K/Co co-doped carbon nitride nanocrystals for efficient hydrogen photosynthesis coupled with furfuryl alcohol oxidation

K/Co co-doped carbon nitride (KCoCN) nanocrystals enable visible-light-driven H₂ evolution (550 μmol g^-1 h^-1) coupled with furfuryl alcohol (FFA) oxidation to furoic acid (FA; 148 μmol and 89% conversion) without sacrificial agents. Mechanism studies reveal that KCoCN accelerates proton reduction to H₂ and promotes FFA oxidation to FA through a hole-driven radical mechanism.