Side-Chain Modification in Conjugated Polymer Frameworks for the Electrocatalytic Oxygen Evolution Reaction

Abstract

Conjugated polymer frameworks (CPFs) have recently sparked tremendous research interest due to their broad potentials in various frontline application areas such as photocatalysis, sensing, gas storage, energy storage, etc. These framework materials, without sidechains or functional groups on their backbone, are generally insoluble in common organic solvents and less solution processable for further device applications. There are few reports on metal-free electrocatalysis, especially oxygen evolution reaction (OER) using CPF. Herein, we have developed two triazine-based donor–acceptor conjugated polymer frameworks by coupling a 3-substituted thiophene (donor) unit with a triazine ring (acceptor) through a phenyl ring spacer. Two different sidechains, alkyl and oligoethylene glycol, were rationally introduced into the 3-position of thiophene in the polymer framework to investigate the effect of side-chain functionality on the electrocatalytic property. Both the CPFs demonstrated superior electrocatalytic OER activity and long-term durability. The electrocatalytic performance of CPF2, which achieved a current density of 10 mA/cm2 at an overpotential (η) of 328 mV, is much superior to CPF1, which reached the same current density at an overpotential of 488 mV. The porous and interconnected nanostructure of the conjugated organic building blocks, which allowed for fast charge and mass transport processes, could be attributed to the higher electrocatalytic activity of both CPFs. However, the superior activity of CPF2 compared to CPF1 may be due to the presence of a more polar oxygen-containing ethylene glycol side chain, which enhances the surface hydrophilicity, promotes better ion/charge and mass transfer, and increases the accessibility of the active sites toward adsorption through lower π–π stacking compared to hexyl side chain present in CPF1. The DFT study also supports the plausible better performance toward OER for CPF2. This study confirms the promising potentiality of metal-free CPF electrocatalysts for OER and further sidechain modification to improve their electrocatalytic property.

Generation of covalent organic framework-derived porous N-doped carbon nanosheets for highly efficient electrocatalytic hydrogen evolution

“…S8 in ESI †. 51–53 The FE of TP-COF-C700 was calculated as 98%, which was very close to the ideal value of 100%.…”

Rationally Designed Cyclooctatetrathiophene‐Based Porous Aromatic Frameworks (COTh‐PAFs) for Efficient Photocatalytic Hydrogen Peroxide Production

“…The absorption peak of the C−N bond in PAF‐361 is around 1320 cm −1 [45] . Strong signals at 1511 and 1411 cm −1 demonstrate the successful inclusion of triazine rings in PAF‐363 [46] . The analysis of XPS measurements show that the C 1s of the three COTh‐PAFs have two major characteristic peaks located at 284.8 and 285.8 eV, which are assigned to the C=C and C−S bonds (Figure S3) [47,48] .…”

“…[45] Strong signals at 1511 and 1411 cm À 1 demonstrate the successful inclusion of triazine rings in PAF-363. [46] The analysis of XPS measurements show that the C 1s of the three COTh-PAFs have two major characteristic peaks located at 284.8 and 285.8 eV, which are assigned to the C=C and CÀ S bonds (Figure S3). [47,48] In addition, the peaks at 285.1 eV and 287.1 eV in the C 1s peaks can be attributed to CÀ N and C=N bonds.…”

In situ palladium-doped conjugated polymer network for visible light and natural sunlight-driven Suzuki type cross-coupling reaction at room temperature

“…2,7-Dibromofluorene and 2,7-dibromofluorenone were synthesized by following the methods from the previously reported literature 50,51 (ESI†). ((1,3,5-Triazine-2,4,6-triyl)tris(benzene-4,1-diyl))triboronic acid was also synthesized by following the previously reported method 52 (ESI†).…”