The framework of solar-to-chemical energy conversion is mapped by an exploding investigation space, aiming at rapid elevation of the technology to commercially relevant performances and processing conditions. Prospective materials and alternative oxidative pathways are revolutionizing water-splitting into decoupled hydrogen and high-value added chemicals production. Yet, pioneering solar refinery systems have been limited to either efficient, but isolated half-reactions or sluggish simultaneous red-ox transformations, hampering the forthcoming adoption of this promising solar-harvesting strategy. Here, we provide the first demonstration of efficient and stable full-cycle redox transformations, synthesising solar chemicals. The identification of a successful redox cycle ensued from fluorescent quenching screening, which bridges between optoelectronic material properties and photosynthetic activity. Implementing this approach on hybrid nanorod photocatalysts (CdSe@CdS–Pt), we demonstrate hydrogen production with photon to hydrogen quantum efficiencies of up to ~70%, under visible light and mild conditions, while simultaneously harvesting solar chemical potential for valuable oxidative chemistries. Facile spectrophotometric analyses further show robust photo-chemical and colloidal stability, as well as product selectivity when converting molecules carrying amino- and alcohol-groups, with solar-to-chemical energy conversion efficiencies of up to 4.2%. As such, rigorous spectroscopic assessment and operando characterization yield superior photosynthetic performance, realizing a truly light-triggered catalytic reaction and establishing nanostructured metal-chalcogenide semiconductors as state-of-the-art artificial photo-chemical devices. Towards Solar Factories, following Ciamician's Dream (Science, 1912): “Forests of glass tubes will extend over the plains and glass buildings will extend everywhere; inside of these will take place the photochemical processes that hitherto have been the guarded secret of the plants”. Display omitted •Photosynthetic solar-to-chemical (STC) energy conversion entails fuels and valuable chemicals production.•4.2% STC conversion efficiency demonstrates a practical route beyond overall water splitting.•Hybrid semiconductor nanorods allow highly efficient operation in mild condition without sacrificial reagent.•Spectro-photometric screening and analyses unravel long-term chemical and colloidal stability.