Increased catalytic activity through ZnMo7O24/g-C3N4 heterostructured assemblies for greener indole condensation reaction at room temperature

Abstract

As an economical conjugated polymer, graphitic carbon nitride (g-C3N4) has recently attracted much attention due to its exciting chemical and thermal stability and easy availability. Herein, we constructed a metal-coordinated graphitic carbon nitride (M–g-C3N4) catalyst through simple impregnation and calcination methods and used it as a new heterogeneous catalyst for the efficient synthesis of bis (indolyl) methanes and trisindolines under mild conditions. This reaction is performed efficiently in water as an environmentally friendly solvent at ambient conditions. The ZnMo7O24/g-C3N4 nanocomposite was synthesized by a simple method by immobilizing Mo7O24(NH4)6·4H2O and ZnCl2 on the surface of g-C3N4 under hydrothermal conditions. It was characterized by FT-IR, EDS, and electronic scanning microscopy (SEM). The metal doping of Mo and Zn on the surface of graphitic carbon nitride leads to the formation of a green catalyst that gives good to excellent yields of products in short reaction times with an easy working procedure. In addition, the ZnMo7O24/g-C3N4 catalyst could be reused at least five runs without apparent loss of efficiency.

The Importance of Precise Reaction Condition Control for the Comparison of Photocatalyst Materials on the Example of Hydrogen Peroxide Formation over Polymeric Carbon Nitrides

“…[32] However, since this photocatalyst has a low photoconversion efficiency, attempts were made to improve it by means of doping, [33][34] band gap modification, [35][36] co-catalyst loading [37][38] and hybridization with other catalysts. [39][40] Still, for H 2 O 2 , high conversion efficiencies were observed for PCN, where oxygen reacts in a 2electron transfer to form hydrogen peroxide while suppressing the formation of the superoxo radical. [41] Another way to improve the photoefficiency with pure carbon nitride is to create an amine-rich mesoporous surface.…”

“…Moreover, the potentials in the conduction band (CB) and valence band (VB) (E CB =−1.3 V NHE and E VB =1.4 V NHE at pH 7) are thermodynamically suitable for various reactions such as oxygen reduction reaction (ORR), organic pollutant degradation, water splitting and partial oxidation [32] . However, since this photocatalyst has a low photoconversion efficiency, attempts were made to improve it by means of doping, [33–34] band gap modification, [35–36] co‐catalyst loading [37–38] and hybridization with other catalysts [39–40] . Still, for H 2 O 2 , high conversion efficiencies were observed for PCN, where oxygen reacts in a 2‐electron transfer to form hydrogen peroxide while suppressing the formation of the superoxo radical [41] .…”