Ordered mesoporous carbon with tunable, unusually large pore size and well-controlled particle morphology

Abstract

A method is proposed to synthesize well-ordered mesoporous carbon with a remarkably wide pore diameter using microwave-synthesized mesoporous silica, MWSBA-15, as the template. The pore size of the carbon is controlled by tuning the pore size of MWSBA-15, which is accomplished by varying the temperature of the hydrothermal treatment, while using the same amount of carbon precursor. Hereby the pore size can be systematically varied between 5 nm and 9 nm, and the pore volume between 1.4 cm³ g⁻¹ and 1.9 cm³ g⁻¹. A specific surface area between 1400 and 1500 m² g⁻¹ is obtained for all mesoporous carbon samples. The data suggest that the material, denoted by MWCMK-3, bears strong structural similarity to CMK-3. In addition, it was noted that the pore size of MWCMK-3 increases when the carbon rod size decreases, which correlates with an increasing distance between the rods. Both the MWSBA-15 and the MWCMK-3 particles have a rod-like morphology, and the particle size distribution exhibits low polydispersity. The merit of microwave synthesis lies in its rapid and homogeneous heating of the reacting mixture to the desired temperature. Hydrothermal treatment to as high as 220 °C was performed on MWSBA-15 to achieve an unusually large pore size and still retain a narrow pore size distribution, which is translated to similar properties in MWCMK-3. A partial breakdown of the ordered structure was observed when using MWSBA-15, hydrothermally treated at 240 °C. Results are backed by N₂ adsorption isotherms, small-angle X-ray scattering, FESEM, and HRTEM images. Ordered mesoporous carbons with large controllable pore diameters are of interest to fuel cells, batteries, supercapacitors, and protein storage, sensing and release.