Authors

Abstract

We performed fixed-node diffusion Monte Carlo (DMC) calculations to investigate structural and energetic propertiesof graphenylene (GPNL), a two-dimensional network of sp2-bonded carbon atoms with large near-circular pores, andits H2 separation performance for gas mixtures. It is found that energetic stability of a GPNL monolayer is comparableto that of -graphyne, as evidenced by its large cohesive energy of 6.755(3) eV/atom. Diffusion barriers of severalgas molecules, including hydrogen, through a GPNL membrane, were determined from the analysis of their adsorptionenergies depending on the adsorption distance, which led to our estimation for hydrogen selectivity with respect to othertarget molecules. DMC hydrogen selectivity of a GPNL monolayer was found to be exceptionally high at 300 K, as highas 1010 to 1011 against CO and N2 gases. This, along with high hydrogen permeance due to its generic pore structure,leads us to conclude that GPNL is a promising membrane to be used as a high-performance hydrogen separator fromgas mixtures. We find that when compared to our DMC results, DFT calculations tend to overestimate H2 selectivity,which is understood to be mostly due to their inaccurate description of short-range repulsive interactions.