The invention related to a material that can stably hold an imide anion (NH2−) therein even in the atmosphere or in a solvent, and a method for synthesizing the material and a use of the material. A mayenite-type compound into which imide anions are incorporated at a concentration of 1×1018 cm−3 or more are provided. The mayenite-type compound can be produced by heating a mayenite-type compound including electrons or free oxygen ions in a cage thereof, in liquefied ammonia at 450 to 700° C. and at a pressure of 30 to 100 MPa. The compound has properties such that active imide anions can be easily incorporated into the compound and the active imide anions can be easily released in the form of ammonia from the compound, and the compound has chemical stability.