Organic Conjugated Trimers with Donor–Acceptor–Donor Structures for Photocatalytic Hydrogen Generation Application

Abstract

Organic donor-acceptor-donor (D-A-D) polymers or small molecules are widely investigated in organic solar cells (OSC) due to their broad light absorption, narrow band gap, excellent charge mobility and exciton seperation at the interface. However, studies of conjugated small molecules with D-A-D molecule structures as photocatalytically active materials are still rare. In this work, we give an unprecedented demonstration that photocatalytic activity can in fact be affected by tuning the D and A.Especially, the EBE trimer, comprising 3,4-ethylenedioxythiophene (E) and benzothiadiazole (B) units, exhibits the best photophysical, chemical and photocatalytic properties compared to other D-A-D combinations of D and A. Detailed kinetic studies show that all these trimers in organic solution present relatively long-lived and highly emissive photogenerated singlet excitons (τ = 4 -13 ns; φem = 0.5 -0.9) as judged by photoluminescence and transient absorption measurements, while in specific cases formation of long-lived triplet states can be identified. Organic microparticles of the trimers are efficiently formed in aqueous solution by nanoprecipitation, and rapid photoinduced electron release/injection to the solvent is evidenced spectroscopically. The results indicate that organic small molecule structures with D-A-D structures pave a new pathway for photocatalytic solar-to-chemical energy conversion of novel small organic molecules.

Organic Donor‐Acceptor Systems for Photocatalysis

“…Eric Cloutet et al also constructed a D‐A‐D conjugated molecule using carbazole (C) as the D unit and quinoxaline (Q) and benzothiadiazole (B) as the A unit. [ 59 ] As in Figure 3c , the CBC and CQC trimers show stable photocatalytic hydrogen evolution performance.…”

“…As in Figure 2b , quinoxaline (Q) and benzothiadiazole (B) are chosen as A units, and 3,4‐ethylenedioxythiophene (E) and thiophene (T), both with strong electron‐donating ability, are used as D units, respectively. [ 59 ] The D‐A‐D molecule (EBE) comprising E and B units performs the best photochemical performance with the photocatalytic hydrogen evolution rate of 142 µmol g −1 h −1 . Naphthalene diimide (NDI) is a classical n‐type semiconductor with superior electron‐withdrawal and charge transport properties.…”

Self-assembled π-conjugated chromophores: preparation of one- and two-dimensional nanostructures and their use in photocatalysis

“…4a). 48,49 In the presence of the triethanolamine (TEOA) sacrificial donor, the rod-like aggregates photoproduced H 2 with an AQY of approximately 2% (400-450 nm), which was attributed to a combination of broad visible light absorption, a small band gap, wettability, and long exciton lifetimes. Furthermore, it was observed that no additional co-catalyst was added, and the residual palladium from cross-coupling was found to impact the photocatalytic activity.…”

Introduction of electron-deficient unit in resorcinol-formaldehyde resin to construct donor–acceptor conjugated polymer for enhancing photocatalytic H2O2 production

“…11,17 Signicantly, recent studies have suggested that the construction of intramolecular donor-acceptor (D-A) conjugated polymers by embedding donor/acceptor groups may be a potential method for improving photocatalytic performance. [18][19][20] In general, the potential difference between donor and acceptor groups can effectively improve the separation of photoinduced charges. 21,22 Although D-A conjugated polymers are promising semiconductors for photocatalytic applications, construction methods are usually too complex, and the mechanisms of action are not satisfactorily revealed.…”