Synthesis, Characterization, and Thermochemical Properties of a Microporous Crystal Material for Rb2[Ga{B50_(10))]·4H2O

摘要

A new microporous galloborate of Rb2[Ga-(BsO_(10))]-4H2O has been synthesized under mild hydro-thermal conditions, which was characterized by chemical analysis, powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR), differential thermal analysis/thermogravim-etry (DTA-TG), and single crystal X-ray diffraction. Its structure possesses a 3D open framework with 11 -ring channels constructed by BsO_(10) clusters and GaO4 units. The enthalpies of solution of RbCl(s), KCl(s), K2[Ga- (BsO_(10))]·4H2O(s), and Rb2[Ga(B5O_(10))]·4H2O(s) in the solvents at 298.15 K were measured, respectively. By using the standard molar enthalpies of formation for RbCl(s), KCl(s), and K2[Ga(B5O_(10))]·4H2O(s), Δ_H_m° of Rb2[Ga(B5_(10))]·4H2O(s) was obtained as -(5762.9 ± 9.1) kJ·mol~(-1) on the basis of the appropriate thermochemical cycle. Moreover, Δ_H_m° ([Ga(B5O_(10))~(2-)) of -(4100.8 ± 9.1) kJ·mol~(-1) has also estimated by a group contribution method, which can be used to predict the standard molar enthalpies of formation of other galloborates containing the [Ga(B5O_9100)]~(2-) anionic framework.