Weakly Hydrophilic Imine-Linked Covalent Benzene–Acetylene Frameworks for Photocatalytic H₂O₂ Production in the Two-Phase System

Abstract

Conversing oxygen (O2) to hydrogen peroxide (H2O2) driven by solar energy is a promising H2O2 onsite production route but often short of efficient and durable photocatalysts. Herein, strong π–π conjugate polycyclic aromatic benzene and acetylene units have been constructed into new covalent organic frameworks (COFs) linked by imine CN bonding. These COFs demonstrated two-dimensional hexagonal crystalline frameworks with higher crystallinity and larger surface area (>600 m2 g–1). Covalent benzene–acetylene frameworks possessed appropriate visible light-responsive band structure and the suppressed charge recombination rate. The −OH groups on their frameworks enable them to be weakly hydrophilic. As a result, it served as high-performance but durable photocatalysts for H2O2 production in the water–benzyl alcohol (BA) two-phase system. It delivered a H2O2 production rate of 1240 μmol h–1 gcat –1 and durable catalytic efficiency within 60 h, comparable to the best COF-based catalysts. This study provides an efficient two-phase photocatalytic system for H2O2 production based on weakly hydrophilic imine-linked benzene–acetylene organic photocatalysts.

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

“…Wavelength‐dependent H 2 O 2 evolution shows that the photocatalytic activity of PD 2+ ‐COF 16.7 matches its absorption spectrum (Figure 4c), which indicates the H 2 O 2 production is a photo‐induced chemical reaction process. The calculated apparent quantum yield of PD 2+ ‐COF 16.7 is 12.9 % at 400 nm, exceeding most of the previously reported COF‐based photocatalysts for 2‐electron ORR toward H 2 O 2 production (Figure 4d, Table S8 and S9) [3,7,27,43–52] . PD 2+ ‐COF 16.7 was reused over four cycles without noticeable deactivation (Figure 4e).…”

“…The calculated apparent quantum yield of PD 2 + -COF 16.7 is 12.9 % at 400 nm, exceeding most of the previously reported COF-based photocatalysts for 2-electron ORR toward H 2 O 2 production (Figure 4d, Table S8 and S9). [3,7,27,[43][44][45][46][47][48][49][50][51][52]] PD 2 + -COF 16.7 was reused over four cycles without noticeable deactivation (Figure 4e). Its composition and chemical structure of PD 2 + -COF 16.7 could be well maintained (Figure S24-S26, Table S10) after the long-term cycling, suggesting the robust durability that is required for sustainable H 2 O 2 evolution.…”

Carbonized Polymer Dots/Bi/β-Bi2O3 for Efficient Photosynthesis of H2O2 via Redox Dual Pathways

“…40 The peak at 1067 cm −1 corresponds to the symmetric CO 3 2− stretching motion. 36 For CBO-1905, except for A 1 (1) , B 1 and A 1 (2) modes of Bi−O, the Dand G-bands of carbonaceous materials are located in the range of 800−2000 cm −1 . Its enlarged view is shown in Figure 3c.…”

“…Four vibrational modes are shown in the Raman spectra of β-Bi 2 O 3 (Figure 3b). A 1 (1) (90 cm −1 ) and B 1 (123 cm −1 ) are attributed to the external vibrations of the Bi−O bond, while A 1 (2) (312 cm −1 ) and A 1 (3) (447 cm −1 ) belong to its internal vibrations. 39 In Bi 2 O 2 CO 3 , the peaks at 71 and 162 cm −1 are assigned to shifts in the Bi and O atoms, respectively.…”

Linker length-dependent hydrogen peroxide photosynthesis performance over crystalline covalent organic frameworks

“…BDPA containing electron-donor alkyne units and hydrophilic hydroxyl group were chosen as aldehyde building blocks, which showed better photocatalytic H 2 O 2 production performance confirmed by us and other authors. 10,22 After reacting BDPA with these para diamines, three new imine-linked COFs (COF-BPDA-DTP, -BD and -PA) were successfully prepared. These COFs possessed similar molecule structures but with different linker lengths.…”