北京大学童美萍Angew：含氰COFs从水、空气和阳光中光合成过氧化氢
第一作者北京大学Yanghui Hou、北京大学深圳研究生院Peng Zhou，通讯作者北京大学童美萍在《Angewandte Chemie International Edition》发表题为《Efficient Photosynthesis of Hydrogen Peroxide by Cyano-Containing Covalent Organic Frameworks from Water, Air and Sunlight》重要成果！
This work not only provides new insights into the design of COFs by regulating the amount of charge transfer channels and enhancing the rate-determining two-electron water oxidation to boost H2O2 photosynthesis, but also paves the way for the practical application of COFs-based photocatalysts in solardriven synthesis.
激子(e—h+对)分离/转移不足和双电子水氧化迟缓是限制COFs光催化剂H2O2光合效率的两个主要因素。在此，作者提出了一种替代策略，同时促进激子分离/转移，并通过双氨基官能化降低COFs中双电子水氧化的能量垒。原位表征和理论计算表明，双氰基功能化提高了COF-0CN供体和受体单元之间的电荷转移通道的数量，从未氰基功能化的COF-0CN的2个增加到单氰基功能化的COF-1CN的3个和双氰基功能化的COF-2CN的4个，导致COF-2CN的分离/转移效率最高。更重要的是，在H2O2光合作用中，双氰基激活邻近的C原子，产生关键的*OH中间体，有效地降低了决定速率的双电子水氧化的能垒。在可见光照射下，COF-2CN同时增强了激子分离/转移和双电子水氧化，在不使用牺牲试剂的情况下，水和氧的H2O2产率高达1601 μmol g-1 h-1。COF-2CN可以在较宽pH范围的水中、不同的实际水样中、在自然阳光照射下的放大反应器中、在连续流反应器中连续产生H2O2溶液进行水净化等条件下有效产出H2O2。
Figure 1. Chemical structure of COF-0CN (a), COF-1CN (b) and COF-2CN (c). Experimental and simulated PXRD patterns of COF-0CN (d), COF-1CN (e) and COF-2CN (f).
Figure 2. Electrostatic potential surface of COF-0CN (a), COF-1CN (b) and COF-2CN (c), the insets show the corresponding charge transfer channels where the green sphere (denoted by green D), bule sphere (denoted by bule A), and red sphere (denoted by red A) represent biphenyl, β-ketoenamine ring, and cyano group, respectively. Photocurrent responses (d), fluorescence lifetime decay spectra (e), and integrated PL intensity as a function of temperature (f) of three COFs. 2D mapping TA spectra of COF-0CN (g), COF-1CN (h) and COF-2CN (i).
Figure 3. Photosynthesis of H2O2 by the fabricated COFs, g-C3N4 and P25 (a). The comparison of H2O2 photosynthesis rate by COF-2CN with other reported photocatalysts under similar measurement conditions (b). The apparent quantum yield (AQY) of COF-2CN as a function of wavelength (c). The reusability of COF-2CN for H2O2 photosynthesis (d). The effects of initial solution pH on H2O2 yield by COF-2CN under visible-light irradiation (e). Photocatalytic H2O2 yield by COF-2CN in ultrapure water, tap water, river water, lake water and sea water under visible-light irradiation (f). Photosynthesis of H2O2 by COF-2CN in a continuous-flow reactor (g). Photograph of the scaled-up reactor under natural sunlight irradiation (h) and the corresponding photocatalytic H2O2 yield for 5-reused cycles by COF-2CN with natural sunlight irridation (i).
Figure 4. Quenching experiments for H2O2 photosynthesis (a). The ·O2−yield of three COFs detected by NBT method (b). Time-course in-situ FTIR spectra of COF-2CN under visible-light irradiation with O2 (c). PDOS of three COFs (d). Calculated energy profile for oxidation of water into H2O2 (e) and reduction of oxygen into H2O2 (f) on three COFs at U = 0 V vs. SHE at pH = 7.
Efficient Photosynthesis of Hydrogen Peroxide by Cyano- Containing Covalent Organic Frameworks from Water, Air and Sunlight
https://doi.org/10.1002/anie.202318562