Crosslinked polymers made up of polymerized units of phenothiazine, pyrrole, and aldehyde. The crosslinked polymers are porous with a BET surface area in the range of 300-600 m2/g. A method of synthesizing the crosslinked polymers is described. Processes for using the crosslinked polymers as adsorbent materials for adsorbing gases (e.g. CO2 capturing), and separating fluid mixtures under dry and wet conditions are also introduced.