Advancing Molecular Sieving via Å-Scale Pore Tuning in Bottom-Up Graphene Synthesis

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Porous graphene films offer high-flux gas separation due to their atomic-scale thickness.
• Tunable pore size is crucial for selective gas separation, but challenging in scalable bottom-up synthesis.
• Existing methods for pore size tuning in graphene are typically post-synthetic and top-down.

Purpose of the Study:

• To develop a simple, scalable method for tuning pore size in bottom-up synthesized porous graphene.
• To investigate the effect of synthesis cooling rates on graphene nanostructure and pore size.
• To enhance the gas separation performance of porous graphene membranes.

Main Methods:

• Precipitation-based synthesis of porous graphene over catalytic nickel foil.
• Rapid cooling of the synthesis system (increased from -1 °C min^-1 to over -5 °C s^-1).
• Quantitative carbon-diffusion simulation, carbon concentration measurement, and graphene nanostructure imaging.

Main Results:

• Rapid cooling restricts carbon diffusion, increasing dissolved carbon availability for precipitation.
• Enhanced grain (inter)growth in graphene structures was observed.
• The H₂/CH₄ separation factor increased significantly from 6.2 to 53.3.

Conclusions:

• Increasing the cooling rate is an effective and simple strategy to tune pore size in bottom-up synthesized porous graphene.
• The developed method leads to significantly improved hydrogen/methane gas separation performance.
• This approach offers a scalable route for producing advanced porous graphene membranes for gas separation applications.