Harnessing Water in Photochemical Synthesis: Organization, Confinement, and Sustainable Reactivity

Photochemical synthesis enables bond construction with exceptional spatiotemporal control under mild and energy-efficient conditions. When performed in water, these advantages are amplified, offering a genuinely sustainable reaction platform. Although aqueous media have traditionally constrained photochemical scope, recent advances in reaction engineering, catalytic design, and reactor technologies have rapidly expanded accessible transformations. This review highlights progress in micellar photocatalysis, aquaphotocatalysis, and photoenzymatic/ biohybrid systems, illustrating how water actively shapes reactivity through polarity, interfacial organization, and proximity effects. Together with developments in flow chemistry and automation, these approaches position aqueous photochemistry as a versatile and scalable paradigm for future green synthesis.