Journal Article Review functionality CO2 photoreduction CO2-to-CH4 photoreduction Jahn–Teller effect S-scheme heterojunctions bimetallic co-catalyst regulation charge transfer conjugated carbon nitride polymers crystalline carbon nitride deactivation dimetal Co-Ru atoms directional charge transfer lattice distortion selective CO2 adsorption single‐atom heterogeneous catalysts stability strain structure‐property‐performance structure–property–performance synergistic photocatalysis