionic radii exhibit an opposite trend compared to bulk ionic radii, indicating that larger ion-pair sizes restrict partial ion desolvation.