Here we show that petroleum can be formed efficiently at normal temperatures and pressures from carbon dioxide and activated water. The oxygen nano-bubble containing water was treated with TiO2 catalysis under UV irradiation. The activated water was mixed vigorously with kerosene or light oil and carbon dioxide to form an emulsion. The emulsion gradually separated into a two-phase solution. After phase separation, the volume of kerosene or light oil, depending on which oil was utilized, increased by 5 to 10 %.