Provided is a catalyst composition comprising a small pore molecular sieve, about 0.5-5 weight percent of a transition metal (TM) selected from copper and/or iron, based on the total weight of the zeolite, and about 0.5-5 weight percent nickel, based on the total weight of the molecular sieve, wherein the transition metal and nickel are present in a TM:Ni ratio of about 10:1 to about 1:2. Also provided is a synthesis method for preparing a small pore molecular sieve having both Cu and Ni incorporated in situ. Also provided is a method for using such a catalyst for selectively reducing NOx in an exhaust gas.