TY - JOUR
T1 - In-situ ATR-IR Spectroscopy Reveals Complex Absorption-Diffusion Dynamics in Model Polymer-Membrane-Catalyst Assemblies (PCMA)
AU - Enes da Silva, Maria Joao
AU - Lefferts, Leon
AU - Faria Albanese, Jimmy Alexander
N1 - Funding Information:
The microscopy works have been conducted in the “Laboratorio de Microscopias Avanzadas” at “Instituto de Nanociencia de Aragon – Universidad de Zaragoza”. Authors acknowledge the LMA-INA for offering access to their instruments and expertise, specially to R. Fernandez Pacheco and G. Antorrena. We are grateful to K. Altena-Schildkamp, T. Lubbers and Dr. Y. Yang for chemical analysis. We acknowledge B. Geerdink and Dr. J. Willott for technical support and for the input on the polymerization procedure, respectively. We are grateful to A. Mehendale, Dr. S. J. A. de Beer and Dr. I. Siretanu for the help in obtaining the AFM images. We thank J. Baptista and R. Postma for the initial help on the modelling input. We are grateful to Hugo Fernandes for the drawing of Figure 2a.
Publisher Copyright:
© 2022 The Authors. ChemCatChem published by Wiley-VCH GmbH.
PY - 2022/5/20
Y1 - 2022/5/20
N2 - Molecular transport in porous media plays an essential role in heterogeneous catalysis. Here, we have studied a Polymer-Membrane-Catalyst Assembly (PCMA) system consisting of PET membranes with a well-defined pore structure coated with thermo-responsive polymer (poly(n-isopropylacrylamide) or p-NIPAM) coupled to an in-situ ATR-IR cell containing palladium supported on γ-Al
2O
3. This PCMA model is designed to mimic the structure of a core-shell catalyst coated with stimulus responsive polymer. At low temperatures (<32 °C), where p-NIPAM is in its swollen state, the addition of polymer brushes caused a delay in CO chemisorption on Pd. Strikingly, when the polymer collapses (>32 °C), we observed faster CO−Pd saturation. Our multi-physics model of the CO transport and chemisorption on the PCMA suggests that the delay is caused by the strong affinity of the CO molecules with the polymer brushes. When stimulus responsive polymers are present, a complex interplay between diffusion and absorption determines the dynamic behavior of the system. Furthermore, we demonstrate that this behavior could be reversed by reducing the ratio of polymer inside the pores and the surface, in which the delay observed is now above the LCST. This new insights on the dynamics of transport, absorption, and chemisorption processes occurring on so-called “nano-reactors” provide new opportunities for developing new self-regulating catalysts with faster transitions between ON- and OFF- states.
AB - Molecular transport in porous media plays an essential role in heterogeneous catalysis. Here, we have studied a Polymer-Membrane-Catalyst Assembly (PCMA) system consisting of PET membranes with a well-defined pore structure coated with thermo-responsive polymer (poly(n-isopropylacrylamide) or p-NIPAM) coupled to an in-situ ATR-IR cell containing palladium supported on γ-Al
2O
3. This PCMA model is designed to mimic the structure of a core-shell catalyst coated with stimulus responsive polymer. At low temperatures (<32 °C), where p-NIPAM is in its swollen state, the addition of polymer brushes caused a delay in CO chemisorption on Pd. Strikingly, when the polymer collapses (>32 °C), we observed faster CO−Pd saturation. Our multi-physics model of the CO transport and chemisorption on the PCMA suggests that the delay is caused by the strong affinity of the CO molecules with the polymer brushes. When stimulus responsive polymers are present, a complex interplay between diffusion and absorption determines the dynamic behavior of the system. Furthermore, we demonstrate that this behavior could be reversed by reducing the ratio of polymer inside the pores and the surface, in which the delay observed is now above the LCST. This new insights on the dynamics of transport, absorption, and chemisorption processes occurring on so-called “nano-reactors” provide new opportunities for developing new self-regulating catalysts with faster transitions between ON- and OFF- states.
KW - UT-Hybrid-D
U2 - 10.1002/cctc.202101835
DO - 10.1002/cctc.202101835
M3 - Article
SN - 1867-3880
VL - 14
JO - ChemCatChem
JF - ChemCatChem
IS - 10
M1 - e202101835
ER -
