CoCu-based catalysts are widely used in CO_x hydrogenation reactions to produce higher alcohols due to the C-C coupling ability of Co and the ability of Cu to produce alcohols. This work describes the role of easily happened CO₂ dissociation on the CoCu surface during the reaction, using different silica support to tune the metal—support interaction, and reaches different selectivity to ethanol. CoCu supported on mesoporous silica MCM-41 shows ethanol selectivity as high as 85.3%, and the ethanol space-time yield (STY) is 0.229 mmol/(g_metal·h), however, poor selectivity to ethanol as low as 28.8% is observed on CoCu supported on amorphous silica. The different selectivity is due to the different intensities of CO₂ dissociation on the catalysts. The adsorbed O^⋆ produced via CO₂ dissociation can occupy the cobalt hollow sites on CoCu surfaces, which are also the adsorption sites of C₁ intermediates for further C-C coupling.