Gas Permeation and Separation Characteristics of Microporous TpHz COF Membranes Synthesized by Substrate-Assisted Interfacial Polymerization

Jose Edgardo Lopez-Cazares, Kyungtae Kim, Jerry Y.S. Lin, Kailong Jin

Research output: Contribution to journalArticlepeer-review

Abstract

Microporous two-dimensional covalent organic framework (2D COF) membranes offer promise for gas separation applications, but their gas transport mechanism remains unclear. In this study, a TpHz 2D COF membrane supported on a macroporous nylon substrate is prepared by substrate-assisted interfacial polymerization under mild conditions. The formation of a continuous and dense thin (∼300 nm thick) TpHz layer is confirmed by scanning electron microscopy and Fourier transform infrared spectroscopy. Characterization by X-ray diffraction, grazing incidence wide-angle X-ray scattering, and N2 porosimetry qualitatively reveals the microstructures of the supported TpHz membranes, i.e., they comprise partially oriented 2D COF lamellar crystallites with moderate crystallinity in an eclipsed (AA) stacking geometry, centering the effective membrane pore size distribution at ∼1.1 nm. Single gas permeation data show that the transport of common molecular gases, including H2, He, CH4, N2, and CO2, through the synthesized TpHz membranes follows the Knudsen transport mechanism, where single gas permeance decreases with an increasing molecular weight and permeation temperature. Binary gas separation results show that in the equimolar CO2/N2 mixture, the presence of the CO2 surface flow slightly hinders the N2 flow at room temperature due to the reduced membrane channel size by the adsorbed CO2 gas layer on TpHz’s pore wall. In contrast, permeation of the equimolar CH4/N2 binary mixture does not exhibit a discernible surface flow of both gases due to their much lower gas uptake on TpHz, and their transport mechanism follows Knudsen-like behavior.

Original languageEnglish (US)
Pages (from-to)3684-3694
Number of pages11
JournalIndustrial and Engineering Chemistry Research
Volume63
Issue number8
DOIs
StatePublished - Feb 28 2024

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • Industrial and Manufacturing Engineering

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