Abstract: The present invention is an air cleaner that uses molecular sieves, such as zeolite or other microporous/nanoporous crystalline materials with pore sizes ranging from 4 ? to 20 ?, as a filter to remove contaminant gas. The contaminants are adsorbed into the porous material along with ions clusters, or any other oxidant generated by a generating device within the system. The contaminant gas is then catalytically decomposed in the confined space of the pore. In one embodiment, transition metal is incorporated into the porous material, and a heater is installed to substitute or accompany the oxidant-generating device. When the heater is turned on, the contaminant is decomposed within the pores of the materials with the transition metals acting as catalysts. Ultimately, the non-harmful byproducts are the small sized water molecutes and carbon dioxide molecules. Growth of bacteria is also suppressed under a clean and dry condition.