A combined experimental and simulations assessment of CO2 capture and CO2/H2 separation performance of aminosilane-grafted MCM-41 and pore-expanded MCM-41

Amine-functionalized mesoporous silica materials have attracted considerable attention as robust adsorbents for large-scale CO2 capture and direct air capture (DAC). Amine grafting increases selective affinity at low pressures, yet also often reduces the adsorbent's pore volume and surface area, affecting the kinetics and capacity upon CO2 adsorption. MCM-41 and pore-expanded MCM-41 (PE-MCM-41) were developed here, functionalized using 3-aminopropyl triethoxy silane (APTES), and comparably evaluated for their carbon capture performance at different conditions by a combinational experimental, equilibrium and kinetic modelling, and molecular simulations approach. In specific, CO2 adsorption capacity, CO2/N2 selectivity, CO2 adsorption at humid conditions, heat of adsorption, and regeneration/cyclability were assessed, coupled to molecular simulation insights on the physisorption and chemisorption contribution to the overall adsorption uptake. Indicatively, a capacity value of 3.07 and 2.44 mmol/g was obtained for APTES-PE-MCM-41, and 2.27 and 1.89 mmol/g for APTES-MCM-41, under wet and dry conditions, respectively. The CO2 selective adsorption from H2 rich gas streams was also examined over APTES-MCM-41 in order to assess the potential application in H2 stream purification process. The latter is of high significance in order to use hydrogen as fuel e.g. in anion exchange membrane fuel cells for power production since the presence of CO2 in the feed composition is considered a major drawback in their commercialization.