Low temperature performance is key for catalysts used in selective catalytic reduction of NOx with ammonia (NH3-SCR). The best performing NH3-SCR catalysts are based on small pore copper loaded zeolites. A key question remains which structural and compositional parameters make a copper zeolite catalytically active in this application. In this work a collection of 83 different zeolite samples having 25 different frameworks and compositional variations was evaluated to uncover the critical structural and compositional parameters governing catalytic activity at 150 degrees C. The Si/Al ratio, the content of double six-ring building units, the framework density and pore dimensionality were identified as having a strong impact on the catalytic activity of zeolites. A critical value for each of these parameters was determined. This knowledge was used to predict MOZ, SZR and GME as active NH3-SCR catalysts. They were synthesized respecting the compositional prerequisites and their catalytic evaluation confirmed the predicted high catalytic activity. (C) 2020 Elsevier Inc. All rights reserved.