Industrially, aldehydes are produced annually on a multimillion-tonne scale via the hydroformylation of olefins with syngas (CO/H2 mixture). Nonetheless, this transformation has not found frequent use in the laboratory. Here we report on a simple strategy for the concerted generation of syngas from two accessible and crystalline main element compounds with just water as the primary activator for syngas release. By decoupling the syngas formation and consumption via a two-chamber reactor we demonstrate this low-pressure, low-temperature and near-stoichiometric hydroformylation operates efficiently on a diverse array of terminal olefins without the need for expensive equipment. Our approach provides unique opportunities to access aldehydes in a safe and reliable manner with further adaptation to the synthesis of a range of pharmaceuticals and relevant molecules thereof. This strategy is adaptable to carbon isotope labelling as demonstrated by the use of a 13CO releasing molecule. We anticipate this hydroformylation approach will provide a complementary toolbox for drug discovery and development. [Figure not available: see fulltext.].