Room Temperature Synthesis and Characterizations of Cu-MOF using Natural Polysaccharide as Potential Organic Linker

Abstract

In this study, copper-based metal-organic framework was successfully synthesized using natural polysaccharide, gum Arabic (gA, Acacia Senegal) as potential organic linker by adopting the synthesis method from Misran et al. with some modifications. The copper-based metal-organic framework (Cu-MOF) was obtained from the combination of copper salt, natural polysaccharide, and terephthalic acid (H2BDC) at various ratio. The synthesis process was done with the addition of triethylamine (TEA) as catalyst. X-ray Diffraction (XRD) pattern exhibited the presence of a prominent peak assigned to (200), (400), (511), (731), (773), and (882) crystal plane almost similar to the octahedral copper-based MOF-199. Field Emission Scanning Electron Microscopy (FESEM) shown an agglomeration and flaky particle. Energy Dispersive X-Ray Spectrometry (EDX) shown three main elements exist inside the Cu-MOF which is carbon (C), copper (Cu), and oxygen (O). This study showed the possibility of natural polysaccharide as new, non-toxic, water soluble linker. Thermogravimetric Analysis (TGA) analyses of as-synthesized Cu-MOF exhibited three different weight losses when heated to ca. 600oC. The first mass decrease was due to loss of water content followed by the loss of organic moieties inside the Cu-MOF framework and the last was due to the collapse of MOF’s structure leaving metal oxide as the final residue The Fourier-Transform Infrared Spectroscopy (FTIR) spectra suggested strong absorption band at ca. 900 – 1200 cm-1 attributable to C-O bonding, at ca. 1045 cm-1 attributable to C-H bonding originating from gum Arabic, at ca. 1500 – 1600 cm-1 from the organic linker benzene ring, and at ca. 3200 – 3500 cm-1 from hydrogen bonding. These results suggested that natural polysaccharide of gum Arabic exhibited the possibility to become a new, non-toxic, renewable linker for the MOF materials and played a significant role in metal-organic framework formation.