Shining a light on benzo[c][1,2,5]thiadiazole photocatalysts

The benzo[ c ][1,2,5]thiadiazole ( BTZ ) group is a strongly electron accepting unit that has primarily been investigated for application in photovoltaic systems or as fluorescent bioimaging agents or sensors. The strongly electron accepting nature of the BTZ group, in combination with its excellent photostability and options for chemical derivatisation, has kindled interest within the photochemistry community with regards to using this unit as a prospective building block in π -conjugated electron donor-acceptor photocatalysts. The aim of this review is to highlight the research surrounding the development of photocatalytic systems based on the BTZ group. This will include discussing chemical reactions that can be used to synthesise or derivatise the BTZ motif, as well as highlighting methods that have been used to alter the structural, photophysical or optoelectronic properties of electron donor- BTZ electron acceptor systems. Subsequent discussion of the photocatalytic applications will span both homogeneous photocatalysts (molecules, molecular cages and linear polymers) and heterogeneous materials (such as crosslinked organic polymers, covalent organic frameworks, and metal-organic frameworks) containing the BTZ group and structurally related groups. • Benzo[c][1,2,5]thiadiazole (BTZ) is a robust electron acceptor building-block with excellent photostability and synthetic tunability, making it ideal for photocatalyst design. • The review discusses synthetic methods for preparing and functionalising BTZ-based structures to modify their structural, photophysical, and optoelectronic properties. • Applications of BTZ-containing systems are explored in both homogeneous photocatalysts (e.g., molecules, polymers) and heterogeneous platforms (e.g., COFs, MOFs). • Design strategies and structure-property correlations are emphasised to optimise the photocatalytic performance of BTZ-based materials. • BTZ-based photocatalysts are emphasised as a promising strategy for advancing sustainable chemical processes, with potential applications in 3D printing and continuous photochemical processes in flow chemistry.