In this contribution, a single pot approach was employed to synthesize nanoscale BiVO4/BiOX/Pd, where the halogen was varied over Cl, Br, and I. These materials were used to study the effect of the halide identity in the BiOX nanoplate component for its ability to modulate/maximize the photocatalytic properties of the materials. Once the nanomaterials were fully characterized via a suite of approaches, their reactivity for the degradation of rhodamine B, a model pollutant, was examined. All of the materials demonstrated high photocatalytic rates, reaching completion in <10 min in most cases. The results demonstrated that the BiVO4/BiOCl/Pd and BiVO4/BiOBr/Pd have significantly enhanced reactivity compared to the BiVO4/BiOI/Pd structures. Further studies using the BiVO4/BiOBr/Pd in the degradation of rhodamine B in natural water samples indicated that the materials retained their reactivity, demonstrating their potential use in environmental systems.

We report the preparation of nanostructured ACOF-1@BiOBr with a hierarchical core−shell architecture and demonstrate its performance in the light-driven degradation of organic contaminants. The hierarchical core−shell photocatalyst was prepared using a facile solvothermal method that involves the formation of a BiOBr shell that encapsulates an azine-based covalent organic framework (ACOF-1) sphere. The ACOF-1@BiOBr hierarchical core−shell system manifested enhanced performance over the bare ACOF-1 or BiOBr in the photocatalytic degradation of different organic dyes employed in this study. Such an enhancement can be ascribed to the synergy between ACOF-1 and BiOBr, where the band gap alignment between ACOF-1 and BiOBr forms a Type-II heterostructure. In such a heterostructure, the movement of the photogenerated charge carriers can lower the recombination rate of the produced e − /h+ pairs and, hence, enhance the photocatalytic performance. The rate constants for photocatalytic degradation of the tested dyes were correlated to the surface interaction between the photocatalyst and the dyes. The data revealed that the generation of superoxide radicals was enhanced by the ACOF-1@BiOBr system, which demonstrates the significance of the multicomponent tandem photocatalyst. The hierarchical core−shell ACOF-1@BiOBr presents a paradigm shift in the development of covalent organic frameworks, especially in the field of photocatalysis.

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.

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