Facile synthesis of MOF-5-derived porous carbon with adjustable pore size for CO2 capture

In this study, a facile strategy is reported for the preparation of porous carbon materials with adjustable pore size through carbonization of MOF-5 at 900 ​°C with the assistance of different additives. Results show that the physical and chemical properties (such as morphology, carbon defect content, BET specific surface area, pore structure) of the porous carbon materials can be adjusted through introduction of different compounds (i.e., C16H32O2, C6H14O6, C18H36O2, Na2CO3, KOH, Cu(NO3)2, NaCl, KCl, MgCl2, ethyl cellulose) during the carbonization processes. CO2 adsorption experiment results show that there is a linear relationship between the CO2 adsorption capacity (at 25 ​°C and 0.15 ​bar) and the cumulative pore volume of pores at 5–7 ​Å, suggesting that pores in the range of 5–7 ​Å play a major role in CO2 adsorption at such condition. While the CO2 adsorption capacity (at 25 ​°C and 0.15 ​bar) is independent on the BET specific surface area of the materials. Among the prepared porous carbon materials, 5C–C6H14O6-900 exhibits the highest CO2 adsorption capacity (i.e., 3.32 ​mmol/g at 25 ​°C and 1 ​bar, 0.88 ​mmol/g at 25 ​°C and 0.15 ​bar), with good adsorption/desorption cycle stability and CO2/N2 selectivity. Our work provides a facile and general method to adjust and control the pore size distribution of MOF-derived porous carbon materials. Besides, the analysis results indicate that the micropores in a specific pore size range play a decisive role in the adsorption of CO2 at low pressure, which provides a new idea for the preparation of high-efficiency adsorbents at low pressures.