A clean, safe, and efficient method for the N-carboxyalkylation of lactams was designed and studied in the current report. This three-component coupling of the substrate, carbon dioxide and an alkyl halide, has been developed as a green alternative to phosgene and chloroformates, and takes place at ambient temperature and low pressure of CO2. This provided an improved protocol for the protection of cyclic amides and other functional groups and allowed the obtention of non-classical N-carboxyalkyl derivatives for which the corresponding chloroformates are not accessible or commercially available. The model reaction was successfully performed with car diesel engine emissions and opens the way for new perspectives of carbon capture and use solutions.