Cu(BDC) as a catalyst for rapid reduction of methyl orange: room temperature synthesis using recycled terephthalic acid

Terephthalic acid was recycled from waste PET bottles with a basic hydrolysis technique and characterized with UV and FTIR spectroscopy. Copper-based metal–organic framework Cu(BDC) was synthesized at room temperature without any additive; two different temperatures were chosen to activate the obtained material. Characterization studies were performed using XRD, N2 physisorption, STEM and EDX. The obtained material was tested as a catalyst for the reduction of methyl orange with NaBH4 in aqueous solutions. Thermal activation at 160 °C proved to be mandatory for catalytic activity; although higher temperature activation did not cause significant enhancement. Rapid dye removal was monitored by continuous photometry at λmax. The results were quite satisfactory (about 85% removal in 5 min); even higher than the published results for precious metal (i.e., Au, Pt and Ag) nanoparticles. In an increased reaction scale, UV–visible spectra and mass spectrum were recorded to help elucidating the possible reaction mechanism. In addition, recycling experiment were performed in 100-ml scale without any kind of re-activation (washing or drying) to show the ability of Cu(BDC) as a stable catalyst for reductive dye removal (and probably similar reactions as well).