A microcapsule comprising a chemical skeleton with at least one ligand attached to the chemical skeleton. The chemical skeleton is placed within a capsule. The capsule can then separate a substance from a mixture. The capsule is placed within the mixture and the substance is allowed to enter the capsule. The substance binds to the ligand and cannot escape the capsule. The capsule is then removed from the mixture, thus removing the substance. The preferred embodiment envisions the use of the capsule to remove substances from animal digestive systems.