Tuning CO₂ Capture and Conversion with Metal-Organic Frameworks Crystallized in Aqueous Graphene Oxide Suspensions

Area of Science:

• Materials Science
• Green Chemistry
• Nanotechnology

Background:

• Traditional synthesis of metal-organic frameworks (MOFs) often involves harsh conditions, organic solvents, and high temperatures.
• Graphene oxide (GO) offers a unique platform for material synthesis due to its tunable properties and large surface area.
• Developing sustainable and efficient methods for MOF synthesis is crucial for environmental and industrial applications.

Purpose of the Study:

• To develop a green, solvent-free, and low-temperature procedure for synthesizing MOFs (Zn, Ni, Co) using graphene oxide aqueous suspensions.
• To investigate the influence of metal nature and graphene oxide characteristics on MOF properties and performance.
• To evaluate the CO2 adsorption capacity and catalytic activity of the synthesized MOFs in the cycloaddition of CO2 to epoxides.

Main Methods:

• Synthesis of MOFs (Zn, Ni, Co) in aqueous GO suspensions derived from graphitized or nongraphitized carbon nanofibers.
• Comprehensive material characterization using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), N2/CO2-physisorption, Raman, and X-ray photoelectron (XPS) spectroscopies.
• Assessment of CO2 adsorption and catalytic activity in the solvent-free cycloaddition of CO2 to epoxides.

Main Results:

• The nature of the metal and the defectivity of graphene oxide significantly influence MOF size, porosity, and defect density (noncoordinated linkers, open metal sites).
• The synthesized MOFs demonstrated substantially improved CO2 adsorption energy (up to 6 kJ·mol−1 increase) and uptake (up to 5 mmol·g−1 increase) compared to bulk MOFs.
• Enhanced catalytic activity (up to 35% rate increase) was observed for the MOFs in the CO2 cycloaddition reaction under ambient conditions.

Conclusions:

• A novel green synthesis route for MOFs on graphene oxide nanosheets was successfully established, avoiding organic solvents and high temperatures.
• The study highlights the critical role of metal choice and graphene oxide properties in tailoring MOF characteristics for superior CO2 capture and catalysis.
• These graphene oxide-supported MOFs represent promising materials for efficient and sustainable CO2 utilization and conversion.