Fabrication of Robust Covalent Organic Frameworks for Enhanced Visible-Light-Driven H₂ Evolution

Abstract

Developing photocatalysts capable of visible-lightdriven water splitting to produce clean hydrogen (H 2 ) is one of the premier challenges for solar energy conversion into clean and sustainable fuels. Inspired from the structure feature of photosystem I in nature, we have designed and synthesized a series of robust covalent organic frameworks (NKCOFs = Nankai University COFs) based on electric donor−acceptor moieties, in which the electron-donor group of pyrene can be used for harvesting light. Meanwhile, benzothiadiazole with different functional groups was introduced as an electron acceptor to tune the light-adsorption ability of COFs. Notably, the activity of NKCOF-108 for photochemical H 2 evolution under visible light was among the highest in COFs without hybridization with other materials. We attribute the high hydrogen evolution rate of NKCOF-108 to its distinct structural features and wide visible-lightresponse range. The highly ordered layered structure ensures that sufficient active sites are accessible for H 2 production, and the donor−acceptor design can promote the separation of photogenerated carriers. Our findings have provided an effective strategy to design photocatalysts for light-driven H 2 evolution.

Enormous Promotion of Photocatalytic Activity through the Use of Near-Single Layer Covalent Organic Frameworks

“…However, most of COFs show mediocre activity in photocatalytic H 2 evolution (PHE) compared with traditional inorganic semiconductors, which is mainly related to the difficulty in dissociation of excitons and the rapid recombination of photogenerated electrons and holes during photocatalytic process. 19 Several strategies have been developed to improve the charge separation efficiency of COFs, for example incorporating donor-acceptor (D-A) moieties 20,21 or halogen atoms in COFs, 22,23 constructing novel πconjugated building blocks, 24 and generating junctions with other semiconductors. 25 In addition to the above strategies, reducing the particle size of COFs to nanometer scale is a more facile method to improve the charge separation efficiency due to the possibility of charge carrier recombination is reduced in the short diffusion distance 26 .…”

Covalent organic frameworks with high quantum efficiency in photocatalytic hydrogen evolution: mediating charge separation

“…3d, Supplementary Table 5 and 6). [32][33][34][35][36][37][38][39][54][55][56][57][58][59][60][61][62][63][64][65][66] As compared with the reported COF/polymer-based photocatalyst, CN-CON showed the highest AQE as far as we know, which was in a comparable level to that of previously reported star inorganic Pt-PdS/CdS photocatalyst. [4] Even comparing with the H 2 evolution rate normalized by the mass, CN-CON is suprior to most of the COFs/polymer-based photocatalyst.…”

Structure evolution of thiophene-containing conjugated polymer photocatalysts for high-efficiency photocatalytic hydrogen production

“…S9). Although the photocatalytic stability of PyTP-2 is less than that of the state-of-art polymer photocatalysts [50][51][52], the HER of 17.5 mmol h −1 g −1 of PyTP-2 after 24 h photocatalytic reaction is still much higher than that of most reported polymer photocatalysts [53][54][55]. The structure characterizations of the recovered sample of PyTP-2 after 24 h photocatalytic reaction demonstrate that no any obvious change in the chemical structure could be observed, as evidenced by the results of FT-IR and solid state 13 C NMR (Fig.…”