Cu₂O Cubes Decorated with Azine-Based Covalent Organic Framework Spheres and Pd Nanoparticles as Tandem Photocatalyst for Light-Driven Degradation of Chlorinated Biphenyls

Abstract

Covalent organic frameworks (COFs) are promising candidates for heterogeneous photocatalytic reactions, though highly efficacious semiconductor–metal assemblies are often required to foster their photocatalytic performance. Herein, we report an efficient photocatalytic hybrid material that involves loading azine-based COF spheres onto Cu2O cubes and decorating them with palladium nanoparticles. The photocatalytic performance of the material was studied via the light-driven degradation of chlorinated biphenyls. The Cu2O-ACOF-1@Pd system demonstrated an outstanding performance over the bare Cu2O or ACOF-1, which can be attributed to the synergistic effect induced by the multicomponent tandem photocatalyst. It is shown that for monochlorinated biphenyls, the congener with a chlorine atom in the para position is more vulnerable to degradation than its meta and ortho counterparts because of electronic effects and being less sterically hindered. Moreover, the presence of a chlorine atom in the para position as an electron donor increases the conjugation between the phenyl rings, which in turn increases the driving force for planarity that facilitates the removal of the chlorine atom. This trend could be attributed to the reactivity of superoxide radicals toward the different congeners of monochlorinated biphenyls. The data revealed that nucleophilic substitution occurring at the para position is characterized by the lowest Gibbs free energy, while that occurring at the ortho position is characterized by the highest Gibbs free energy.

Cu2S@Bi2S3 Double-Shelled Hollow Cages as a Nanocatalyst with Substantial Activity in Peroxymonosulfate Activation for Atrazine Degradation

“…Cu 2 O cubes were prepared using a procedure described in our previous protocols. − Selected amounts of the obtained Cu 2 O cubes were ultrasonically dispersed in 100 mL of an ethylene glycol–H 2 O (90:10 v/v) solution containing 0.32 g of BiNO 3 ·5H 2 O. Two different loadings of BiOBr with bismuth contents of 22 and 44 wt % were prepared by controlling the amount of the Cu 2 O template.…”

Hierarchical Core–Shell ACOF-1@BiOBr as an Efficient Photocatalyst for the Degradation of Emerging Organic Contaminants

“…ACOF-1 was prepared using an ultrasonic preparation method. 23 Typically, 240 mg of 1,3,5-triformylbenzene was ultrasonically dispersed in 8 mL of dioxane and 800 μL of acetic acid (6 M). The glass vial was sealed and flushed with ultrapure nitrogen for 10 min to expel oxygen from the reaction medium.…”

“…26 The N 1s spectrum (Figure 4c) shows a peak at 399.1 eV that is assigned to the azine linkage CN of ACOF-1, and the small peak at 400.3 eV is ascribed to the C−N bond. 23,27,28 On the other hand, the peak observed at 403.3 eV is attributed to the πexcitation of the CN bond. 29 The Bi 4f spectrum shows two peaks at 159.5 and 165 eV that are assigned to Bi 4f 7/2 and Bi 4f 5/2 , respectively.…”

Covalent organic framework supported palladium catalysts

“…This catalyst showed outstanding photocatalytic activity for the degradation of polychlorinated biphenyls (PCBs). 74…”