Noble Gas Separation using PG-ESX (X = 1, 2, 3) Nanoporous Two-Dimensional Polymers

Abstract

Using planewave pseudopotential density functional theory and classical molecular dynamics simulations, we investigate the transport of noble gases through a family of two-dimensional hydrocarbon polymer membranes that generalize the “porous graphene” (PG) material synthesized by Bieri et al. by insertion of (E)-stilbene (ES) groups. We find that density functional theory overestimates the barrier height and empirical dispersion corrections underestimate the barrier height, compared to reference MP2/cc-pVTZ calculations on PG. The barrier height for noble gas transport is greatly reduced from PG to PG-ES1, but additional increases in the size of the pore in PG-ES2 and PG-ES3 lead to an attractive potential well instead of a repulsive barrier. Using the computed potential energy surfaces, we compute pressure- and temperature-driven tunneling probabilities of He isotopes, and refit an improved classical force-field. Using classical molecular dynamics simulations, we find that PG-ES1 has an He permeance of 6 × 106 GPU, which is 90 times greater than that of PG, and demonstrate high selectivity for He versus CH4, Ar, and CO2. These results indicate that PG-ES1 is a promising membrane material for separating He from natural gas, and separating He isotopes by tunneling differences.

Graphdiyne Pores: “Ad Hoc” Openings for Helium Separation Applications

“…S1) even if we do not consider that this effect can alter significantly the very favourable He/CH 4 and Ne/CH 4 probability ratios we have found. Further effects due to the neglect of both the interaction and competition of single components in the gas mixtures are not expected to provide significant deviations 13 in the obtained S behavior at least around and above room temperature.…”

“…The successful synthesis of these materials has led to important theoretical studies devoted, firstly, to their application as effective single-layer membranes for gas separation and water filtration technologies [7][8][9][10][11] and, secondly, to the tailoring of related porous 2D structures by changing pore shape and size through the incorporation of functional groups. [12][13][14][15] In this work we want to assess the capability of the recently synthesized graphdiyne and 2DPPH materials as efficient membranes for helium separation applications. As it is well known, helium is an irreplaceable natural resource and its growing demand in a variety of industrial and scientific applications, together with ongoing production deficiencies, has recently led to shortages of this element.…”

“…18 In principle membrane-based gas separation has a much lower thermodynamic cost 19 and recent theoretical works have proposed the use of 2D membranes for the chemical 7,8,13,20 and isotopic 8,12,21,22 separation of He gas. In particular, studies on He permeability through 2DPPH membranes were already addressed 7,8 but, to our knowledge, the graphdiyne capability for He separation has not been investigated yet.…”

Efficient helium separation of graphitic carbon nitride membrane

“…Here, we assumed a classical Boltzmann distribution for the velocities of both 3 He and 4 He as suggested by previous studies [19,20,22,43,44]. This strategy not only provides a more conservative estimation of 3 He/ 4 He selectivity, but also avoids the complexity of dealing with a mixed nonideal quantum gas composed of fermionic 3 Although the g-C 3 N 4 membrane exhibits great selectivity of 3 He at low temperature, the transmission probability is 10 -34 at 49 K (Fig.…”

Environmental applications using graphene composites: water remediation and gas adsorption

“…An interesting theoretical study by Brockway and Schrier has shown that a graphene membrane model based on a previously synthesized graphene porous membrane can be used to separate He from natural gas. 226,227 The authors conclude that the porous graphene (E)-stilbene 1 material outperforms existing materials in terms of selectivity and permeance.…”