Thiophene‐Containing Covalent Organic Frameworks for Overall Photocatalytic H₂O₂ Synthesis in Water and Seawater

Abstract

H2O2 is a significant chemical widely utilized in the environmental and industrial fields, with growing global demand. Without sacrificial agents, simultaneous photocatalyzed H2O2 synthesis through the oxygen reduction reaction (ORR) and water oxidation reaction (WOR) dual channels from seawater is green and sustainable but still challenging. Herein, two novel thiophene‐containing covalent organic frameworks (TD‐COF and TT‐COF) were first constructed and served as catalysts for H2O2 synthesis via indirect 2e− ORR and direct 2e− WOR channels. The photocatalytic H2O2 production performance can be regulated by adjusting the N‐heterocycle modules (pyridine and triazine) in COFs. Notably, with no sacrificial agents, just using air and water as raw materials, TD‐COF exhibited high H2O2 production yields of 4060 μmol h−1 g−1 and 3364 μmol h−1 g−1 in deionized water and natural seawater, respectively. Further computational mechanism studies revealed that the thiophene was the primary photoreduction unit for ORR, while the benzene ring (linked to the thiophene by the imine bond) was the central photooxidation unit for WOR. The current work exploits thiophene‐containing COFs for overall photocatalytic H2O2 synthesis via ORR and WOR dual channels and provides fresh insight into creating innovative catalysts for photocatalyzing H2O2 synthesis.

Photocatalytic activity enhancement with 4-trifluoromethylphenylacetylene-functionalized Cu2O cubes and rhombic dodecahedra from band structure modulation and use in boronic acid hydroxylation

“…34 Previously, when methanol was also used as the solvent to probe superoxide radical production, a characteristic 6-peak feature in the EPR spectrum was obtained, so superoxide radicals should also form in the photocatalytic process. 22,35 A lower EPR peak intensity for the functionalized octahedra also matches the photocatalysis results. For Cu 2 O rhombic dodecahedra, there is a recognizable decrease in EPR peak intensity with 4-TFMA modification.…”

Unveiling the Dynamic Evolution of Single-Atom Co Sites in Covalent Triazine Frameworks for Enhanced H2O2 Photosynthesis

“…Conversely, Co SA /Py-CTF showing a new vibrational peak at 910 cm –1 attributed to 1,4-endoperoxide intermediate (−O–O−), , suggesting a shift from Pauling-type to Yeager-type O 2 adsorption configuration under light conditions. Furthermore, the emergence of a distinct peak at ∼780 in the quasi in situ Raman spectra (Figure S39) provides additional evidence supporting the existence of the −O–O– intermediate in the H 2 O 2 photosynthesis process facilitated by the Co SA /Py-CTF system. , In addition, the significantly enhanced −OH signal (1300–1374 cm –1 ) derived from H 2 O 2 generation in the Co SA /Py-CTF system . Unlike Co SA /Tr-CTF, where *OOH tends to form ·O 2 – during ORR, the Yeager-type adsorption configuration of O 2 on Co SA /Py-CTF promotes direct conversion to H 2 O 2 via a one-step 2 e – route .…”

Sustainable photocatalytic synthesis of hydrogen peroxide from catechol-formaldehyde resin microspheres modulated by nitrogen-doped carbon dots

“…30,54 It has been discussed that ˙O 2 − can be stabilized by complexation with a Lewis acid and Na + , possibly preventing the reaction of O 2 and H 2 O 2 , resulting in the undesired reduction decomposition of hydrogen peroxide into water. 56 Therefore, we also used saturated sodium chloride solution as the solvent in the photocatalytic system. Unfortunately, the photocatalytic H 2 O 2 production did not increase but rather slightly decreased (Fig.…”