Covalent organic frameworks (COFs), as one of the most significant members of the porous organic frameworks, have been well used in the photocatalysis owing to their outspread π-conjugated framework, high crystallinity and regular pore structure. Herein, after reducing the labile imine-linked COF-300 to the more stable aminelinked COF-300-AR, we for the first time demonstrated that COF-300-AR was the light-responsive oxidase mimic. COF-300-AR exhibited excellent oxidase-mimicking activity under purple light stimulation (λ = 400 nm), which can catalyze the oxidation of classical substrates such as 3,3′,5,5′-tetramethylbenzydine (TMB) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) by the formation of • OH and O 2•− free radicals in the presence of dissolved oxygen. The COF-300-AR oxidase mimic has outstanding advantages of easy light control, high stability, good reusability, and highly catalytic oxidation capacity and has been applied to detect glutathione (GSH) levels in HL60 cells with good selectivity and high sensitivity. This study will broaden the sensing applications of COFs and offer a promising build block for the construction of artificial enzymes.

We present herein a method for the controllable synthesis of 3-aryl-benzomorpholine and 2-aryl-benzomorpholine cycloadducts via cross-coupling/annulation between electron-rich 2-aminophenols and 4-vinylphenols.

The bioinspired synthesis of heterodimer neolignan analogs is reported by single-electron oxidation of both alkenyl phenols and phenols individually, followed by a combination of the resultant radicals. This oxidative radical cross-coupling strategy can afford heterodimer 8−5′ or 8−O−4′ neolignan analogs selectively with the use of air as the terminal oxidant and copper acetate as the catalyst at room temperature.

An environmentally friendly and highly diastereoselective method for synthesizing indanes has been developed via a metastable-state photoacid system containing catalytic protonated merocyanine (MEH). Under visible-light irradiation, MEH yields a metastable spiro structure and liberated protons, which facilitates the formation of carbocations from benzyl alcohols, thus delivering diverse molecules in the presence of various nucleophiles. Mainly, a variety of indanes could be easily obtained from benzyl alcohols and olefins, and water is the only byproduct.

During the past decade, transition metal-catalyzed dehydrogenative cross-couplings have emerged as an attractive strategy in synthetic chemistry due to its high step-and atom-economy as well as the less functionalized coupling partners. However, such reactions have to always use stoichiometric amount of sacrificial oxidants such as peroxides, high-valent metals (Cu salts, Ag salts, etc.), or iodine(III) oxidants, thereby leading to possible generation of toxic wastes and making the process less desirable from a green chemistry perspective. The recently developed photocatalytic CCHE (cross-coupling hydrogen-evolution) reactions are a conceptually new type of reactions enabled by combination of photo-redox catalysis and proton reduction catalysis, wherein the photocatalyst uses light energy as the driving force for the cross-coupling and the hydrogen evolution catalyst may capture electrons and protons from the substrates or reaction intermediates to produce molecular hydrogen (H 2). Thus, without use of any sacrificial oxidant and under mild conditions, the dual catalyst system may afford cross-coupling products with excellent yields and an equivalent amount of H 2 as the sole byproduct. This kind of cross-coupling delivers a greener synthetic strategy and is particularly useful for reactions that involve species sensitive to traditional oxidants. In CCHE reactions, the raw materials are directly converted into products and hydrogen, the reactions are highly atom economy, environmentally friendly, and have attractive potential industrial application prospects. In this review, recent dramatic developments of photocatalytic and electrochemical CCHE reactions are discussed via the most prominent mechanistic pathways, the types of CC bond, C-X (heteroatom) bond, or X-X bond formations and specific reaction classes.