Surface Characteristics of Microporous and Mesoporous Carbons Functionalized with Pentafluorophenyl Groups

Abstract

The in situ diazonium reduction reaction is a reliable and well-known approach for the surface modification of carbon materials for use in a range of applications, including in energy conversion, as chromatography supports, in sensors, etc. Here, this approach was used for the first time with mesoporous colloid-imprinted carbons (CICs), materials that contain ordered monodisperse pores (10-100 nm in diameter) and are inherently highly hydrophilic, using a common microporous carbon (Vulcan carbon (VC)), which is relatively more hydrophobic, for a comparison. The ultimate goal of this work was to modify the CIC wettability without altering its nanostructure and also to lower its susceptibility to oxidation, as required in fuel cell and battery electrodes, by the attachment of pentafluorophenyl (-PhF) groups onto their surfaces. This was shown to be successful for the CIC, with the -PhF groups uniformly coating the inner pore walls at a surface coverage of ca. 90% and allowing full solution access to the mesopores, while the -PhF groups deposited only on the outer VC surface, likely blocking its micropores. Contact angle kinetics measurements showed enhanced hydrophobicity, as anticipated, for both the -PhF modified CIC and VC materials, even revealing superhydrophobicity at times for the CIC materials. In contrast, water vapor sorption and cyclic voltammetry suggested that the micropores remained hydrophilic, arising from the deposition of smaller N- and O-containing surface groups, caused by a side reaction during the in situ diazonium functionalization process.

Carbon black modified with 4‐hydroxymethylbenzenediazonium salt as filler for phenol‐formaldehyde resins and abrasive tools

“…During the modification, the pores are filled by the organic layer, which results in a reduction of their volume. The same relationship was found earlier for carbons modified by diazonium salts . This phenomenon is particularly evident in the case of micropores that did not occur after modification.…”

Influence of diazonium and surfactant modification of the mesoporous material on its adsorption properties

“…These groups are localized at the entrance of pores and then close or fill them (Toupin and Bélanger 2008). The same relationship was found earlier for carbons modified with diazonium salts (Li et al 2018;Geng et al 2012;Grondein and Bélanger 2011). The smallest change in both surface and volume was noted for the sample modified using 4-sulfobenzendiazonium salt.…”

Mechanically robust and thermally stable abrasive tools from phenolic resins reinforced with diazonium‐modified zeolites

“…The pore volume during modification decreases because they are filled by the organic layer. The same relationship was found for carbons modified by diazonium salts This dependence is particularly evident in the case of micropores which were not detected after modification. This is related to the presence of aryl groups which are localized at the entrance of micropores and close or fill them .…”