Abstract: A process for the production of a zeolitic material comprising one or more zeolite intergrowth phases of one or more zeolites having a CHA-type framework structure comprising SiO2 and X2O3, and one or more zeolites having an AFT-type framework CT structure comprising SiO2 and X2O3, wherein X is a trivalent element, and wherein said process comprises: (1) preparing a mixture comprising one or more sources for SiO2, one or more sources for X2O3, and seed crystals comprising a zeolitic material, said zeolitic material comprising SiO2 and X2O3 in its framework structure and having a CHA-type framework structure; (2) heating the mixture prepared in (1) for obtaining a zeolitic material comprising one or more zeolite intergrowth phases; and (R) subjecting the zeolitic material obtained in (2) to a procedure for removing at least a portion of X from the framework structure of the zeolitic material.