Fig. 4. (a) Photocatalytic activities of Tf-TAPB-COF, Tf-TAPP-COF, Tf-TAPPM-COF, and Tf-TAPT-COF for H2O2 generation in deionized water without any sacrificial agents. (b) The control experiments of photocatalytic H2O2 production under different conditions (O2 and air). (c) Ultraviolet-visible diffuse reflection spectroscopy (UV/Vis DRS) spectrum and the apparent quantum yield (AQY) of Tf-TAPT-COF for H2O2 generation. (d) Amounts of H2O2 produced in tert-butanol (TBA, 10% v/v, as the ˙OH trapping agent), p-benzoquinone (PBQ, 5 mM, as the ˙O2− trapping agent), and AgNO3 (10 mM, as the electron trapping agent) by Tf-TAPB-COF, Tf-TAPP-COF, Tf-TAPPM-COF, and Tf-TAPT-COF. (e) Electron paramagnetic resonance (EPR) spectra (DMPO – ˙O2−) of Tf-TAPB-COF, Tf-TAPP-COF, Tf-TAPPM-COF, and Tf-TAPT-COF under dark and light irradiation. (f) In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) spectra versus illumination time for the photocatalytic system of Tf-TAPT-COF. The black dashed line represents the C N in Tf-TAPT-COF, while the green and blue dashed lines indicate the intermediates in the stepwise 1e− ORR pathway and the direct 2e− WOR pathway during photocatalysis, respectively.
