Described is a copper containing ZSM-34, OFF and/or ERI zeolitic material having a silica to alumina mole ratio ranging from about 4 to about 50 and a copper content, reported as CuO, ranging from about 1 to about 10 wt.-%, based on the total weight of the calcined zeolitic material, and having an alkali metal content, reported as the metal oxide, ranging from about 0.7 to about 1.5 wt.-%, wherein the 750° C.-aged copper containing ZSM-34, OFF and/or ERI zeolitic material exhibits NO conversion at 200° C. of at least about 75% and at 450° C. of at least about 90%, measured at a gas hourly volume based space velocity of 30000 h−1 under steady state conditions at maximum NH3-slip conditions in a gas mixture of 500 ppm NO, 500 ppm NH3, 10% O2, 5% H2O, balance N2.