Through Space Sigma Donation π Acceptor Assisted Photocatalytic Degradation of Ciprofloxacin on TCPP Supported g‐C₃N₄

Abstract

Photocatalysis on pristine g-C 3 N 4 (CN) often suffers from fast recombination of photogenerated electrons and holes. Herein, we demonstrate the superior photocatalytic performance of free base tetrakis(4-carboxyphenyl) porphyrin (TCPP) -g-C 3 N 4 (CN/TCPP) hybrids synthesised by a facile ultrasound aided impregnation. Structural and morphological characterisation confirmed the successful formation of the hybrid via noncovalent π-π stacking. Optical/electrochemical characterisation, as well as DFT study, designates the shifting of the optical absorption edge to visible range along with inhibition of carrier recombination through enhanced charge transfer. The CN/ TCPP hybrids exhibited superior performance towards the degradation of persistent antibiotic ciprofloxacin under visible irradiation signifying its enhanced visible light sensitivity. The enhanced photocatalytic activity of CN/TCPP is ascribed to the charge transfer by through-space conjugation by migration of electrons and holes in opposite directions, which minimises the possibility of electron-hole recombination. From the LCMS data, scavenging studies, and first principles DFT analysis, the photodegradation of CIP is proposed to proceed via the destruction of the piperazine ring initiated mainly through the electrophilic attack by the holes.

Heterojunction Engineering of g‐C3N4 with CuO for Enhanced Photocatalytic and Photoelectrochemical Performance

“…The absence of distinctive peaks corresponding to CuO or any shift in the inherent peaks of g‐C 3 N 4 may be due to the relatively low content and fine dispersion of CuO on 2D layers. [ 22 ] The surface functionalities of g‐C 3 N 4 and g‐C 3 N 4 /CuO hybrid systems were analyzed by FTIR spectroscopy (Figure 1c). The broad peak observed in the range 3000–3500 cm −1 could be ascribed to N–H stretching vibration of terminal amino groups and may also have the contribution of O–H from adsorbed moisture.…”

“…Synthesis of Graphitic Carbon Nitride (g-C 3 N 4 ): g-C 3 N 4 was synthesized by solid-state thermal polymerization method using a mixture of urea and thiourea as precursors, as reported earlier. [22] Typically, a 1:1 mixture of urea and thiourea was thoroughly mixed in a covered silica crucible and subjected to heat treatment in a muffle furnace at 550 °C for 1 h. After cooling down to room temperature, pale yellow residue of graphitic carbon nitride was collected and ground into fine powder.…”

“…Due to the favorable band alignment, the electrons from the CB of CuO can undergo injection into the VB of g-C 3 N 4 and subsequently get promoted to the CB of g-C 3 N 4 , thereby completing the Z scheme. [22,49] The electrons accumulated at the CB of g-C 3 N 4 will induce the formation of O 2 À . Since the VB edge of g-C 3 N 4 is less positive than the water oxidation potential, it seems highly improbable that the generation of hydroxyl radicals is mediated by the accumulated holes in the VB.…”

“…[13][14][15] Further, its utility for CO 2 reduction has also been reported. [16][17][18] Several strategies including defect/vacancy generation, [19] exfoliation, [20] heteroatom doping, [21] dye sensitization, [22,23] cocatalyst loading, [24] heterojunction formation, [25] etc. have been put forth to mitigate the insufficient light absorption, fast recombination of photogenerated electrons and holes, and low surface area which curb the PC performance of g-C 3 N 4 .…”

Flower‐Like Ag6Si2O7/Bi12O17Cl2 p‐n Heterojunctions: Enhanced Photocatalytic Activity and Mechanistic Insight**

“…To elucidate the activity enhancement mechanism of Ag 6 Si 2 O 7 /Bi 12 O 17 Cl 2 -2 catalysts, the PL spectra, photocurrent, EIS analysis and N 2 adsorption-desorption isotherms are used to indirectly reflect the separation and recombination of photogenerated electron-hole pairs (Figure 9). [39] Figure 9A shows PL spectra at excitation of 325 nm light source. -2 significantly enhances the separation of light-induced carrier.…”