Operating temperatures affect direct air capture of CO₂ in polyamine-loaded mesoporous silica

Direct air capture (DAC) is a representative negative emission technology that plays a critical role in achieving carbon neutrality. Understanding the CO₂ capture performance of DAC materials in a real-world environment is important to optimize the performance of DAC processes, unfortunately, little is known about their capture efficiency under varying operating temperatures. To this end, we investigated the influence of operating temperatures on the DAC performance of the polyamine-loaded mesoporous silica. We revealed that the CO₂ adsorption selectivity of polyethylenimine-loaded mesoporous silica decreases with reduced adsorption temperatures below 15 ℃. We also parametrically studied the adsorption kinetics, long-term stability, and optimal desorption temperatures ranging from 90 to 120 ℃. Our finding shows that a polyamine loading of 50 wt% in tetraethylenepentamine-loaded mesoporous silica exhibits an outstanding capture capacity of 2.30 mmol CO₂/g in a wide range of adsorption temperatures under simulated air. Furthermore, we also demonstrated that the Avrami model could provide a robust prediction for the adsorption and desorption kinetics of polyamine-loaded mesoporous silica even at low temperatures.