Three-Component Donor−π–Acceptor Covalent–Organic Frameworks for Boosting Photocatalytic Hydrogen Evolution

Abstract

Two-dimensional covalent−organic frameworks (2D COFs) have recently emerged as great prospects for their applications as new photocatalytic platforms in solarto-hydrogen conversion; nevertheless, their inefficient solar energy capture and fast charge recombination hinder the improvement of photocatalytic hydrogen production performance. Herein, two photoactive three-component donor−π−acceptor (TCDA) materials were constructed using a multicomponent synthesis strategy by introducing electrondeficient triazine and electron-rich benzotrithiophene moieties into frameworks through sp 2 carbon and imine linkages, respectively. Compared with two-component COFs, the novel TCDA-COFs are more convenient in regulating the inherent photophysical properties, thereby realizing outstanding photocatalytic activity for hydrogen evolution from water. Remarkably, the first sp 2 carbon-linked TCDA-COF displays an impressive hydrogen evolution rate of 70.8 ± 1.9 mmol g −1 h −1 with excellent reusability in the presence of 1 wt % Pt under visible-light illumination (420−780 nm). Utilizing the combination of diversified spectroscopy and theoretical prediction, we show that the full π-conjugated linkage not only effectively broadens the visible-light harvesting of COFs but also enhances charge transfer and separation efficiency.

Strategic design of covalent organic frameworks (COFs) for photocatalytic hydrogen generation

“…In this regard, Liu and co-workers have demonstrated the structural advantages of three-component donor-p-acceptor (TCDA) COFs, where three-component COFs have shown higher activity compared to analogous twocomponent COFs consisting of a node and linker, respectively. 115 Following the multi-component strategy for the 13a). A sp 2 -carbon-linked COF-JLU35 (l = 616 nm, s = 2.68 ns) exhibited a red-shied absorption spectrum and longer excited state lifetime compared to COF-JLU36 (l = 548 nm, s = 0.73 ns), indicating enhanced p-electron efficiency and improved charge separation in the fully conjugated sp 2 -carbon bond (Fig.…”

“…In this regard, Liu and co-workers have demonstrated the structural advantages of three-component donor–π–acceptor (TCDA) COFs, where three-component COFs have shown higher activity compared to analogous two-component COFs consisting of a node and linker, respectively. 115 Following the multi-component strategy for the synthesis of two isomorphic TCDA COFs, the sp 2 -carbon-linked COF-JLU35 was synthesised by Knoevenagel condensation between electron-rich benzo[1,2- b :3,4- b ′:5,6- b ′′]trithiophene-2,5,8-tricarbaldehyde (BTT), electron-poor 1,3,5-tris-(4-formyl-phenyl)triazine (TFPT) and 1,4-phenyldiacetonitrile (PDAN) in the presence of a catalytic amount of Cs 2 CO 3 . On the other hand, imine-linked COF-JLU36 was prepared by Schiff base condensation of benzo[1,2- b :3,4- b ′:5,6- b ′′]trithiophene-2,5,8-tricarbaldehyde (BTT), 1,3,5-tris-(4-formylphenyl)triazine (TFPT) and 1,4-phenylenediamine (PDA) in the presence of acetic acid catalyst (Fig.…”

Impact of the Crystallinity of Covalent Organic Frameworks on Photocatalytic Hydrogen Evolution

“…Therefore, the rational design of donor− acceptor structures offered an interesting possibility to improve the photocatalytic hydrogen generation efficiency of COFs. 120,121 4. Catalyst: The catalyst also plays an important role in forming the crystalline structure of COFs.…”

Metal-free 3D donor–acceptor COF with low exciton binding for solar fuel production based on CO2reduction

“…In addition, the presence of donor-acceptor (D-A) moiety in an extended polymer network will facilitate efficient charge separation by lowering the exciton binding energy (E b ), resulting in efficient catalysis. 58,59 Within this frame of reference, we have constructed a donor-acceptor three-dimensional (3D) framework, TT-COF, based on tris(4-aminophenyl)amine (TAPA) and aldehyde derivative of tetra phenylethylene (TFTPE(CHO) 4 ). Between these two building blocks, TAPA is relatively more electron-rich and acts as a donor moiety, possessing excellent hole-conducting prociency.…”