Photocatalytic CO2 reduction to methanol: How can the dilemma be solved?

In the context of the upcoming hydrogen technology, methanol can play a crucial role as liquid hydrogen organic carrier and as energy vector. However, for this new role, methanol has to be obtained through a CO2-neutral footprint process. One appealing possibility is the selective solar-light photocatalytic CO2 reduction with H2O. The present opinion highlights the contradiction of methanol being easily oxidized under photocatalytic conditions and its possible formation using photocatalysis. The opinion emphasizes the importance of control experiments, particularly the use of isotopic labeled 13CO2, to firmly support the source of possibly detected methanol. A viable strategy to solve the conundrum is the use of heterojunctions in which the oxidizing component does not show preference for methanol adsorption.