Photo‐Driven Quasi‐Topological Transformation Exposing Highly Active Nitrogen Cation Sites for Enhanced Photocatalytic H₂O₂ Production

Abstract

Herein, the exposure of highly‐active nitrogen cation sites has been accomplished by photo‐driven quasi‐topological transformation of a 1,10‐phenanthroline‐5,6‐dione‐based covalent organic framework (COF), which contributes to hydrogen peroxide (H2O2) synthesis during the 2‐electron O2 photoreduction. The exposed nitrogen cation sites with photo‐enhanced Lewis acidity not only act as the electron‐transfer motor to adjust the inherent charge distribution, powering continuous and stable charge separation, and broadening visible‐light adsorption, but also providing a large number of active sites for O2 adsorption. The optimal catalyst shows a high H2O2 production rate of 11965 μmol g−1 h−1 under visible light irradiation and a remarkable apparent quantum yield of 12.9 % at 400 nm, better than most of the previously reported COF photocatalysts. This work provides new insights for designing photo‐switchable nitrogen cation sites as catalytic centers toward efficient solar to chemical energy conversion.

Regulating Benzene Ring Number as Connector in Covalent Organic Framework for Boosting Photosynthesis of H2O2 from Seawater

“…A comparison in both the H 2 O 2 production rate and raw material cost among reported COF photocatalysts and our cases is shown in Figure b. It is clear that our COF photocatalysts show a comparable H 2 O 2 production rate with most reported COF photocatalysts − but the lowest raw material cost among all reported COF photocatalysts, thereby implying the outstanding advantage of our photocatalysts in industrial application. Catalytic stability represents another factor for industrial application.…”

“…Mott–Schottky (MS) analysis (Figure S5 and S6) was used to estimate the lowest unoccupied molecular orbital (LUMO) level, which gave −0.52 V for ECUT-COF-30 and −0.86 V for ECUT-COF-31. Note that the LUMO levels are more negative than the reduction potential of the oxygen reduction reaction (ORR) in the direct 2e – (+0.68 V) or stepwise 1e – (−0.33 V) fashion (Figure S7), which suggests that our photocatalysts are thermodynamically favorable for photosynthesis of H 2 O 2 through an ORR route. − Moreover, on the basis of the equation E HOMO = E LUMO + E g , we can obtain the highest occupied molecular orbital (HOMO) level of 1.35 V for ECUT-COF-30 and 1.09 V for ECUT-COF-31 (Figure S7), which excludes the possibility of of H 2 O 2 production through water oxidation reaction (WOR, +1.76 V). − …”

Custom‐Design of Strong Electron/Proton Extractor on COFs for Efficient Photocatalytic H2O2 Production

“…In situ diffuse reflectance infrared Fourier transform spectrum (DRIFTS) of SO 3 H‐COF (Figure 5b) exhibits O−O (886 cm −1 ), • O 2 − (1180 cm −1 ), and OOH ad (1288 cm −1 ) vibrations under light irradiation [9d,24] . Moreover, the intensities of these peaks for SO 3 H‐COF increase and become more pronounced than that of H‐COF with irradiation time, suggesting that the incorporation of SO 3 H groups can enhance O 2 adsorption and accelerate the formation of the intermediates, therefore boosting the O 2 ‐to‐H 2 O 2 transformation.…”

Regulating the H2O2 Photosynthetic Activity of Covalent Organic Frameworks through Linkage Orientation

“…Most research spots were focused on exploring effective catalytic active units for photocatalytic H 2 O 2 synthesis. By logically designing or transforming to appropriate units and sites on the skeletons of COFs, such as (diarylamino)­benzene, pyridine, heptazine, piperazine, triazine and quinoline, benzothiazole, acetylene, pyrene, azole, , sulfone, diazine, and so on, − the H 2 O 2 photoproduction performances and corresponding reaction paths can be modulated. Recently, our group also constructed thiophene-containing COFs for H 2 O 2 photosynthesis through ORR and WOR dual channels .…”