The efficient bioactivation of CO₂ provides an alternative new strategy for producing high value chemicals and fuels. Normally, in vitro activation of CO₂ can be achieved by using formate dehydrogenase (FDH). However, the CO₂ solubility and the activity of commercial FDHCb remain a tough challenge for the efficient bioactivation of CO₂. Here, we report a new “ionozyme” strategy created by using ionic liquids (ILs) as a solvent and enzyme stabilizer, resulting in a 142.3-fold increase in CO₂ conversion over FDHCb. The ionozyme (FDHPa-[CH][Pro]-[TMGH][PhO]) was first developed by combing a discovered novel FDHPa with an efficient synergistic ionic microenvironment. The remarkable performance of this ionozyme is attributed to forming key intermediates [CH][ProCOO] and [TMGH][PhOCOO], stabilizing the enzyme structure with increased solvation structure, and shortening the distance (3.9 Å) between NADH and CO₂ to favor the hydride transfer by facilitating their relative orientation and forming new hydrogen bonds at the active sites. This bioactivation of CO₂ by this specific ionozyme represents ideal starting points for the sustainable carbon cycle.