High-performance and ultra-stable selective catalytic reduction (SCR) catalyst with low-cost is needed for controlling NOx emissions of the Euro 6 diesel vehicle. The combination of copper-tetraethylenepentamine (Cu-TEPA) and morpholine (MOR) as templates allowed the direct synthesis of highly active and hydrothermally stable submicron Cu-SAPO-34 catalyst for SCR of NOx with NH3 (NH3-SCR). It exhibited much better catalytic activity and hydrothermal stability than the reference catalyst synthesized with Cu-TEPA, diethylamine and tetraethylammonium bromide as templates. The origin of superior SCR performance of the submicron Cu-SAPO-34 catalyst was investigated by a series of characterization techniques including XRD, N-2 sorption, NMR, NH3-TPD, H2-TPR, UV-vis-DRS and XPS. Consequently, the structure-performance relationship of the submicron Cu-SAPO-34 catalyst was well established. The isolated Cu2+ ions exist predominantly in submicron Cu-SAPO-34 with a plenty of Si (nOAl) (n = 1-4) structures. These Si coordination structures could generate a large number of Bronsted acid sites, which could be beneficial for NO reduction. The typical cubic crystal and isolated Cu2+ ions remain stable even after steaming at 800 degrees C for 12 h. Furthermore, the amount of isolated Cu2+ ions increase and copper oxides decrease and redistribute after steaming. The NH3-SCR kinetic test further proved the superior NH3-SCR performance of the submicron Cu-SAPO-34 catalyst. (C) 2018 Published by Elsevier B. V.