Ir/SiO2 as a highly active catalyst for the selective reduction of NO with CO in the presence of O2 and SO2.

Coexisting SO2 considerably enhanced the catalytic activity of Ir/SiO2 for NO reduction with CO in the presence of O2 because of the formation of a cis-type coordinated species of NO and CO to one iridium atom ([formula: see text]), a possible reaction intermediate leading to N2 formation.