Naphthalene Monoanhydride and Perylene Composites for Efficient Photocatalytic Hydrogen Evolution and Metal-Free Heterogeneous Oxidative Amidation

This study explores the synthesis of two visible light active organic chromophore-based composites using naphthalene monoanhydride ( Np ) and 1,7-dibromoperylene monoanhydride diester ( PMDE ). These chromophores feature favorable optical and electronic properties and polyaromatic skeletons with anhydride functionalities that facilitate π–π interactions between the chromophore and polymeric carbon nitride ( CN ) or covalent connections of chromophores with NH 2 groups of CN . Accordingly, heterogeneous chromophore- CN composite photocatalysts namely, Np/ CN (c) and PMDE/ CN (c) were prepared by adopting in situ calcination (c) and composites Np/ CN (a) and PMDE/ CN (a) were prepared by ex situ physical adsorption (a) methods. In situ prepared Np/ CN (c) and PMDE/ CN (c) composites exhibited H 2 evolution rates (HER) of 1069 and 705 μmol h –1 g –1, respectively, which are significantly higher than ex situ Np/ CN (a) and PMDE/ CN (a) composites with HER of 465 and 252 μmol h –1 g –1, respectively. These rates are 10, 7, 4.8, and 2.5 times higher than the bulk- CN, indicating the potential of these composites for efficient photocatalytic H 2 evolution. Surface area normalized HER enhancements were 3.8, 5.3, 6.6, and 4.2 times higher for Np/ CN (c), PMDE/ CN (c), Np/ CN (a), and PMDE/ CN (a) respectively compared to bulk- CN . These composite photocatalysts exhibited excellent stabilities under prolonged photoirradiation, with H 2 evolution consistently increasing with the light exposure time. Additionally, these metal-free heterogeneous composites demonstrated efficient photocatalytic activities towards oxidative amidation of aromatic aldehydes, with up to 80% product yields, establishing the prospects of combining homogeneous and heterogeneous entities in a metal-free active material in solar energy harvesting.