A novel sustainable metal organic framework as the ultimate aqueous phase sensor for natural hazards: detection of nitrobenzene and F- at the ppb level and rapid and selective adsorption of methylene blue

摘要

Herein, a new cationic Cu(ii)-based porous and water stable metal-organic framework (MOF), [{Cu(bipy)(1.5)(H(2)pdm)}center dot 2NO(3)center dot H2O](n) (Cu-MOF-1), is synthesised via a slow evaporation process using pyridine-2,6-dimethanol (H(2)pdm) and 4,4 '-bipyridine (bipy). The MOF is characterized using Fourier-transform infrared (FTIR) spectroscopy, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), magnetic analysis and single-crystal X-ray diffraction analysis. The structural unit of Cu-MOF-1 consists of two Cu(ii) ions bridged by bipy and supported by H(2)pdm. This material exhibits excellent sensing ability for nitrobenzene (NB) and fluoride ions (F-) in 100% aqueous medium with an ultra-low limit of detection of 0.093 and 1.203 ppb for NB and F-, respectively. The detection of nitro aromatic compounds (NACs) was found to be governed by photo-induced electron transfer (PET) and fluorescence resonance energy transfer (FRET) mechanisms, while vapour pressure played a major role in NB detection, with a high fluorescence quenching of 96.4%. Moreover, the MOF showed high water stability, significant recyclability and microporosity. The MOF was also employed for the adsorption and separation of methylene blue (MB) from a mixture of three dyes (MB, rhodamine-B and methyl orange). At equilibrium, the removal percentage of Cu-MOF-1 for MB was 98.23% and the mechanism of dye adsorption was also explored. Thus, the present MOF was determined to be a sustainable multifunctional material for the aqueous phase sensing of hazardous NB and fluoride ions, as well as an excellent dye adsorbent.