Photocatalytic lignin oils and CO2 upgradation to diesel precursors and syngas over engineered CdSe quantum dots

•With SiO2 light scattering, CdSe QDs/B-SiO2 was prepared by electrostatic self-assembly.•Lignin oils convert to diesel precursors & H2 with noble-metal free catalyst in H2O.•Photocatalytic lignin oils & CO2 convert to diesel precursors & syngas for the first time.•Solvent enhanced light scattering was discovered to promote photocatalytic performance.