Y3+- and La3+-doped zeolitic imidazolate frameworks-8 (ZIF-8) crystals were first successfully prepared by hydrothermal synthesis. As-synthesized crystals were investigated by X-ray diffraction, field-emission scanning electron microscope, fluorescence spectrometric titration, and gas adsorption measurement. The Y3+-doped ZIF-8 crystals were found to be highly sensitive to amines (ethylamine, diethylamine, and triethylamine), providing a novel candidate for the sensitive and rapid detection of amines.