The in situ FT-IR spectra were used to study the CO2 hydrogenation reactions over the SiO2-supported heterobinuclear metal complex catalysts, RhM (M = Cr, Mo, W). The bands, which correspond to the formate species adsorbed on the catalysts, were observed. During the hydrogenation reactions, the adsorbed linear and bridged bridging CO were not observed. The experimental results suggest that for the CO2 and CO hydrogenation reactions over the same catalysts, their catalytic active intermediate species and the reaction mechanisms should be different.