Organic Conjugation of Polymeric Carbon Nitride for Improved Photocatalytic CO2 Conversion and H2 Fixation

The systematic alteration of a carbon nitride unit (CNU) for visible light photocatalytic water splitting is a promising research subject owing to the increasingly serious energy and environmental complications. Herein, the conjugated monomer 3,6‐dibromopyridazine (DBP) is integrated within polymeric carbon nitride (PCN named as CNU = carbon nitride containing urea precursor) via thermal condensation, which is designated as CNU‐DBP. These samples are used for the first time in the photocatalytic conversion of CO2 reduction and hydrogen (H2) evolution through water splitting. Such integration intimidates the electron density, promoting charge transfer separation and elevating the photocatalytic activity of CNU under visible light illumination. The superior sample such as CNU‐DBP9.0 after 4 h of photooxidation generates 65.7 μmol of CO and 17.3 μmol of H2 of the reaction system, emphasizing the highest photocatalytic activity. The H2 evolution rate (HER) for pristine CNU is found as 11.9 μmol h−1, whereas for CNU‐DBP9.0 it is estimated at 178.2 μmol h−1 with 15 times greater activity. This process predicts a significant diversion in the specific area, bandgap, and chemical composition and promotes the efficient separation of photogenerated charge carriers from the ground state to the excited state of CNU, thereby considering it a best candidate for the photoreduction of CO2 source and water splitting into H2.