Ultrafine catalysts of CuB and Me-CuB were prepared, characterized and used for methanol synthesis from CO2/H-2 in the liquid phase under 250 degreesC and 30 bar. The doping of Cr, Zr and Th promoted the dispersion and stability of the resulting catalysts, and facilitated methanol formation. The optimal amount of Cr. Zr or Th doped was about 20 mol% in the salt solution for preparation. In addition, 20% Zr-CuB was more suitable for lower reaction temperatures (<225C) and 20% Cr-CuB for the higher temperatures (>225 degreesC) for the methanol synthesis from CO2/H-2. An appropriate amount of CO in the feed of CO2/H-2, and CO2 in the feed of CO/H-2 enhanced the formation of methanol. The methanol productivities increased with CO concentration up to CO/(CO2+CO)=0.8 for 20% Cr-CuB and 20% Zr-CuB, whereas they increased monotonically up to the feed without CO2 for 20% Th-CuB.