Photocatalysis holds great promise to enable sustainable chemical processes related to, for example, the production of renewable fuels or prevention of pollution through advanced oxidation. However, despite significant progress and continuing interest from academia, industry and policy makers, key challenges have to be overcome. First, ideal photocatalytic materials should obey stringent requirements related to stability, cost, bandgap compatibility, availability of raw materials, and photon efficiency. In spite of certain limitations, such as an undesirable band gap, titania remains the frontrunner in terms of research and commercial applications. This chapter briefly discusses strategies to expand the allowable bandgap of photocatalytic materials. A key focus is on the use of metal–organic frameworks (MOFs). MOFs have an organic–inorganic structure, exhibit a high surface area and can be tuned with tremendous flexibility, which makes them promising candidates to advance photocatalysis. Second, the development of photocatalytic reactors is discussed. The design and operation of photocatalytic reactors is not trivial due to requirements for efficient contact of reactants with the catalyst and efficient utilization of photons. The former requirement is common for any heterogeneous catalytic reactor whereas the latter is unique for photocatalysis. Consequently, numerous reactor configurations have been designed specifically for photocatalysis of which a selection is reviewed in this chapter. Recent advances in simulation and optimization of mathematical models of photocatalytic reactors offer an important support for design. Furthermore, novel solid-state light sources provide opportunities for increased robustness, reduced costs and improved flexibility for the design and operation of future photocatalytic reactors.chemistry has been investigated for nearly thirty years with many notable results being published on apparent process enhancement due to microwave exposure. Conclusive proof of beneficial microwave-chemical interactions is lacking though, as are design rules for successful implementation of microwave-chemical processing systems. In this chapter, the main cause for this is asserted to be the current absence both of suitable instrumentation for research, and processing equipment that merges chemistry with electromagnetic aspects. Several concepts are presented to show how these challenges may be addressed.@en

The complicated interplay between mass and photon transfer within a photocatalytic reactor calls for an integrated design approach. A model-based optimization approach for LED-based photocatalytic reactors is presented. First, a model that describes the distribution of reactants and photons within a photocatalytic reactor is developed. Then, several design variables related to the reactor dimensions and light sources are optimized simultaneously using the photocatalytic degradation of toluene as a model system. The results demonstrate how different formulations of the problem can be used to either minimize the reactor cost or to obtain a specified concentration profile within the reactor.

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