Selective catalytic reduction articles and systems

A selective catalytic reduction article comprising a substrate having a front upstream end and a rear downstream end defining a length of the substrate and having a catalytic coating thereon, wherein the catalytic coating comprises:

• a first coating layer comprising a first copper-containing molecular sieve;
• and
• a second, different coating layer comprising a second copper-containing molecular sieve;
• wherein the first copper-containing molecular sieve comprises copper oxide in an amount of about 0.1 wt. % to about 3 wt % based on a total weight of the molecular sieve, the second copper-containing molecular sieve comprises copper oxide in an amount based on a total weight of the molecular sieve, and the amount of copper oxide comprised by the first copper-containing molecular sieve is less than the amount of copper oxide comprised by the second copper-containing molecular sieve;
• wherein the selective catalytic reduction article exhibits a NOx conversion greater than or equal to 92% and a N2O formation less than or equal to 2% when subjected to Heavy Duty Diesel US Federal Test Procedure cycle conditions;
• and
• wherein the first copper-containing molecular sieve has a silica to alumina ratio equal to that of the second copper-containing molecular sieve;
• and
• wherein a ratio of the amount of copper oxide in the first copper-containing molecular sieve to the amount of copper oxide in the second copper-containing molecular sieve ranges from 0.6:3.4 to 2.3:2.7.