The pure hydrated metalloborophosphate sample, Na-2[CuB3P2O11(OH)]center dot 0.67H(2)O, has been synthesized and characterized by XRD, FT-IR. DTA-TG techniques, and chemical analysis. The molar enthalpies of solution of Na-2[CuB3P2O11(OH)]center dot 0.67H(2)O(s) in 1 mol.dm(-3) HCl (aq), of Cu(OH)(2) (s) in (HCl + H3BO3) (aq), and of NaH2PO4 center dot 2H(2)O (s) in (HCl + H3BO3+ Cu(OH)(2)) (aq) were measured, respectively. With the incorporation of the previously determined enthalpy of solution of H3BO3 (s) in 1 mol.dm(-3) HCl (aq), together with the use of the standard molar enthalpies of formation for NaH2PO4 center dot 2H(2)O (s), Cu(OH)(2) (s), H3BO3 (S), and H2O (I). the standard molar enthalpy of formation of -(4988.4 +/- 2.5) kJ mol(-1) for Na-2[CuB3P2O11(OH)]center dot 0.67H(2)O at T = 298.15 K was obtained on the basis of the appropriate thermochemical cycle. (c) 2011 Elsevier Ltd. All rights reserved.