Copper catalyzed sun fuel generation by CO2 and H2O reduction Heterogeneous copper based catalysts have been investigated for the photocatalytic H2O and CO2 reduction. Ex situ and in situ synthesized catalysts supported on inert silica have been developed for the photocatalytic proton reduction. The best supported photocatalyst achieved a significantly higher activity compared to the initial homogeneous precursor. In a second project highly porous photocatalysts have been synthesized applied in aqueous CO2 reduction and characterized by in situ XAS EPR and UV vis measurements. An improved catalytic performance was observed by the addition of oxygen.<eng>