GaN@ZIF-8: Selective Formation of Gallium Nitride Quantum Dots inside a Zinc Methylimidazolate Framework

The microporous zeolitic imidazolate framework [Zn(MeIM)(2); ZIF-8; MeIM = imidazolate-2-methyl] was quantitatively loaded with trimethylamine gallane [(CH3)(3)NGaH3]. The obtained indusion compound [(CH3)(3)NGaH3]@ZIF-8 reveals three precursor molecules per host cavity. Treatment with ammonia selectively yields the caged cydotrigallazane intermediate (H2GaNH2)(3)@ZIF-8, and further annealing gives GaN@ZIF-8. This new composite material was characterized with FT-IR spectroscopy, solid-state NMR spectroscopy, powder X-ray diffraction, elemental analysis, (scanning) transmission electron microscopy combined with electron energy-loss spectroscopy, photoluminescence (PL) spectroscopy, and N-2 sorption measurements. The data give evidence for the presence of GaN nanopartides (1-3 nm) embedded in the cavities of ZIF-8, induding a blue-shift of the PL emission band caused by the quantum size effect.