A metal sulfide-based S-scheme homojunction photocatalyst, 2D/3D n-CdIn₂S₄/o-CdIn₂S₄ (n-CIS/o-CIS), was synthesized through a solvothermal method by adjusting the amount of polyvinylpyrrolidone (PVP). This structure exhibits an internal electric field that enhances the separation and migration of photogenerated electron-hole pairs, leading to improved photocatalytic activity and stability in the selective oxidation of phenylcarbinol (PhCH₂OH) to benzaldehyde (PhCHO) under visible light. The n-CIS/o-CIS composite shows a high production rate of PhCHO (up to 19.9 mmol g⁻¹ h⁻¹), significantly higher than pure n-CIS and o-CIS samples. The S-scheme homojunction configuration ensures efficient charge separation and transport, with electrons and holes being spatially separated for photocatalytic reactions. The n-CIS/o-CIS homojunction also demonstrates excellent photostability, with minimal degradation after multiple cycles. The study highlights the importance of controlling charge carrier separation and migration for enhancing photocatalytic performance in redox-driven reactions. The n-CIS/o-CIS photocatalyst is effective for the selective oxidation of various aromatic alcohols into corresponding aldehydes. The results confirm the S-scheme charge transfer mechanism, with both superoxide radicals (•O₂⁻) and photogenerated holes (h⁺) playing key roles in the oxidation process. The n-CIS/o-CIS homojunction is a promising candidate for solar energy conversion and selective organic transformations.A metal sulfide-based S-scheme homojunction photocatalyst, 2D/3D n-CdIn₂S₄/o-CdIn₂S₄ (n-CIS/o-CIS), was synthesized through a solvothermal method by adjusting the amount of polyvinylpyrrolidone (PVP). This structure exhibits an internal electric field that enhances the separation and migration of photogenerated electron-hole pairs, leading to improved photocatalytic activity and stability in the selective oxidation of phenylcarbinol (PhCH₂OH) to benzaldehyde (PhCHO) under visible light. The n-CIS/o-CIS composite shows a high production rate of PhCHO (up to 19.9 mmol g⁻¹ h⁻¹), significantly higher than pure n-CIS and o-CIS samples. The S-scheme homojunction configuration ensures efficient charge separation and transport, with electrons and holes being spatially separated for photocatalytic reactions. The n-CIS/o-CIS homojunction also demonstrates excellent photostability, with minimal degradation after multiple cycles. The study highlights the importance of controlling charge carrier separation and migration for enhancing photocatalytic performance in redox-driven reactions. The n-CIS/o-CIS photocatalyst is effective for the selective oxidation of various aromatic alcohols into corresponding aldehydes. The results confirm the S-scheme charge transfer mechanism, with both superoxide radicals (•O₂⁻) and photogenerated holes (h⁺) playing key roles in the oxidation process. The n-CIS/o-CIS homojunction is a promising candidate for solar energy conversion and selective organic transformations.