摘要：

Mesoporous β-Ga2O3 was obtained by calcination at 1073 K of the γ-Ga2O3 polymorph previously prepared by adding aqueous ammonia to an ethanolic solution of gallium nitrate. Nitrogen adsorption–desorption at 77 K showed the β-Ga2O3 sample to have a BET surface area of 40 m2 g1 and a bimodal distribution of pore radii, with maxima at 2.1 and 14 nm. The surface chemistry of this material was studied by FTIR spectroscopy of carbon monoxide adsorbed at liquid nitrogen temperature. Lewis acidity was monitored by the corresponding C–O stretching mode of CO interacting with coordinatively unsaturated Ga3+ ions; main IR absorption bands of Ga3+CO adducts were found at 2218 and 2195 cm1, revealing two types of surface-exposed metal cations. The surface OH groups (which were present in partially hydroxylated β-Ga2O3) gave main O–H stretching bands at 3650 and 3695 cm1. These hydroxy groups were found to have a Brnsted acid character, as revealed by formation of hydrogen-bonded adducts with adsorbed carbon monoxide.

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