Morphological control of mesoporous CN based hybrid materials and their excellent CO2 adsorption capacity

Abstract

Highly ordered mesoporous carbon nitrides (MCN-1-Ts) with uniform rod shaped morphology have been synthesized by a hard templating technique using SBA-15 silicas prepared a under hydrothermal "static" condition at different temperatures as templates following a simple polymerization reaction between carbon tetrachloride (CTC) and ethylenediamine (EDA) inside the large pores of SBA-15. The static hydrothermal condition offers uniform rod shaped morphology for the template materials which has been completely replicated into the MCN nanostructures. The obtained materials were characterized with low angle XRD, N-2 adsorption, high resolution transmission electron microscopy, high resolution scanning electron microscopy (FE SEM), Fourier transform infra-red (FT-IR), and X-ray photoelectron spectroscopy (XPS). The characterization results confirm the successful replication of the ordered structure, morphology and mesoporosity of the template material into carbon nitride. The FT-IR and XPS techniques confirm the presence of free -NH and -NH2 groups on the surface of MCN, which are critical for capturing CO2. Finally, these materials with high surface area and uniform morphology are used as adsorbents for high pressure CO2 adsorption at different temperatures of 0, 10 and 25 degrees C. It is found that the morphology of the materials which has a direct relation with the textural parameters plays a significant role in enhancing the amount of CO2 adsorption. The MCN with the uniform morphology and the highest surface area registers the highest CO2 adsorption capacity (16.5 mmol g(-1)) at 0 degrees C and 30 bar pressure, which is found to be higher than that of the previously reported 3D- cage type MCN, activated carbon, multiwalled carbon nanotubes and mesoporous silicas.