Two pure borophosphates microporous materials, K[ZnBP2O8] and NH4[ZnBP2O8], have been synthesized and characterized by XRD, FT-IR, DTA-TG techniques and chemical analysis. The molar enthalpies of solution of K[ZnBP2O8](s) and NH4[ZnBP2O8](s) in 3 mol.dm(-3) HCl(aq), of KCl/NH4Cl(s) in (HCl + H3BO3)(aq), and of Zn(PO3)(2)(s) in (HCl + H3BO3 + KCl/NH4Cl)(aq) were measured by microcalorimeter at T = 298.15 K, respectively. With the incorporation of the previously determined enthalpy of solution of H3BO3(s) in 3 mol.dm(-3) HCl(aq), together with the use of the standard molar enthalpies of formation for Zn(PO3)(2) (s), KCl(s), NH4Cl(s), H3BO3(s) and H2O(l), the standard molar enthalpies of formation of.(3184.0.1.2) kJ.mol.1 for K[ZnBP2O8] and.(3067.6.1.2) kJ.mol.1 for NH4[ZnBP2O8] at T = 298.15 K was obtained on the basis of the appropriate thermochemical cycles. (C) 2013 Elsevier Ltd. All rights reserved.