本文要点：
共价有机框架(COFs)以分子结构的精确可调性而闻名，在光催化过氧化氢(H2O2)生产方面具有重要的前景。本文中，通过多组分反应系统地改变三嗪(TA)基COFs中的喹啉(QN)键，合成了六种具有相同骨架但不同取代基的R-QN-TA-COFs。
允许对COFs的光电特性和局部微环境进行微调，从而优化电荷分离并改善与溶解氧的相互作用。因此，MeO-QN-TA-COF被定制成在没有任何牺牲剂的水中的空气气氛下实现高达7384 µmol g⁻1 h⁻1的令人印象深刻的H2O2产生速率，超过了大多数报道的COF光催化剂。
通过五次连续回收实验和回收COF的表征，证明了其高稳定性。使用一系列猝灭实验、原位光谱分析和理论计算进一步研究了H2O2产生的反应机理。在MeO-QN-TA-COF上增强的光催化H2O2产生是通过2e⁻氧还原反应和水氧化反应途径。总的来说，连接微环境调节在太阳能驱动的有效光催化H2O2生产的COFs设计中的关键作用。
Scheme 1. Schematic illustration of R-QN-TA-COFs through MCRs.
Figure 1. PXRD pattern: Pawley refined (blue line), experimental (black dotted line) PXRD patterns with minimum difference (green line) for the hexagonal AA stacking (red) of a) H-QN-TA-COF, b) HO-QN-TA-COF, c) MeO-QN-TA-COF, d) F-QN-TA-COF, e) CF3-QN-TA-COF, and f) COOH-QN-TA-COF. Optimal perspectives of AA stacking in all COFs (Color code: C, light grey spheres; O, red spheres; N, blue spheres, and F, light blue spheres).
Figure 2. a) FTIR spectra of R-QN-TA-COFs; b) Solid-state 13C NMR spectra measured at 10 kHz for R-QN-TA-COFs; c) N2 adsorption–desorption isotherms (77 K) of R-QN-TA-COFs; d) TEM image and crystal lattice spacing of H-QN-TA-COF; e) TEM image and crystal lattice spacing of MeO-QNTA-COF f) Water ??c of R-QN-TA-COFs.
Figure 3. a) UV–vis DRS spectra; b) Mott–Schottky plots; c) Band diagrams; d) Transient photocurrent density; e) EIS Nyquist plots; f) PL fluorescence decay profiles of R-QN-TA-COFs.
Figure 4. a) Photocatalytic H2O2 production rates over R-QN-TA-COFs; b) Comparison of H2O2 production rate over MeO-QN-TA-COF with other documented COFs; c) The photocatalytic H2O2 production over MeO-QN-TA-COF in the presence of water and various sacrificial agents (4 mg of COF in 20 mL of water or 9/1 water/alcohol mixtures); d) AQY of MeO-QN-TA-COF at selected wavelengths (420, 460, 520, 590, and 620 nm); e) SCC efficiency of R-QN-TA-COFs; f) Recyclability test of MeO-QN-TA-COF for photocatalytic H2O2 production.
Figure 5. a) Quenching experiments to determine the ROS; b) EPR spectra of e−; c) EPR spectra of DMPO trapped O2•−; d) EPR spectra of DMPO trapped •OH; e) Adsorption energies of O2 on MeO-QN-TA-COF; f) In situ DRIFTS of MeO-QN-TA-COF during photocatalytic H2O2 production in an air atmosphere.
Figure 6. a) and b) The frontier molecular orbital distributions of model compounds for MeO-QN-TA-COF and CF3-QN-TA-COF; c) and d) Molecular van der Waals surface plotted with electrostatic potential of model compounds for MeO-QN-TA-COF and CF3-QN-TA-COF.
Scheme 2. Reaction mechanism for visible light photocatalytic H2O2 production over MeO-QN-TA-COF.
https://doi.org/10.1002/smll.202411625
