polymer - metal ion composites and methods are provided for reversibly binding target compounds using such composites . broadly , the composites comprise an amorphous polymer matrix having a plurality of channels with metal ion - ligand complexes immobilized therein . the composites are formed by polymerizing a polymeric moiety with a metal complex template in the presence of a solvent . the template is formed of a metal ion having a ligand bonded thereto as well as to polymer matrix . the metal ion and ligand are selected to yield a composite having a particular chemical and / or physical environment around the metal sites , depending upon the desired end use . preferred metal ions include ions of the transition metals . the composites can be contacted with target compounds for reversibly binding the compounds . exemplary compounds include those selected from the group consisting of oxygen , carbon monoxide , carbon dioxide , compounds having an atom of p , s , or n , and mixtures thereof . the compound can be released from the composites at the desired time and location by heating the compound - containing composite .