The　design　of　advanced　metal–organic　framework　(MOF)　catalysts　for　solar-driven　conversion　of　CO2　into　syngas　(CO/H2　mixture)　is　beneficial.　Herein,　the　design　of　a　joint　MOF　heterostructure　consisting　of　orderly　assembled　CoII-　and　CoIII-based　Prussian　blue　analogs　(PBAs)　driven　by　their　spontaneous　lattice　match　in　the　growth　process　is　reported.　As-prepared　H/CoIII-PBA@CoII-PBA　cage　is　a　mesocrystal　and　exhibits　superior　photocatalytic　syngas　production　activity　(VCO　up　to　50.56　mmol　g−1　h−1,　CO/H2　=　1:1),　which　is　among　the　best　state-of-the-art　heterogeneous　photocatalysts　in　the　literature.　Theoretical　calculations　and　experimental　results　confirm　that　CoIII-PBA　exerts　a　stronger　affinity　for　CO2　molecules　than　CoII-PBA,　thus　serving　as　the　active　site.　The　built-in　electric　field　in　the　CoIII-PBA@CoII-PBA　heterojunction　can　direct　the　fast　transport　of　photogenerated　electrons　from　CoII-PBA　to　the　active　CoIII-PBA.　In　the　present　case,　the　engineering　of　electronics　outweighs　morphological　engineering　to　enhance　the　catalytic　properties　of　CoIII-MOF@CoII-MOF　for　CO2-to-syngas　conversion.　©　2023　The　Authors.　Small　Science　published　by　Wiley-VCH　GmbH.