The Linkage‐Moderated Covalent Organic Frameworks with C=N and NN on Charge Transfer Kinetics Towards the Robust Photocatalytic Hydrogen Activity

Abstract

Since the linkages structured in covalent organic frameworks (COFs) usually impact the charge transfer behavior during photocatalytic hydrogen evolution reaction (pc‐HER), linkage dependence on charge transfer kinetics should be further claimed. Herein, COFs with N‐based linkages and pyrene‐based building nodes are constructed to enable us to obtain new clues about the charge transfer behavior and evolution tendency relevant to linkages at a molecular level for pc‐HER. It is demonstrated that photo‐excited electrons preferably move to the N sites in ‐C=N‐ linkage for pc‐HER and are trapped around ‐N=N‐ linkage as well. A high electron transfer rate does not point to high photocatalytic activity directly, while a small difference between the electron transfer rate and electron recombination rate ΔkCT − CR predicts the inefficiency of charge transfer in Azo‐COFs. Contrarily, large value of ΔkCT − CR in the case of Py‐COFs, demonstrats an unimpeded charge transfer process to result in boosted pc‐HER rate (2027.3 µmol h−1 g−1). This work offers a prominent strategy for the reasonable design of efficient photocatalysts at the molecular level for structural regulation and achieves an efficient charge transfer process for the pc‐HER process.

Construction and Electrochromic Properties of Two-Dimensional Covalent Organic Frameworks with Donor-Acceptor Structures of Triphenylamine and Bipyridine

“…3b), the characteristic peak of the stretching vibration of the C=N bond appeared at 1584 cm −1 , and the characteristic peaks of the N-H and C=O bonds disappeared completely, which was consistent with the analysis results of the infrared spectra. The intensity of the characteristic C=N bond peaks 42 increased with the extension of the reaction time, which indicated that the backbone structure of COF TPDA-BPDA had been gradually perfected, and also confirmed the successful construction of COF TPDA-BPDA based on the Schiff base reaction.…”

Inducing local charge polarization by constructing isomeric covalent organic frameworks with different orientations of imine bonds for enhancing photocatalytic hydrogen evolution

“…Recent years have seen several published studies focusing on the chemical bond connections in COFs. 25–27 Investigating performance changes induced by different connection modes contributes to a better understanding of the reaction mechanisms involved in COF photocatalytic processes. For instance, Han et al found that imine- and vinylene-linked COFs show different charge-transfer pathways, affecting exciton relaxation.…”