Microwave-assisted post-synthetic detemplating method was applied to remove successfully the occluded organic template from the mesoporous silica frameworks of as-synthesized SBA-15 within a short period of time compared to a conventional method, such as furnace calcination. The nitrogen adsorption/desorption isotherm studies showed that the resultant detemplated SBA-15 had a very high specific surface area of 1,271m2/g, large pore size of 9.21 nm and high pore volume of 2.10 cm3/g; while the powder X-ray diffraction patterns and high-resolution TEM images of these support materials revealed the presence of highly ordered mesopores without any structural shrinkage. Both the microwave power and time during post-synthetic microwave irradiation were found to influence the morphological structure of the SBA-15 support. To evaluate the adsorption performance of the microwave-irradiated SBA-15 support, CO2 adsorption uptake was measured after functionalizing it with different loadings of polyethyleneimine (PEI) under 9.7% CO2/N2 mixture at 75 °C. The maximum CO2 uptake was 3.63mmol CO2/g (0.16 g/g), with an optimum PEI loading of 70 wt%. Because of the significant improvement in structural characteristics, the microwave-irradiated SBA-15 supports facilitated more PEI incorporation that contributed to about 15% higher CO2 uptake than that of conventional furnace calcined one. In addition, the sorbent demonstrated very good cyclic stability when tested over 25 cycles and for a total duration of 20 h in humid conditions.