Photochemical energy storage in a spatially organized zeolite-based photoredox system

Zeolites are often employed as organizational media or supports for entrapped or adsorbed transition-metal catalysts and photo-catalysts1–6. In such applications, the individual catalytic species have been associated with the framework structure of the zeolite in a purely statistical (randomized) arrangement. A synthetic strategy developed recently7 has shown how a much higher level of organization can be obtained, so pointing the way to the generation of systems in which two or more active components can be arranged—both spatially and in terms of reactivity— within the zeolite host to enhance the efficiency of a desired catalytic reaction. Here we describe an application of this approach to photochemical storage of light energy. Such an application requires efficient photoinduced charge transfer between donor and acceptor molecules to form long-lived charge-separated states: the competing thermal back electron transfer reaction must be minimized. This is achieved in our system by arranging the active components (donor, acceptor and a 'sensitizing' intermediate molecule) such that they occupy adjacent cages within the zeolite framework, and results in unprecedented levels of net charge-separation efficiency.