Compositions are disclosed herein comprising poly alpha-1,3-glucan or poly alpha-1,3-1,6-glucan polymer having an open-cell pore structure with an average pore size of about 100 nm to about 3000 nm in diameter. Such polymers have enhanced aqueous liquid absorption capacity, and can be comprised in various products having aqueous liquid absorption function. Methods of preparing glucan polymers of the compositions provided herein are also disclosed.