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In this work, we have successfully developed a novel approach to epoxy foaming using CO2 as the latent blowing agent. The active amine groups of a commercially available curing agent for epoxy resin are blocked by CO2 to obtain ammonium carbamate. The prepared ammonium carbamate can be decomposed by heating. Above 100 °C, CO2 is released from the amine groups and acts as the blowing agent, while the amine compound is used as the curing agent and cures the epoxy resin. The ammonium carbamate combines the functionalities of latent blowing agent and curing agent. The one-pack epoxy foaming formulation has good storage stability under ambient conditions. The thermoset epoxy foams prepared from the one-pack formulation have low density, good mechanical properties, and thermal stability, competitive with the epoxy foams prepared by other methods. This novel approach is simple, environmentally benign, and cost-effective, which represents a promising direction in the development of epoxy foaming technologies.