Insights into the CO Capture Characteristics within the Hierarchical Pores of Carbon Nanospheres Using Small-Angle Neutron Scattering.

Understanding adsorption processes at the molecular level has transformed the discovery of engineered materials for maximizing gas storage capacity and kinetics in adsorption-based carbon capture applications. In this work, we studied the molecular mechanism of gas (CO, H, methane, and ethane) adsorption inside an interconnected porous network of carbon. This was achieved by synthesizing novel macro-meso-microporous carbon (MC) nanospheres with interconnected pore structures. The MCs showed a CO capture capacity of 5.3 mmol/g at atmospheric CO pressure, with excellent kinetics. This was due to fast CO adsorption within the interconnected hierarchical macro-meso-microporous MC. In situ small-angle neutron scattering (SANS) under various CO pressures indicated that the macro- and mesopores of MC enable fast diffusion of CO molecules inside the micropores, where adsorbed CO molecules densify into a liquid-like state. This strong densification of CO molecules causes fast CO diffusion in the macro- and mesopores of MC, restarting the adsorption cycle for fresh CO molecules until all pores are completely filled. Notably, MC also showed good capture capacities for hydrogen and various hydrocarbons, with excellent selectivity toward ethane over methane.