Preparation of N-(3-silicapropyl) imidazolium hydrogen sulfate ([Sipim]HSO4) as a heterogeneous acidic ionic liquid is described. This heterogeneous ionic liquid was used as catalyst for the synthesis of alpha-aminonitriles by a one-pot condensation of aldehydes, amines, and trimethylsilyl cyanide at room temperature. Catalyst could be recycled for several times without any additional treatment.