Conjugated Organic Polymers with Anthraquinone Redox Centers for Efficient Photocatalytic Hydrogen Peroxide Production from Water and Oxygen under Visible Light Irradiation without Any Additives

Abstract

The photocatalytic generation of hydrogen peroxide (H 2 O 2 ) from H 2 O and O 2 under visible light irradiation is a hopeful approach to achieve solar-to-chemical energy transformation. While the lack of specific redox reaction centers is still the main reason for low photocatalytic H 2 O 2 production efficiency, herein, we present a conjugated organic polymer (AQTEE-COP) containing anthraquinone redox centers by Sonogashira cross-coupling reaction between 2,6-dibromoanthraquinone (AQ) and 1,1,2,2-tetrakis(4-ethynylphenyl)ethene. The extended π-conjugated framework with an electron push−pull effect between electron-donating tetraphenylethene moieties and electron-withdrawing anthraquinone moieties not only broadened the visible light absorption range but also promoted the separation and migration of photo-induced charge carriers. Meanwhile, the anthraquinone moieties can serve as redox centers to accept photoinduced electrons and transfer them to adsorbed O 2 molecules for subsequent H 2 O 2 production. The well-defined structure of AQTEE-COP with task-specific anthracene redox centers provides molecular-level insights into the mechanistic understanding of the photocatalytic H 2 O 2 generation from H 2 O and O 2 . The AQTEE-COP exhibits efficient photocatalytic H 2 O 2 production with an initial rate of 3204 μmol g −1 h −1 under visible light (λ ≥ 400 nm) irradiation without any additional photosensitizers, organic scavengers, or co-catalysts. This article provides a protocol for the rational design of pre-functionalized conjugated organic polymerbased materials for solar-to-chemical energy transformation.

Anthraquinone-Based Conjugated Organic Polymers Containing Dual Oxidation Centers for Photocatalytic H2O2 Production from H2O and O2 under Visible-Light Irradiation

“…This result further suggested that photocatalytic H 2 O 2 production occurs through sequential two-step single electron O 2 reduction, in which • O 2 – acts as an intermediate . The wavelength dependence of photocatalytic generation of H 2 O 2 showed that the trend of H 2 O 2 formation matched well with the absorption spectra of AQTB-COP and AQTT-COP (Figure c), indicating that the production of H 2 O 2 was triggered by light irradiation . For examining the heterogeneity of AQTB-COP and AQTT-COP, thermal filtration experiments proceeded (Figure S10).…”

“…Both AQTB-COP and AQTT-COP exhibited signals at ∼182.1 and ∼91.6 ppm in the solid-state 13 C NMR spectra (Figure b), which are assigned to the carbonyl carbon atoms of anthraquinone moieties and carbon atoms of the internal alkyne moieties, respectively. While the wide peaks between 110 and 150 ppm are ascribed to the carbon atoms on phenyl rings . Moreover, the additional peak at ∼ 169.8 ppm in the solid-state 13 C NMR spectrum for AQTT-COP corresponds to the carbon atoms of the triazine ring.…”

“…As shown in Figure a, the kinetic profiles of AQTB-COP and AQTT-COP showed that the generation of H 2 O 2 increased swiftly in the first half hour and gave rise to the initial rates of 1436 and 3221 μmol g –1 h –1 , respectively, which were higher compared to those of most reported polymer-based photocatalysts (Table S1), and representative C 3 N 4 , COFs, and CTFs-based photocatalysts (Figure ). ,, The yellow of the Ce(SO 4 ) 2 chromogenic reagent disappeared, which visually certified H 2 O 2 production from the photocatalytic reaction of H 2 O and O 2 under visible-light irradiation via AQTT-COP as the photocatalyst (Figure S6). In addition, AQTT-COP exhibited much higher photocatalytic activity, which could be due to the dual oxidation centers of alkynyl and triazinyl moieties in AQTT-COP.…”

Tailoring Heteroatoms in Conjugated Microporous Polymers for Boosting Oxygen Electrochemical Reduction to Hydrogen Peroxide

“…Hydrogen peroxide (H 2 O 2 ), one of the most valuable chemicals, is widely utilized in industries and the medical field . Production of H 2 O 2 via electrochemical 2e – -ORR is a cost-effective and eco-friendly route compared to the energy-intensive synthesis process with a mixture of oxygen and hydrogen and the waste-producing anthraquinone process. − Some carbon-based electrocatalysts such as defective and heteroatom-doping carbon have been developed to drive the corresponding process. , Especially, carbon functionalized by oxygen , (such as ether and carboxylic acids) and nitrogen − (such as graphitic, pyrrolic, and pyridinic nitrogen) exhibited excellent selectivity and productivity of H 2 O 2 . However, preparation under high-temperature pyrolysis not only leads to inevitable energy consumption but also brings impurity constituents, discounting their essential catalytic activity.…”

Enhanced Reducibility via Altering Exciton Binding Energy of Conjugated Microporous Polymers for Photocatalytic Reduction

“…In addition, the open cavity of CMPs is well suited for the binding of small organic molecules, allowing them to access the exposed inner surface, where the transformations occur. Recently, the D–A molecular engineering strategy has been utilized for constructing CMP-based photocatalysts with highly efficient charge separation. − For example, Bojdys et al found that the CMP photocatalyst incorporated stronger D–A interactions with shorter D–A pathways and featured efficient charge separation for water splitting . Despite the extensive research efforts on D–A type CMPs, works dealing with the engineering of D–A interactions and unveiling their influence on exciton binding energy for photocatalytic activity are still rare.…”