OH groups in boralites

Abstract

Four kinds of OH groups (3740,3720,3680 and 3460 cm^–1) are present in H-boralites. The 3740 and 3720 cm^–1 OH groups were previously assigned to silanol, Si—OH, and acidic B⋯HO—Si groups. The results obtained in the present study suggest that both 3680 and 3460 cm^–1 OH groups were formed by the hydrolysis of B—O—Si bond upon ionic exchange in an acidic NH₄Cl solution. The broad 3460 cm^–1 band was attributed to O⋯H—O—Si groups forming the hydrogen bond,m and the 3680 cm^–1 band to B—OH groups in [graphic omitted] fragments. The OH groups in these fragments are unstable and prone to dehydroxylation.