Theoretical Study on the Polymerization Mechanism of Hydrogen-Doped Carbon Monoxide under High Pressure

Carbon monoxide (CO), as a prototypical low-Z molecular system, can polymerize under high pressure to form polymeric carbon monoxide (p-CO). The polymerization mechanisms and structures are of fundamental importance for understanding pressure-induced bonding and exploring novel functional materials. However, progress in this field has been hindered by two major challenges: the high-pressure requirements for CO and the metastable property of p-CO at ambient pressure. Recent studies have shown that hydrogen (H₂) doping can facilitate the polymerization of CO, but the polymerization mechanisms and structures are still poorly understood. In this work, molecular dynamics simulations were performed to investigate the influence of H₂ on the polymerization progress of CO. The results reveal that a doping ratio of 10% can optimally reduce the polymerization pressure of CO. At 3–4 GPa, H₂ physically induces the dimerization reaction of CO. At 5 GPa, the chemical inertness of H₂ inhibits further polymerization of CO. When the pressure reaches 10 GPa, H₂ participates in the polymerization reaction, forming C―H and O―H bonds. Finally, the polymerization produces a disordered three-dimensional network structure (p-CO/H) dominated by C―C and C＝O bonds.