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Ionic Diode and Molecular Pump Phenomena Associated with Caffeic Acid Accumulated into an Intrinsically Microporous Polyamine (PIM‐EA‐TB)
Author(s) -
Li Zhongkai,
Wang Lina,
MalpassEvans Richard,
Carta Mariolino,
McKeown Neil B.,
Mathwig Klaus,
Fletcher Philip J.,
Marken Frank
Publication year - 2021
Publication title -
chemelectrochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.182
H-Index - 59
ISSN - 2196-0216
DOI - 10.1002/celc.202100432
Subject(s) - caffeic acid , microporous material , protonation , ionic bonding , chemistry , hydrogen bond , intercalation (chemistry) , molecule , inorganic chemistry , stereochemistry , organic chemistry , ion , antioxidant
The polymer of intrinsic microporosity PIM‐EA‐TB provides a molecularly rigid micropore structure containing tertiary amine sites and is shown here to interact with hydrogen bonding guest molecules such as caffeic acid. Voltammetric data with a PIM‐EA‐TB film on glassy carbon electrodes show that in both acidic solution (pH 2; PIM‐EA‐TB is protonated) and in neutral solution (pH 6; PIM‐EA‐TB is not protonated) caffeic acid is slowly accumulated into the microporous host. Binding constants are estimated and suggested to be linked to hydrogen bonding causing accumulation of caffeic acid. When employing PIM‐EA‐TB as an asymmetric membrane coated onto a 5 μm thick Teflon support film with 10 μm diameter microholes (using either a single microhole or a 10×10 array of microholes), binding of caffeic acid is shown to cause a modulation of the ionic current without affecting the pH‐dependent ionic diode behaviour. Two complementary types of effects of caffeic acid guests are discussed based on blocking anion diffusion pathways and based on removal of positive charges. The caffeic acid transport mechanism/efficiency is investigated in view of selective molecular pumping.