TY - JOUR
T1 - Thin Composite Carbon Molecular Sieve Membranes from a Polymer of Intrinsic Microporosity Precursor
AU - Ogieglo, Wojciech
AU - Furchner, Andreas
AU - Ma, Xiaohua
AU - Hazazi, Khalid
AU - Alhazmi, Abdulrahman
AU - Pinnau, Ingo
N1 - KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): BAS/1/1323-01-01
Acknowledgements: This publication is based on work supported by the King Abdullah University of Science and Technology (KAUST). IP Baseline Funding (KAUST) BAS/1/1323-01-01 (WO, XM, KH, ATA, IP). Financial support by the Ministerium für Innovation,Wissenschaft und Forschung des Landes Nordrhein-Westfalen, the Regierende Bürgermeister von Berlin – Senatskanzlei Wissenschaft und Forschung, and the Bundesministerium für Bildung und Forschung, and the European Union through the EFRE program (ProFIT grant, contract no.: 10160255, 10160265, and 10160256) is gratefully acknowledged by AF. The authors gratefully acknowledge the possibility for an extensive use of the KAUST Solar Center infrastructure.
PY - 2019/5
Y1 - 2019/5
N2 - Ultra-thin composite carbon molecular sieve (CMS) membranes were fabricated on well-defined inorganic alumina substrates using a polymer of intrinsic microporosity (PIM) polyimide as precursor. Details of the pyrolysis-related structural development were elucidated using focused-beam, interference-enhanced spectroscopic ellipsometry (both in the UV-VIS and IR range) which allowed accurate determination of the film thickness, optical properties as well as following the chemical transformations. The pyrolysis-induced collapse of thin and bulk PIM-derived CMS membranes was compared with CMS made from a well-known non-PIM precursor 6FDA-DABA. Significant differences between the PIM and non-PIM precursors were discovered and explained by a much larger possible volume contraction in the PIM. In spite of the differences, surprisingly, the gas separation properties did not fundamentally differ. The high temperature collapse of the initially amorphous and isotropic precursor structure was accompanied by a significant molecular orientation within the formed turbostratic carbon network guided by the laterally constraining presence of the substrate. This manifested itself in the development of uniaxial optical anisotropy, which was shown to correlate with increases in gas separation selectivity for multiple technologically important gas pairs. Reduction of CMS skin thickness significantly below ~1 micron induced large losses in permeability coefficients with only small to moderate effects on selectivity. Remarkably, skin thickness reduction and physical aging seemed to superimpose onto the same trend, which explains and strengthens some of the earlier fundamental insights.
AB - Ultra-thin composite carbon molecular sieve (CMS) membranes were fabricated on well-defined inorganic alumina substrates using a polymer of intrinsic microporosity (PIM) polyimide as precursor. Details of the pyrolysis-related structural development were elucidated using focused-beam, interference-enhanced spectroscopic ellipsometry (both in the UV-VIS and IR range) which allowed accurate determination of the film thickness, optical properties as well as following the chemical transformations. The pyrolysis-induced collapse of thin and bulk PIM-derived CMS membranes was compared with CMS made from a well-known non-PIM precursor 6FDA-DABA. Significant differences between the PIM and non-PIM precursors were discovered and explained by a much larger possible volume contraction in the PIM. In spite of the differences, surprisingly, the gas separation properties did not fundamentally differ. The high temperature collapse of the initially amorphous and isotropic precursor structure was accompanied by a significant molecular orientation within the formed turbostratic carbon network guided by the laterally constraining presence of the substrate. This manifested itself in the development of uniaxial optical anisotropy, which was shown to correlate with increases in gas separation selectivity for multiple technologically important gas pairs. Reduction of CMS skin thickness significantly below ~1 micron induced large losses in permeability coefficients with only small to moderate effects on selectivity. Remarkably, skin thickness reduction and physical aging seemed to superimpose onto the same trend, which explains and strengthens some of the earlier fundamental insights.
UR - http://hdl.handle.net/10754/652850
UR - https://pubs.acs.org/doi/10.1021/acsami.9b04602
UR - http://www.scopus.com/inward/record.url?scp=85066115836&partnerID=8YFLogxK
U2 - 10.1021/acsami.9b04602
DO - 10.1021/acsami.9b04602
M3 - Article
C2 - 31042347
SN - 1944-8244
VL - 11
SP - 18770
EP - 18781
JO - ACS Applied Materials & Interfaces
JF - ACS Applied Materials & Interfaces
IS - 20
ER -