A cadmium-imidazole coordination polymer as solid state buffering material: Synthesis, characterization and its use for photocatalytic degradation of ionic dyes

A cadmium-imidazole coordination polymer (Cd-Im CP) was facilely synthesized in ethanol/aqueous solution at low temperature and was characterized using PXRD, FTIR, Raman, SEM/EDX and N2-BET analyses. Structure solution, performed by Reflex module/Materials Studio validated the coordination as [Cd(HIm/Im/OH)]n. Cd-Im CP was examined for its potential use to photocatalytically degrade the cationic dye methylene blue (MB) and the anionic dye methyl orange (MO) under properly selected UV light source (254 ​nm, 24 ​W) at different initial pH. Photocatalytic-degradation experiments revealed similar pH-degradation profile for both dyes where the highest degradation was recorded at nearly neutral pH of and rate constants were 0.0083 and 0.0047 ​min−1 for MB and MO respectively. Degradation analyses elucidate that Cd-Im CP has a buffering effect, a character that strongly impacted the degradation mechanism. Due to limited adsorption of dyes by Cd-Im CP, the proposed mechanism of degradation comprises diffusion of O2•− radicals toward the bulk solution where degradation occurs, meanwhile for basic and acidic conditions dyes’ molecules diffuse toward Cd-Im CP surface where they experience collisional-interaction with O2•− nearby the Stern layer, and thereafter degradation follows known pathway.