Reactive oxygen species (ROS), including singlet oxygen (1O2), hydroxyl radicals (•OH), and superoxide anions (O2•−), are highly reactive molecules that play central roles in many chemical, biological, and environmental processes due to their strong oxidative power [1]. Generating ROS in a controlled manner under mild conditions is essential for achieving selective oxidation reactions. Light-driven methods are especially appealing for this purpose, as they offer precise control over where and when ROS are produced.
In recent years, organic materials such as covalent organic frameworks (COFs) and artificial light-harvesting systems (LHSs) have shown great promise as platforms for ROS generation. COFs are crystalline materials made up of organic molecules connected through covalent bonds. Their highly tunable structures and excellent stability make them strong candidates for light-based (photoactive) applications [2]. By designing COFs with photoresponsive components, units that respond to light, it is possible to improve their ability to generate ROS efficiently. Similarly, LHSs mimic the way natural photosynthesis captures and uses light energy [3]. By carefully designing their structure, these systems can serve as powerful photosensitizers, effectively boosting ROS-driven photocatalytic reactions.
To address the ongoing challenge of developing efficient photocatalysts for various oxidation reactions, Zhao, Li, and co-workers introduced a clever approach that combines two photoactive units, triphenylamine (TPA) and porphyrin, into a single COF [4]. The new material, named TFPA-TAPP-COF (Figs. 1a and b), has a well-organized three-dimensional structure with permanent porosity, created through Schiff-base condensation. Structural and light-related tests confirmed the successful incorporation of the two chromophores, which impart the COF semiconducting properties and the ability to generate both 1O2 and O2•− when exposed to visible light. This was confirmed by electron paramagnetic resonance (EPR) measurements.
Notably, this integrated design shows a significant boost in photocatalytic efficiency for a wide range of aerobic oxidation reactions. These include the oxidation of alkylbenzenes, silanes, and thioanisoles, as well as cross-dehydrogenative coupling (CDC) reactions (Fig. 1c). When compared to the individual components, the COF shows much higher activity, thanks to the cooperative interaction between the two photochromic units. Moreover, recyclability tests demonstrated that the COF maintains its structure and efficiency even after several catalytic cycles. Supported by experimental data and theoretical models, this study offers a strong example of how carefully combining complementary photoactive units can create COFs with multifunctional photocatalytic properties, making them useful for a wide range of oxidation reactions.
In a follow-up study, Zhao, Li, and co-workers developed a structurally novel COF, named PyNTB-COF (Fig. 2a), by linking photochromic TPA and pyrene units through imidazole bonds formed in situ [5]. This approach produced a rare donor–acceptor–π–acceptor–donor (D–A–π–A–D) architecture embedded in a crystalline, porous, and stable framework. The incorporation of a D–A–π–A–D architecture markedly enhanced photoinduced charge separation and migration, leading to efficient photocatalytic aerobic oxidation.
PyNTB-COF displayed semiconducting properties and strong sensitivity to visible light, efficiently generating O2•− as verified EPR spectroscopy. Photocatalytic tests showed excellent performance in aerobic oxidation reactions (Fig. 2b). For example, toluene was oxidized to benzoic acid with a 93% yield, and aldehydes underwent oxidative amidation with tetrahydropyrrole to produce amides in 85% yield. These findings highlight the potential of D–A–π–A–D-type COFs in diverse oxidative applications. This study demonstrates that extending π-conjugation in donor–acceptor frameworks not only improve charge transport but also significantly boost photocatalytic performance, laying the groundwork for the development of advanced COF-based catalysts.
To mimic the complex, multi-step energy transfer processes found in natural photosynthesis, Xing and co-workers designed an artificial LHS in water using a self-assembled supramolecular complex [6]. A piperazine-based molecule (PPE-BPI) exhibiting aggregation-induced emission (AIE) was combined with cucurbit[7]uril (CB[7]) to form a stable donor complex via host–guest interactions (Fig. 3). This served as the basis for constructing a three-step energy transfer cascade. By introducing three fluorescent dyes, Eosin B (EsB), Sulforhodamine 101 (SR101), and Cyanine 5 (Cy5), the researchers achieved a directional energy relay from the PPE-BPI-2CB[7] complex through each dye in sequence. Impressively, the system demonstrated high energy transfer efficiency at every step. As energy moved through the cascade, the generation of O2•− progressively increased, enabling efficient photocatalytic oxidation of N-phenyltetrahydroisoquinoline in water. After 18 h of visible light exposure, the system produced an 86% product yield. This work offers a promising biomimetic approach for building multi-step energy transfer systems in aqueous environments, with potential applications in photocatalysis and artificial photosynthesis.
In summary, this editorial highlights recent progress in the design of organic materials for light-driven ROS generation in photocatalysis. By integrating photoresponsive units into COFs and artificial LHSs, researchers have achieved fine control over ROS production, such as 1O2 and O2•−, under mild, visible-light conditions. The use of dual chromophores and extended π-conjugated donor–acceptor systems in COFs has led to enhanced charge separation, charge mobility, and catalytic activity in a wide range of aerobic oxidation reactions. At the same time, advances in supramolecular LHSs illustrate the power of multi-step energy transfer to drive efficient photocatalysis in water. Together, these studies showcase the potential of organic materials as versatile and tunable platforms for ROS-mediated catalysis, paving the way for future innovations in sustainable and selective oxidation chemistry.
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Qing Liu: Writing – original draft. Tangxin Xiao: Writing – review & editing, Supervision, Conceptualization. Zhouyu Wang: Writing – original draft. Leyong Wang: Writing – review & editing, Supervision, Funding acquisition.
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Figure 1 (a) Chemical structure of TFPA-TAPP-COF. (b) Simulated structure of TFPA-TAPP-COF in topological model and illustration of ROS generation. (c) Photocatalytic aerobic oxidation of alkylbenzene, silanes, and thioanisoles, as well as CDC reaction based on TFPA-TAPP-COF. Reproduced with permission [4]. Copyright 2025, Wiley Publisher.
Figure 2 (a) Schematic diagram for the synthesis of PyNTB-COF and the formation of the D-A-π-A-D fragment. (b) Proposed mechanisms of two types of aerobic oxidation reactions photocatalyzed by PyNTB-COF. Reproduced with permission [5]. Copyright 2025, American Chemical Society.
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