Nitrogen and oxygen codoped porous carbons (NOCKs) were obtained by nitrogenization, preoxidation, and chemical activation. Considering the activation reagent amount and modification temperature, the pore structure conducive to CO 2 adsorption was obtained. NOCK-400-1 exhibits maximum CO 2 capacity of 6.77 mmol g −1 at 0 °C and 4.46 mmol g −1 at 25 °C, 1 bar. It also presents high dynamic CO 2 adsorption capacity under 15% CO 2 /85% N 2 at ambient temperature and excellent adsorption regenerability. The results show that the improvement of CO 2 adsorption performance is mainly due to the synergistic effect of codoping nitrogen and oxygen. The codoping method effectively improves the relative contents of pyrrolic-N, pyridinic-N, and phenolic hydroxyl with promoting the synthesis of amorphous carbon. Furthermore, the codoping method enhances the porosity of NOCKs with less consumption of KOH. The density functional theory (DFT) calculations also demonstrate two kinds of van der Waals actions (namely, dispersion interaction and electrostatic attraction) for CO 2 adsorption on the nitrogen and oxygen codoped carbon surface. Additionally, the physical adsorption mechanism on the heterogeneous surface of adsorbents is confirmed by adsorption isotherm and thermodynamic study. Therefore, nitrogen and oxygen codoped porous carbons are a promising sorbent for CO 2 capture, which provides the effective information for carbon design.
The efficient separation of CO2 from air remains
an
important and challenging goal for direct air capture (DAC). Herein,
iron-containing 13X zeolite (Fe@13X) with an efficient separation
of CO2 from the air was synthesized via a simple one-step
in situ crystallization method. The results demonstrate that Fe@13X
exhibited outstanding DAC performance (the CO2 capacity
of Fe@13X was 0.64 mmol/g, much higher than the 13X zeolite under
simulated air), which was attributed to the introduction of Fe atoms,
effectively narrowing the 13X micropore channel. Moreover, the DAC
adsorption performance of Fe@13X in the temperature range from 25
to 75 °C was explored by combined thermogravimetric analysis
and differential scanning calorimetry. The results revealed that low
temperatures were more favorable for the adsorption of CO2 with a high adsorption rate but less selectivity. Furthermore, Fe@13X
showed a 3 times higher CO2 production (0.003 kgCO2/kgads·h) and 3.6 times lower desorption energy (0.005
kW h/kgCO2
) than 13X zeolite in 400 ppm CO2 in N2. Finally, Fe@13X exhibited excellent cycle
stability in simulated air and maintained its initial CO2 uptake in 10 consecutive cycles, showing the broad application prospects
of materials in industrial adsorption and separation.
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