Ideal chemical transformations in terms of green and sustainable chemistry convert abundant, low energy starting materials into high value products without losing a single atom.¹ Light-driven catalysis offers tools for such reactions.² We discuss in the lecture key photocatalytic principles and how they can be applied to redox-neutral reactions, such as C-H carboxylations of alkanes and arenes with carbon dioxide.³ Current scope and limitations are shown and a perspective is given where the use of light may lead to better catalysis.⁴