Hexagonal Hollow Porous Organic Framework Nanotubes for Efficient Photocatalytic H<sub>2</sub>O<sub>2</sub> Production in Pure H<sub>2</sub>O under O<sub>2</sub> Atmosphere
Xiahong Xu, Yan Sui, Wen‐Tong Chen, Shaohui Xiong, Yuntong Li, Xiaodan Li, Wei Huang, Haibing Zhao, Gangyong Zhou, Hongmei Chen, Hong Zhong
Abstract
The production of hydrogen peroxide (H 2 O 2 ) by combining photocatalytic oxygen (O 2 ) reduction with water (H 2 O) oxidation is a satisfactory substitute for the industrial anthraquinone process. But the photocatalytic efficiency of H 2 O 2 generation is still low, especially in heterogeneous reactions, owing to the poor mass transfer and weak H 2 O oxidation. Hereby, a porous organic framework (BPYTEA-POF) with a hexagonal hollow nanotube structure was synthesized through 5,5′-dibromo-2,2′-bipyridine (BPY) reacting with tris(4-ethynylphenyl)amine (TEA) by the Sonogashira coupling reaction without a template, which contains a 2,2′-bipyridine H 2 O oxidation active site. BPYTEA-POF with hexagonal hollow nanotube morphology and a hierarchical porous wall is beneficial to the mass transfer and/or diffusion of the substrate via a siphonic effect; meanwhile, it benefits exposure of the catalytic active site, which boosts the contact of O 2 and H 2 O with the active site and rapidly dissociates the generated H 2 O 2, thus improving the photocatalytic reaction efficiency. At the same time, the 2,2′-bipyridine moiety is capable of effectually weakening the O–H bonds of H 2 O and promoting the oxidation of H 2 O to produce O 2 and proton (H + ); then, the produced O 2 and H + were used for efficient H 2 O 2 production under additive-free condition. The definite hollow nanotube structure and specific active sites of H 2 O oxidation enhance the initial photocatalytic rate of O 2 and H 2 O to H 2 O 2 by BPYTEA-POF up to 3446 μmol g cat –1 h –1, under the condition of visible-light irradiation (λ ≥ 400 nm) without any additional additive.