Synthesis of nitrogen-rich nanoporous carbon materials with C3N-type from ZIF-8 for methanol adsorption

Abstract

The N-rich nitrogen (25.7%) porous carbon with high surface area was prepared by using N-rich ZIF-8 as a template and precursor and urea as a secondary nitrogen source. Simple pyrolysis of the ZIF-8/urea composite leads to N-rich carbon with C3N-type stoichiometry. The content and type of nitrogen functional groups can be tunable by the pyrolysis temperature. The resulting carbons stand out by a highly polarizable microporous structure and thus high affinity for methanol adsorption. The experimental results indicate that the microporous structure of porous carbon is the determinant of methanol adsorption at high pressure, whereas at low pressure, the methanol adsorption dominantly depends on the nitrogen functional groups. To more deeply investigate the interactions between the methanol molecules and carbon framework, we performed the theoretical analysis regarding the adsorption isotherms, binding energy and atomic partial charge using the GCMC and DFT methods. The methanol adsorption capacity is determined by the electrostatic interaction at low relative pressures due to the nitrogen functional groups enhancing the electrostatic potential of carbon surface. While the dispersive interaction becomes dominant at high relative pressures, and thus the methanol adsorption mainly depends on the porosity structure.