Phosphorus‐Programmed Hollow Carbon Nitride/ZnIn ₂ S ₄ S‐Scheme Microreactors for CO ₂ Photoreduc

Photocatalytic CO ₂ reduction with water offers a route for solar fuels, yet efficiency is restricted by weak CO ₂ activation, rapid charge recombination and loss of redox‐potential in conventional heterojunctions. CH ₄ formation requires sustained multielectron and multiproton transfer. Here we develop a phosphorus‐programmed hollow microreactor composed of phosphorus‐doped hollow carbon nitride (P‐HCNS) and ZnIn ₂ S ₄ (ZIS), coupling light harvesting, charge‐potential retention and gas‐phase reactant transport. ZIS nanosheets are grown in situ on P‐HCNS spheres, creating close semiconductor contact and an interface that promotes charge redistribution upon Fermi‐level equilibration. Under CO ₂ /H ₂ O‐vapor conditions without sacrificial agents or photosensitizers, optimized P‐HCNS/ZIS produces CO and CH ₄ at 689 and 156 μmol g ⁻¹  h ⁻¹ , respectively, corresponding to a combined CO and CH ₄ carbon‐production rate of 845 μmol C g ⁻¹  h ⁻¹ . P _0.25 ‐HCNS/ZIS is optimal among tested loadings; physical‐mixture and solid‐sphere controls support interfacial contact and hollow porosity. DFT reveals interfacial charge redistribution and an electrostatic‐potential difference consistent with an internal electric field. Spectroscopic and photoelectrochemical analyses support a proposed S‐scheme‐type pathway that promotes charge separation and retains reducing electrons for CO ₂ conversion. In situ infrared spectroscopy tracks HCOO ⁻ ‐related surface species associated with the CO/CH ₄ reaction network. Phosphorus‐regulated electronic structure, interfacial charge transfer and hollow architecture enable CO ₂ ‐to‐CO/CH ₄ conversion.