Thermodynamic properties of microporous crystals for two hydrated borogermanates, K2[Ge(B4O9)]·2H2O and K4[B8Ge2O17(OH)2]

► Two borogermanates for microporous crystals were synthesized and characterized. ► 1 mol · dm−3 NaOH (aq) was selected as the solvent. ► The enthalpies of solution of title two microporous crystals were measured. ► The enthalpies of solution of K2B4O7·4H2O(s) and GeO2(s) were measured. ► ΔfHmo for title two microporous crystals were obtained by a thermochemical cycle.