Activation of Cadmium–Imidazole Buffering Coordination Polymer by Sulfur-Doping for the Enhancement of Photocatalytic Degradation of Cationic and Anionic Dyes Under Visible Light

Abstract

The buffering Cadmium–Imidazole Coordination Polymer (Cd–Im-CP) was synthesized hydrothermally from cadmium chloride and imidazole at 70 °C and then was subjected to doping- by the non-metal sulfur using Na2S solution as a novel modification strategy to produce S–Cd–Im CPs. To investigate doping nature and its effects, Cd–Im CP and S–Cd–Im CPs were characterized applying different analyses techniques, FTIR, Raman, PXRD, SEM/EDX, TGA, and UV–Vis DRS analyses. Characterizations showed the successful chemical doping of sulfur. The inclusion of sulfur within chemical CP structure caused narrowing of material’s bandgap from 4.55 and 3.4 eV to 4.25 and 2.35 eV for S–Cd–Im CPs allowing it for photoresponse towards Visible-light. Both Cd–Im CP and S–Cd–Im CPs were applied for photocatalytic degradation of the selected dyes methylene blue (MB),and methyl orange (MO) employing visible and UV irradiations considering three different initial pH levels to investigate the consequence of sulfur doping. After eliminating the photolysis effect, the best degradation by S–Cd–Im CPs was recorded for MB at initial pH 4 being 13 fold that is for Cd–Im CP. The highest apparent turnover frequencies are 1.2 × 10−3 h−1 for MB at initial pH 10 and 1.03 × 10−4 h−1 for MO at initial pH 4 are given by 10S–Cd–IM CP under Visible-light. Generally, S–Cd–Im CPs remarkably improved photocatalysis degradation of both the dyes for all initial pH levels under Visible-light.