Tailoring Sg-CN with Nickel(II) Atrane for Sustainable Photocatalytic Nitrogen Fixation

The artificial nitrogen fixation under mild conditions is one of the challenging goals for the scientific community. This work demonstrates the reduction of N₂ to ammonia in the presence of a photocatalyst derived by integration of Ni(II) atrane and sulfonated graphitic carbon nitride (Sg-CN). The Ni(II) atrane was prepared from a tripodal ligand (TPL) derived from iminodiacetic acid and styrene oxide and subsequently incorporated into the sheets of sulfonated graphitic carbon nitride (Sg-CN) to form a heterojunction composite, Ni-TPL/Sg-CN. The sequential products, TPL, Ni(II) atrane, and Ni-TPL/Sg-CN were characterized by SCXRD, FTIR, TGA, BET, FESEM, HRTEM, and XPS. Integration of Sg-CN and Ni-TPL lowered the overall band gap of the composite in comparison to the pristine precursors, attributed to the enhanced charge transport and suppressed recombination at the interface. The composite demonstrated efficient photocatalytic activity due to the availability of nitrogen vacancies, producing 241 μmol g^-1 of ammonia from dinitrogen within an hour of exposure to visible light. Also, the apparent quantum efficiency (AQE) was found to be 0.171%. Moreover, the photocatalyst showed reproducible catalytic efficiency up to six consecutive cycles and 24 h of durability without the disintegration of the structural integrity. This work promises a highly efficient approach to nitrogen fixation under mild conditions.