During the last decades, the engineering of chemical processes has focused more and more on energy efficiency and reduction of climate-changing emissions. Regarding the synthesis of aldehydes, the photocatalytic dehydrogenation of alkanes to olefins, using visible (sun) light, and the subsequent hydroformylation of such olefins with CO2 seem to be capable to achieve both targets. This work deals mainly with catalyst concepts for both reaction steps. Here, kinetic studies of the photocatalytic alkane dehydrogenation are presented, and the feasibility of hydroformylation using CO2 is described in a continuous gas phase reaction. The problems that have to be solved befoe the technical application are discussed and an economic and ecological evaluation for both processes is carried out.