本文要点：
太阳能驱动氧还原反应(ORR)和水氧化反应(WOR)双通道产生H2O2是绿色和可持续的，但受到缓慢反应动力学的严重限制。构建具有有效活性中心的光催化剂是突破动力学瓶颈的捷径，具有重要意义。
在本文中，作者合成了两个新的中性菲啶基共价有机框架(PD-COF1和PD-COF2)用于光合成H2O2。与没有菲啶的对应物(AN-COF)相比，PD-COF1和PD-COF2的H2O2光合活性显著增强。
在不含牺牲剂的空气和纯水中，在氙灯和自然光下，PD-COF2的H2O2光生速率分别为6103和3646 μmol·g-1·h-1。
进一步的实验和理论研究表明，将菲啶单元引入到COFs中平稳地调节了电荷载流子动力学，并且在热力学上有利于分别在ORR和WOR路径中产生关键的OOH*和OH*中间体。
此外，这是中性菲啶部分第一次作为2e- WOR向H2O2光生成的光氧化单元。目前的工作揭示了探索新的催化中心的高性能H2O2合成。
Figure 1. Synthetic routes of PD-COF1, PD-COF2, and AN-COF.
Figure 2. Experimental, Pawley refined, and simulated PXRD patterns of (a) PD-COF1, (b) PD-COF2, and (c) AN-COF. (d) N2 sorption isotherms of PD-COF1, PD-COF2, and AN-COF; inserts were the pore size distribution curves.
Figure 3. (a) UV-vis DRS and Tauc plots of PD-COF1, PD-COF2, and AN-COF. (b) Mott-Schottky plot of PD-COF2. (c) Energy band structures of PD-COF1, PDCOF2, and AN-COF. (d) PL spectra of PD-COF1, PD-COF2, and AN-COF. (e) Time-resolved PL decay curves of PD-COF1, PD-COF2, and AN-COF (excited at 375 nm) with the instrument response function (IRF). (f) Transient photocurrent density of PD-COF1, PD-COF2, and AN-COF.
Figure 4. (a) Temporal H2O2 photoproduction curves over PD-COF1, PD-COF2, and AN-COF in air and pure water under visible light. (b) In air and pure water conditions, kf and kd during the photocatalytic H2O2 formation processes of PD-COF1, PD-COF2, and AN-COF. (c) H2O2 evolution rates at different atmospheres photocatalyzed by PD-COF1, PD-COF2, and AN-COF. (d) H2O2 generation rate over PD-COF1, PD-COF2, and AN-COF in the presence of scavengers for reactive oxygen species (β-carotene, 1 mM; TEMPOL, 1 mM) under illumination for 1 h in O2. (e) O2 •- generated EPR signals by PD-COF1, PD-COF2, and ANCOF trapped by DMPO (in the dark and light for 5 min). (f) O2 1 generated EPR signals by PD-COF2 trapped by TEMP with and without BQ (in the dark and light for 5 min). (g) H2O2 generation rate over PD-COF1, PD-COF2, and AN-COF in the presence of scavengers for electrons and holes (KBrO3, 1 mM; CH3CH2OH, 10%) under illumination for 1 h in Ar. (h) Electron transfer numbers and H2O2 selectivity of PD-COF2 in PBS (pH = 7) by RRDE. (i) DRIFTS spectra of PD-COF2 under darkness and illumination in O2.
Figure 5. (a) The photogenerated electron and hole distributions at the excited state of PD-COF1, PD-COF2, and AN-COF (brown areas indicate photogenerated electron-rich regions and blue areas indicate photogenerated hole-rich regions). (b) The optimal O2 adsorption sites on PD-COF1, PD-COF2, and AN-COF. (c) The optimal H2O adsorption sites on PD-COF1, PD-COF2, and AN-COF. (d) Gibbs free energy diagrams for the 2e- ORR reaction paths of PD-COF1, PD-COF2, and AN-COF on the sites in Figure 5b. (e) Gibbs free energy diagrams for the 2e- WOR reaction paths of PD-COF1, PD-COF2, and AN-COF on the sites in Figure 5c.
https://doi.org/10.1002/anie.202417115
