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The low temperature activity of Fe-loaded zeolites as selective catalytic reduction of NO x by NH 3 (NH 3 -SCR) catalysts is a critical drawback for practical application. Here, we found unexpected improvement of low temperature activity by our proposed post-synthetic treatment. An Al-rich zeolite beta (Si/Al=5) is employed as the catalyst support, and the parent sample is dealuminated for higher hydrothermal stability, followed by the liquid-mediated stabilization treatment and impregnation. It is found that stabilized samples feature excellent low temperature activity and high N 2 selectivity even for a long-term operation, along with the ability to maintain high NO x conversion after aging. The improved SCR activity should be attributed to abundant acid sites in Al-rich framework and better stabilization of monomeric iron species after the stabilization treatment. Furthermore, the low yield of side product N 2 O is probably due to the absence of the generation of NH 4 NO 3 during NH 3 -SCR catalyzed by Fe-loaded zeolites., (© 2023 Wiley-VCH GmbH.)