Room Temperature Synthesis and Characterizations of ZIF-8 Formation at Water-Fatty Alcohols Interface

Abstract

In this study, Zn based ZIF-8 metal-organic framework were successfully synthesized in a green synthesis approach eliminating hazardous solvents and the need to use surfactant. In this method, the syntheses were done at room temperature followed by a simple hydrothermal method using palm oil derived fatty alcohols (PODFA) with 12 carbon chain in various solvents. The effect of several co-solvents on the formation of ZIF-8 materials and on morphology were investigated. The peak positions agreed well with the simulated ZIF-8. However, as the co-solvents became more polar the (011) peak shifted to a higher 2θ value suggesting that the interplanar d-spacing were reduced. The addition of fatty alcohols promoted the formation of MOF-5 and ZIF-8 at the water-fatty alcohols interfaces by viscosity lowering effect similar to those when using commercial surfactants. The mechanism of the formation was suggested to be similar to those at water-alcohol insoluble monolayer interfaces at the liquid-gas interaction. As the polarity of solvents increased, the miscibility of Zn2+ ions and deprotonated methylimidazole linkers were enhanced causing higher interaction with metal ions which resulted in a smaller unit cell. ZIF-8 exhibited elongated rhombic dodecahedron and truncated dodecahedron morphology at less than 100 nm.