A novel complex [Ba(5-OH–BDC)(H 2 O) 3 ] [5-OH–H 2 BDC=5-hydroxyisophtalic acid] was synthesized and characterized by X-ray crystallography. The complex is Monoclinic P2 1 /c, a=11.1069(4), b=14.8192(6), c=6.5005(2)Å, β=103.465(3)° and Z=4, which exhibits a three-dimensional framework formed by linkage of adjacent two-dimensional (6, 3) layers via intermolecular hydrogen bonds. The title complex has been studied by IR spectrum and TG–DTG. The constant-volume combustion energy of the complex, Δ c U, was determined as being (−3210.45±1.41)kJmol −1 by a precise rotating-bomb calorimeter at 298.15K. The standard enthalpy of combustion, ΔcHmθ, and the standard enthalpy of formation, ΔHmθf, were calculated as being (−3207.97±1.41) and (−1922.80±1.76)kJmol −1 , respectively. A calculation model for determining the specific heat capacity of the complex with an improved RD496-III microcalorimeter is also derived. The specific heat capacity of the complex was (6158.387±0.187)Jmol −1 K −1 .