(397f) Pyridinic Nitrogen Substituted Two-Dimensional Pores for Rapid and Selective CO2 Transport from Graphene Membrane

2D films hosting tailor-made pores have the potential to achieve high-performance membrane-based molecular separation, and can mimic rapid and selective transport from the biological systems.[1] Porous single-layer graphene is an ideal 2D film for this purpose because the atom-thick pores in graphene minimize diffusional resistance for molecular transport.[2] While 2D pores in graphene are ideally suited for ambitious high-performance carbon capture, a longstanding challenge in achieving this arises from difficulties in tightly controlling the pore size distribution in a scalable manner. In this presentation, I will show a strategy for improving the tolerance with respect to pore size distribution by increasing the binding affinity of CO₂ with the pore.[3] This comprises of heteroatomic doping of the pore edge with pyridinic N to promote competitive CO₂ uptake via electrostatic interactions (Figure. 1).[4] Pyridinic N has been reported to complex with CO₂ driven by the Lewis acid-base interaction which involves a donation of electron charge from N (Lewis base) to CO₂.[5] N at the pore edge was placed by reducing oxidized graphene film by NH₃ where a spontaneous N-H dissociation has been predicted to promote N doping in the lattice. The incorporation of pyridinic N is confirmed by the emergence of N1s peak in the high-resolution X-ray photoelectron spectroscopy (XPS). Spontaneous but reversible uptake of atmospheric CO₂, in the form of complexed product, is observed. This is also corroborated by imaging pores using low-temperature scanning tunneling microscopy (LTSTM) where pores appear occupied and empty upon adsorption and desorption cycle, respectively. The high- affinity results in a high loading even from a dilute CO₂ feed which led to the realization of high CO₂ permeance (14190±1880 GPU) combined with a high CO₂/N₂ selectivity (43.7±7.5).

References

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2. Villalobos, L. F.; Babu, D. J.; Hsu, K.; Van Goethem, C.; Agrawal, K. V. Gas Separation Membranes with Atom-Thick Nanopores: The Potential of Nanoporous Single-Layer Graphene. Accounts Mater. Res. 3 (10), 1073–1087 (2022).
3. Hsu, K.; Li, S.; Micari, M.; Chi, H.; Zhong, L.; Francisco, L.; Huang, S.; Duan, X.; Züttel, A.; Agrawal, K. V. Pyridinic Nitrogen Substituted Two-Dimensional Pores for Rapid and Selective CO2 Transport. Submitted. Under review.
4. Luan, B. et al. Crown Nanopores in Graphene for CO2 Capture and Filtration. ACS Nano 16, 6274–6281 (2022).
5. Lim, G., Lee, K. B. & Ham, H. C. Effect of N-Containing Functional Groups on CO2 Adsorption of Carbonaceous Materials: A Density Functional Theory Approach. Phys. Chem. C 120, 8087–8095 (2016).