SYNTHESIS OF METAL-ORGANIC FRAMEWORKS THROUGH GREEN SYNTHETIC PATHWAYS AND THEIR APPLICATIONS

Abstract

Metal-organic framework complexes in general and multi metal-citrate complexes in particular have been synthesized through green route. Hydrothermal method adopted in present research is decorated with features; a simple one pot synthesis, cost effectiveness & easy to scale up for commercial production. Efficient synthesis conditions like mild temperature & shorter duration further rules out possibility of forming byproducts which may cause damage to environment. The synthesis is environmental benign, as it eliminates use & recovery of harmful organic solvents namely N, N-dimethyl formamide & N, N- diethyl formamide, used by researchers in synthesis of metal-organic framework complexes. Multiple metal ions introduced in their frameworks to exploit unique coordination properties of different metals ions. Multi metalcitrate complexes have also been synthesized using lime juice, squeezed from fresh fruit & strained, thereby reducing time & cost involved in extraction of citric acid commercially. These complexes are bluish green well defined crystalline solids having cubic geometry with a layered structure supported by a strong network of hydrogen bonds formed by ─OH of coordinated water lying between layers. They have been characterized by Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Energy Dispersive Spectroscopy, UV-Vis spectroscopy & Powder X- Ray diffraction techniques. Stability of complexes has been established by Thermogravimetric analysis. Complexes exhibit mesoporous character & narrow pore size distribution as demonstrated by BJH & DFT models. Owing to good adsorption properties & mesoporous nature, these complexes exhibit exorbitant adsorption affinity for large molecules of dyes & can be used as scavengers for dye stuff removal from industrial waste discharge to replace high cost carbon adsorbents & prevent water pollution with resultant toxic, carcinogenic & mutagenic effects of dye stuff on living beings. Multi metalcitrate complexes serve as promising luminescent probe for sensing & recognition of NH4+, Fe(CN)6 4-, I ¯, CrO42 & Cr2O7 2- ions through a simple & straight forward method involving conspicuous visual display of color change upon introduction of guest ions in their framework. They may be explored for applications in gas adsorption & separation and sensing, capture & catalytic degradation of harmful gases. Being fluorescent they have great potential in bio medical field for drug storage, drug delivery, medical imaging & biological sensors which require water soluble nanocrystalline fluorescent materials.