Mohammad Tohidivahdat^1,2*, Davide Campi^2*, Nicola Colonna^2,3*, Luis Francisco Villalobos^1*, Nicola Marzari^2*, Kumar Agrawal Varoon^1*

1 Laboratory of Advanced Separations (LAS), École Polytechnique Fédérale de Lausanne (EPFL), Switzerland

2 Theory and Simulation of Materials (THEOS) and National Centre for Computational Design and Discovery of Novel Materials (MARVEL), EPFL, Lausanne, Switzerland

3 Laboratory for Neutron Scattering and Imaging (LSN), Paul Scherrer Institute, 5232 Villigen PSI, Switzerland

* Corresponding authors emails: mohammad.vahdat@epfl.ch, davide.campi@epfl.ch, nicola.colonna@psi.ch, francisco.villalobos@epfl.ch, nicola.marzari@epfl.ch, kumar.agrawal@epfl.ch

DOI10.24435/materialscloud:vp-ms [version v1]

Publication date: Feb 07, 2021

How to cite this record

Mohammad Tohidivahdat, Davide Campi, Nicola Colonna, Luis Francisco Villalobos, Nicola Marzari, Kumar Agrawal Varoon, Efficient Kr/Xe separation from triangular g-C3N4 nanopores: density-functional theory calculations benchmarked with random phase approximation, Materials Cloud Archive 2021.30 (2021), https://doi.org/10.24435/materialscloud:vp-ms

Description

Poly(triazine imide) or PTI is a promising material for molecular sieving membranes, thanks to its atom-thick ordered lattice with an extremely high density (1.6 × 10^14 pores/cm2) of triangular-shaped nanopores of ~0.34 nm diameter. Here, we investigate the application of PTI nanopores in the purification of Kr from Xe to reduce the storage volume of the mixture of 85Kr/Xe. Using van-der-Waals density-functional theory (vdW-DFT) calculations, benchmarked against the random phase approximation (RPA), we calculate the potential energy profiles for Kr and Xe across the nanopores. For each gas, starting from the RPA potential-energy profile, the force-field parameters to be used in the classical molecular dynamics framework are trained to calculate the Helmholtz free energy barrier as a function of temperature, and therefore, the corresponding entropic loss. Overall, due to the much higher activation energy from the adsorbed state in Xe (17.61 and 42.10 kJ/mole for Kr and Xe, respectively), a large Kr/Xe separation selectivity is postulated from the PTI membrane. Furthermore, the combination of atom-thick PTI lattice and high pore density leads to extremely large yet selective permeances for Kr. For example, Kr permeance of 1000 gas permeation units (GPU) accompanying a large Kr/Xe selectivity (>10000) is calculated at 25 °C, significantly better than the state-of-the-art membranes for Kr/Xe separation, making PTI-based membranes a leading candidate to process the hazardous waste of 85Kr/Xe mixture.

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File name	Size	Description
README.txt MD5md5:6320b4df670c86d6370c1c29080ad749	2.1 KiB	It explains what is inside the folder
Calculations.zip MD5md5:a4eee83dbe3c8c16efddd3232a590a30	25.2 MiB	Contains all the DFT and RPA calculations

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Keywords

carbon nitrides nanoscale transport density-functional theory random phase approximation van-der-Waals approximations MARVEL EPFL SNSF CSCS