Mitigating phytotoxicity of tetracycline by metal-free 8-hydroxyquinoline functionalized carbon nitride photocatalyst.

Photooxidative removal of pharmaceuticals and organic dyes is an effective way to eliminate growing micropollutants. However, photooxidation often results in byproducts as secondary hazardous substances such as phytotoxins. Herein, we found that photooxidation of common antibiotic tetracycline hydrochloride (TCH) over a metal-free 8-hydroxyquinoline (8-HQ) functionalized carbon nitride (CN) photocatalyst significantly reduces the TCH phytotoxic effect. The phytotoxicity test of photocatalytic treated TCH-solution evaluated towards seed growth of Cicer arietinum plant model endowed natural root and shoot growth. This study highlights the conceptual insights in designing of metal-free photocatalyst for environmental remediation.

Potassium Molten Salt-Mediated In Situ Structural Reconstruction of a Carbon Nitride Photocatalyst.

Metal-free polymeric carbon nitride (PCN) materials are at the forefront of photocatalytic applications. Nevertheless, the overall functionality and performance of bulk PCN are limited by rapid charge recombination, high chemical inertness, and inadequate surface-active sites. To address these, here, we employed potassium molten salts (K+X-, where X- is Cl-, Br-, and I-) as a template for the in situ generation of surface reactive sites in thermal pyrolyzed PCN. Theoretical calculations imply that addition of KX salts to PCN-forming monomers causes halogen ions to be doped into C or N sites of PCN with a relative trend of halogen ion doping being Cl < Br < I. The experimental results show that reconstructing C and N sites in PCN develops newer reactive sites that are beneficial for surface catalysis. Interestingly, the photocatalytic H2O2 generation rate of KBr-modified PCN was 199.0 µmol h-1, about three times that of bulk PCN. Owing to the simple and straightforward approach, we expect molten salt-assisted synthesis to have wide exploration in modifying PCN photocatalytic activity.

Accelerating NADH oxidation and hydrogen production with mid-gap states of nitrogen-rich carbon nitride photocatalyst.

Regeneration of electron carriers such as NAD+/NADH is highly desirable and essential for enzymatic conversions. Here, we demonstrate a sustainable strategy for the regeneration of NAD+ as an electron carrier via photon-assisted heterogeneous catalysis. For this, a mid-gap state induced nitrogen-rich polymeric carbon nitride (NPCN) catalyst was synthesized by an additive-assisted thermal copolymerization. Utilizing NPCN as a photocatalyst presented NADH photooxidation efficiency of over 98% and a high hydrogen production rate of 11.18 mmolg-1h-1 with an apparent quantum yield of 9.16% (λ = 420 nm), outperforming other state-of-art metal-free photocatalysts. The experimental and theoretical simulations suggest that mid-gap states in NPCN catalyst are main platform for charge-carrier separation that enhances the overall photocatalytic performance.

Extended π-conjugative n-p type homostructural graphitic carbon nitride for photodegradation and charge-storage applications.

An n-p type homostructural metal-free graphitic carbon nitride (g-C3N4) semiconductor is designed and developed for pollutant abatement and energy storage application. The successful grafting of vibrio-like morphology-based g-C3N4 by 2, 5-Thiophenedicarboxylic acid (TDA) molecule and the development of amide-type linkage substantiated the prosperous uniting of g-C3N4 with organic TDA moiety is demonstrated. An extended π-conjugative TDA grafted g-C3N4 exhibited band gap tunability with broadband optical absorbance in the visible region. Mott-Schottky analysis exhibited the formation of n-p type homostructural property. As a result, obtained TDA grafted g-C3N4 has extended π-conjugation, high surface area and adequate separation of charge carriers. The change in the photocatalytic performance of grafted g-C3N4 is inspected for degradation of acid violet 7 (AV 7) dye under visible light irradiation. The charge storage capacity of grafted g-C3N4 was additionally assessed for supercapacitive behaviour. The charge capacitive studies of grafted g-C3N4 exhibited the areal capacitance of 163.17 mF cm-2 and robust cyclic stability of 1000 cycles with capacity retention of 83%.