Random　diffusion　of　electrons　and　holes　aggravates　rapid　charge　recombination　and　limits　the　efficiency　of　photocatalytic　processes.　Spin　manipulation　presents　an　efficient　strategy　to　regulate　charge　carrier　behavior.　Herein,　we　successfully　introduced　Cu　into　sulfur　vacancy-rich　Mn0.3Cd0.7S　(MCS-s),　which　effectively　regulates　electron　spin　polarization　and　enhances　the　internal　electric　field　(IEF)　within　the　semiconductor.　Through　coupling　with　phosphomolybdic　acid　hydrate　(HPM)　to　construct　Z-scheme　heterostructure,　we　established　an　efficient　pathway　for　charge　carrier　migration　in　the　photocatalytic　process.　DFT　calculations　and　experimental　results　indicate　that　sulfur　vacancy-induced　IEF　drives　electrons　to　migrate　from　the　bulk　phase　to　surface-vacancy　sites,　which　accelerates　charge　carrier　transport　dynamics　for　efficient　H2　evolution　coupled　with　imine　production.　Remarkably,　the　optimized　HPM/Cuₓ-MCS-s　demonstrated　remarkable　performance　with　imine　production　rates　of　15.4　mmol/g/h,　along　with　a　high　selectivity　of　98.0　%　towards　imine,　achieving　over　19　times　the　rate　of　pristine　MCS-s.　This　work　provides　new　insight　into　the　application　of　polarized　electric　field　regulation　in　bifunctional　photocatalysts.　©　2025　Elsevier　B.V.