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The influence of the amine structure (secondary, tertiary, pyridinic) in amine-functionalized polymeric membranes on the mechanism of CO2 transport across the membrane is investigated in this work using operando surface enhanced Raman spectroscopy (SERS) and in-situ transmission FTIR spectroscopy. Specifically, the mechanism of CO2 transport across poly-N-methyl-N-vinylamine (PMVAm), poly-N, N-dimethyl-N-vinylamine (PDVAm), and poly(4-vinylpyridine) (P4VP) membranes was investigated by measuring CO2 permeances/selectivities of the membranes and simultaneously detecting CO2 transport intermediates (e.g., carbamate, bicarbonate) formed in the membrane under operating conditions using SERS and FTIR spectroscopy. While permeation measurements suggest that CO2 moves across all membranes via a facilitated transport mechanism, operando SERS and in-situ FTIR results suggest that the molecular-level details of the facilitated transport process are highly sensitive to the structure of the amine functional group. For membranes with secondary (PMVAm) and tertiary (PDVAm) amines, CO2 moves across the membrane as a mixture of both carbamate and bicarbonate species. For P4VP, which has pyridinic amine groups, no CO2-derived intermediates were detected suggesting a new facilitated transport mechanism involving weak interactions between CO2 and the pyridinic nitrogen group without transformation of CO2 into carbamate, bicarbonate, or other intermediate species. Such a facilitated transport mechanism has not been reported in the literature to our knowledge.
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Multi-Functional Polymer Membranes Enable Integrated CO 2 Capture and Conversion in a Single, Continuous-Flow Membrane Reactor under Mild Conditions
Herein, we present a membrane-based system designed to capture CO2 from dilute mixtures and convert the captured CO2 into value-added products in a single, integrated process operated continuously at mild conditions. Specifically, we demonstrate that quaternized poly(4-vinylpyridine) (P4VP) membranes are selective CO2 separation membranes that are also catalytically active for cyclic carbonate synthesis from the cycloaddition of CO2 to epichlorohydrin. We further demonstrate that quaternized P4VP membranes can integrate CO2 capture, including from dilute mixtures down to 0.1 kPa CO2, with CO2 conversion to cyclic carbonates at 57 °C and atmospheric pressure. The catalytic membrane acts as both the CO2 capture and conversion medium, providing an energy-efficient alternative to sorbent-based capture, compression, transport, and storage. The membrane is also potentially tunable for CO2 conversion to a variety of products, including chemicals and fuels not limited to cyclic carbonates, which would be a transformative shift in carbon capture and utilization technology.
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- Award ID(s):
- 2144362
- PAR ID:
- 10499921
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- ACS Applied Materials & Interfaces
- Volume:
- 15
- Issue:
- 48
- ISSN:
- 1944-8244
- Page Range / eLocation ID:
- 56305 to 56313
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/acsami.3c13221
