[en] Highlights: • Synthesis of a novel material: doped polymeric CO via hard X-ray photochemistry:${\text{SrC}}_2{\text{O}}_4+\text{h}\upsilon \to {\text{SrCO}}_3+\text{polyCO}$. • The reaction occurs at ambient conditions and at elevated pressure. • The material is very stable and trapped CO₂ inside it at ambient conditions for over one year. • Potential optical and electrical benefits of industrial/technological importance. We report a novel synthesis of stable doped solid carbon monoxide (p-CO) via hard X-ray irradiation of strontium oxalate at ambient conditions and high pressure. We also show via mid- and far- infrared (IR) techniques that CO₂ produced via X-ray photochemistry remained trapped within the recovered sample for many months in contrast to pure p-CO which decomposes in days. Our results demonstrate that p-CO doped with carbonates (as verified with IR and Extended X-ray Absorption Fine Structure spectroscopies) is relatively stable, enabling longer term and practical use of this novel material for CO₂ storage or as a novel electrical/optical material.