PROSPER's overarching outcome will be the availability of knowledge-based design guidelines for industrial-relevant application cases, together with strategies for scale-up and a safe long-term operation, ultimately leading to the broad application of photochemistry on an industrial scale. PROSPER will setup a tailored network to train the next generation of experts on fundamentals, design principles and application of industrial-scale photoreactors through comprehensive education on a broad portfolio of topics related to photochemical processes and through hands-on training on industrially relevant research topics. By this, the industrial and academic partners of PROSPER will overcome implementation hurdles and enable the chemical industries’ transition towards sustainable production. The main scientific objectives are: 1. to develop standardized methods for measuring the photon flux and characterizing radiation fields, 2. to understand the impact of mass and heat transport effects on the performance of photoreactors as a basis for developing novel industrial photoreactors for sustainable processing and process intensification, 3. to establish reaction control strategies which maximize photon use efficiency and enable long-term operation, 4. to elucidate safety requirements for photochemical processes and 5. to develop a knowledge-base on photochemical reactor and processes development, containing design guidelines and principles together with performance criteria for photoreactors to enable a knowledge-driven development and scale-up, eventually leading to standard reactor designs. Joint interdisciplinary research by academic and industrial partners will be realized by excellent training through a high-quality, cross-sectional research network including 6 internationally reputed research institutions and 4 leading companies to train experts on photoreactor design with special focus on application at the interface between academic and industrial research.