本文要点：
利用半导体光催化剂对过氧化氢（H2O2）进行人工光合作用是一种环保、节能的方法，正受到人们的关注。共价有机框架（COFs）由于其可调节的结构和功能多样性，在光催化生产H2O2方面表现出很大的前景。而生成H2O2的效率与COFs的光电性质及其活性位点的微环境密切相关。
本文报道了合成具有给受体（D-A）基团的吡啶基亚胺功能化COFs（PyIm-COFs）以提高H2O2的生产效率。通过采用不同氟取代的苯并噻唑（BT）单元，优化了活性位点的电子环境，优化了选择性双电子（2e−）氧还原反应（ORR）。
在合成的COFs中，PyIm-BT_F具有最高的光催化活性，H2O2产率达到5342 µmol g−1 h−1。本文强调了D-A基团在合理设计COF基光催化剂中的重要性，通过优化活性位点环境为可持续生产H2O2提供了一种新的策略。
Figure 2. a–d) PXRD patterns, e–h) nitrogen adsorption and desorption isotherms (insets: pore size distributions), and i–l) HR-TEM images of PyIm-B, PyIm-BT_H, PyIm-BT_F, and PyIm-BT_2F.
Figure 4. a) Time-dependent H2O2 using visible light for PyIm-COFs (10 mg catalyst, 𝜆 > 420 nm 300 W Xe lamp). b) AQY of PyIm-BT_F at selected wavelengths (420, 500, 520, 550, and 600 nm). c) Long-term photocatalytic H2O2 production of all PyIm-COFs. d) H2O2 production under different conditions (dark, Ar, Air, and O2). e) The Koutechy–Levich plots. f) H2O2 production of PyIm-COFs with different scavengers over one hour of PyIm-COFs.
Figure 5. a) Transient photocurrent, b) EIS Nyquist plots of PyIm-COFs. c) EPR CB electron spectra of PyIm-BT_F during and after visible light irradiation (>420 nm, 300 W Xe lamp). d) Integrated PL emission intensity as a function of temperature from 75 to 250 K for PyIm-BT_F.
Figure 7. a) EPR spectra of PyIm-COFs with DMPO as an electron-trapping agent. b) In situ DRIFTS spectra for H2O2 production of PyIm-BT_F. c) The O2 adsorption model in site 2 of PyIm-BT_H, PyIm-BT_F, and PyIm-BT_2F. d) The adsorption free energy of O2 on optimum sites. e) Free energy diagrams for the reduction of O2 to H2O2 in site 2. f) Different charge densities for O2 adsorption in site 2 of PyIm-B, PyIm-BT_H, PyIm-BT_F, and PyIm-BT_2F.
https://doi.org/10.1002/aenm.202500341
