(248d) High Density of Pyridinic Nitrogen Substituted Atom-Thick Pores on Single-Layer Graphene for Rapid and Selective CO2 transport

Single-layer graphene, hosting a high density of heteroatoms-substituted atom-thick pores, has the potential to achieve high-performance membrane-based molecular separation [1]. The heteroatoms-substituted pores offer the shortest transport pathway across the membrane as well as competitive sorption-based selectivity for the target molecules. For gas separation applications, especially carbon capture, this requires the incorporation of a high-density of Å-scale pores with doping of electronegative atoms such as N. In this presentation, I will discuss our approach where we successfully incorporated a high density of pyridinic-N-substituted pores in graphene, and achieved a high-performance CO₂/N₂separation.

We developed a model which predicts the oxidation of graphene with ozone [2]. The output of the model is pore size distribution (PSD) in terms of the number of missing carbon atoms. Based on screening reaction parameters with the model, we developed an oxidation protocol to achieve a narrow PSD for Å-scale pores with a high pore density (up to 10¹³ cm^-2, Figure 1A). Essentially, the reaction temperature, time, and ozone concentration were controlled to control nucleation and pore expansion rates.

Next, I will discuss substituting N atoms on the graphene nanopores for carbon capture [3]. Briefly, the pyridinic-N-substituted pore is achieved by a facile reaction of O₃-etched with NH₃. The pyridinic-N-substituted pores show a rapid and quantitatively reversible complexation of CO₂ with pyridinic N by cycles of adsorption and desorption in the spectroscopy (Figure 1B). The phenomenon is also visualized by microscopy where pores are observed occupied and empty upon adsorption and desorption, respectively. The strong competitive sorption on CO₂ leads to an attractive carbon capture performance (Figure 1C), even in the dilute CO₂ source. Thanks to the high density of CO₂-philic and N-substituted 2D pores, it led to a large CO₂/N₂ separation factor and high CO₂ permeance (Figure 1D). Overall our approach makes the prospect of porous graphene-based membranes highly attractive for gas separation.

References

[1] L. Wang, M.S.H. Boutilier, P.R. Kidambi, D. Jang, N.G. Hadjiconstantinou, R. Karnik, Fundamental transport mechanisms, fabrication and potential applications of nanoporous atomically thin membranes, Nat. Nanotechnol. 12 (2017) 509–522. https://doi.org/10.1038/nnano.2017.72.

[2] K.-J. Hsu, L.F. Villalobos, S. Huang, H.-Y. Chi, M. Dakhchoune, W.-C. Lee, G. He, M. Mensi, K.V. Agrawal, Multipulsed Millisecond Ozone Gasification for Predictable Tuning of Nucleation and Nucleation-Decoupled Nanopore Expansion in Graphene for Carbon Capture, ACS Nano. 15 (2021) 13230–13239. https://doi.org/10.1021/acsnano.1c02927.

[3] K.-J. Hsu, S. Li, M. Micari, H.-Y. Chi, L. Zhong, L. F. Villalobos, S. Huang, X. Duan, A. Züttel, K.V. Agrawal, Pyridinic nitrogen substituted two-dimensional pores for rapid and selective CO2 transport, Nature Energy, under review.