Engineering Amine-Containing Adsorbents for Efficient Carbon Dioxide Capture in Closed-Circuit Escape Respirators.

In emergencies involving oxygen deficiency or exposure to toxic gases, closed-circuit escape respirators (CCERs) provide prompt and reliable respiratory protection, enabling safe escape from hazardous environments. These devices utilize a self-contained system that recycles exhaled breath by scrubbing CO2 and replenishing O2. CCERs require efficient CO2 adsorbents, as excessive CO2 accumulation from exhalation can lead to hypercapnia, causing dizziness, confusion, or even loss of consciousness. This study demonstrates that 1,2-epoxybutane-functionalized polyethylenimine supported on gamma alumina (EB-PEI/γ-Al2O3) is a very promising CO2 adsorbent for CCERs, significantly outperforming the conventionally used soda lime. By controlling 1,2-epoxybutane functionalization, the heat of CO2 adsorption can be precisely tuned, enabling the adsorbent to efficiently capture CO2 from exhaled breath (5% CO2 and 3% H2O) while minimally adsorbing CO2 from ambient air (400 ppm of CO2 and 1.5% H2O). This desirable CO2 adsorption window allows the CCER device to be stored long-term under ambient conditions without cumbersome airtight packaging and enables the CO2-saturated adsorbent to be regenerated through simple air exposure at room temperature. The adsorbent also exhibits remarkably faster CO2 adsorption kinetics and generates less heat and moisture compared to soda lime, thereby enhancing user comfort and safety.