CO₂ Adsorption by Amino-Functionalized Graphene-Silica Gels

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Ordered mesostructures, including mesoporous silica and organic/inorganic nanocomposites, are synthesized using surfactants to control molecular organization.
• Graphene derivatives offer unique properties for creating novel nanocomposites with enhanced functionalities when intercalated within mesostructures.
• Amine functionalization is a key strategy for enhancing the CO2 adsorption capabilities of porous materials.

Purpose of the Study:

• To evaluate the CO2-adsorption relevance and cycling stability of amine-functionalized graphene oxide-silica (GO-SiO2) and reduced graphene oxide-silica (rGO-SiO2) gels.
• To investigate the structural and textural properties of these graphene-silica nanocomposites.
• To establish the potential of these materials as effective CO2 capture adsorbents.

Main Methods:

• Synthesis of GO-SiO2 and rGO-SiO2 gels with controlled mesoporous silica domains between graphene layers.
• Characterization using X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TG), mass spectrometry (MS), N2 adsorption-desorption isotherms, and transmission electron microscopy (TEM).
• Evaluation of CO2 adsorption capacity and cycling stability after amine functionalization (APTMS).

Main Results:

• The synthesized materials exhibited a laminar architecture with specific surface areas of 446 m2·g-1 for GO-SiO2 and 710 m2·g-1 for rGO-SiO2.
• Amine-functionalized rGO-SiO2-APTMS demonstrated high CO2-adsorption capacity and excellent cycling stability, retaining approximately 96.3% of its initial uptake after 50 cycles.
• GO-SiO2-APTMS also showed good stability, retaining around 90.0% of its initial uptake after 50 cycles.

Conclusions:

• Amine-grafted graphene-silica gels, particularly rGO-SiO2-APTMS, are promising adsorbents for CO2 capture due to their high surface area, hierarchical porosity, and functionalization amenability.
• The laminar architecture and mesoporous silica domains contribute to the enhanced adsorption properties.
• The materials exhibit robust cycling stability, crucial for practical CO2 capture applications.