Copper benzene@1, 3, 5-tricarboxylate (Cu@BTC) metal organic frameworks with two mixed phases (Cu-3(BTC)(2 center dot)3H(2)O + {[Cu(BTC-H-2)(2)center dot(H2O2] center dot 3H(2) O}) are synthesized in water solvent at different temperatures. The crystalline nature, porosity and morphology of prepared products are characterized by X-ray diffraction, Brunauer-Emmett-Teller surface analyzer and transmission electron microscope, respectively. The formation mechanism of these two mixed phases has been proposed, and the electrochemical measurements of the Cu@BTC MOFs are carried out for electrode material of supercapacitors. The Cu@BTC-120 electrode shows significant enhancement of specific capacitance compared with other Cu@BTC electrodes. A maximum specific capacitance of 228 F g(-1) has been obtained at a current density of 1.5 A g(-1) and long cyclic stability up to 3000 cycles with capacitance retention of similar to 89.7% has been achieved for Cu@BTC-120 electrode. The fast transportation of the electrolyte ions in substantial voids space between octahedral micro-crystals (Cu-3(BTC)(2)center dot 3H(2)O) and micro-rods ({[Cu(BTC-H-2)(2)center dot(H2O2 center dot 3H(2)O}) of Cu@BTC-120 has greatly improved the electrochemical performance.(C) 2017 Elsevier B.V. All rights reserved.