Direct Air Capture of CO2 with Metal Nitrate-Doped, Tetraethylenepentamine-Functionalized SBA-15 Adsorbents

Direct air capture (DAC) by solid amine adsorbents is a promising route to mitigate CO2 emissions from distributed sources and confined spaces. However, a capacity-stability trade-off of supported amine adsorbents often exists for DAC applications. Herein, we report that a KNO3-doped, tetraethylenepentamine (TEPA)-functionalized SBA-15 adsorbent (i.e., 50TEPA-4.5K/SBA-15) has a high CO2 adsorption capacity and good cycling stability for DAC. 50TEPA-4.5K/SBA-15 is synthesized by successive impregnation of KNO3 (4.5 wt %) and TEPA (50 wt %) onto SBA-15 and evaluated using a fixed-bed adsorber in cyclic operation (adsorption at 30 degrees C in 440 ppm of CO2 and 50% relative humidity and desorption at 90 degrees C in pure N2). 50TEPA-4.5K/SBA-15 possesses good antioxidation properties; moreover, its CO2 adsorption capacity stabilizes at 5.45 mmolCO2/gadsorbent in 10 consecutive adsorption-desorption cycles, which is much higher than that of 50TEPA/SBA-15 (3.64 mmolCO2/gadsorbent) and also outperforms that of TEPA-functionalized adsorbents in the literature. This study provides new opportunities to develop high-performance solid amine adsorbents for DAC applications.

Automated summary

This study reports a KNO3-doped, tetraethylenepentamine (TEPA)-functionalized SBA-15 adsorbent with high CO2 adsorption capacity and good cycling stability for DAC applications. The adsorbent possesses good antioxidation properties and outperforms similar adsorbents in terms of CO2 adsorption capacity.