Comparative analysis of solvent effects on ZIF-8 features via solvothermal synthesis for enhanced drug delivery applications

Abstract

ZIF-8 is a member of the zeolitic imidazolate framework (ZIF) family, which falls within the broader category of metal-organic frameworks (MOFs). MOFs are a class of crystalline materials composed of metal ions or clusters coordinated with organic ligands. ZIFs are distinguished by their zeolite-like characteristics, resembling the structure and properties of zeolites, but with the added flexibility of incorporating various metal ions. The remarkable features of these nanoparticles are persistent porosity, outstanding thermal and chemical stability, and uniform pore size. ZIF-8, specifically, is one of the most extensively studied ZIFs. It is composed of zinc ions (Zn2+) coordinated with 2-methyl imidazolate (MeIm) ligands. The resulting framework possesses a three-dimensional porous structure with regular and uniform nanosized pores. This structure enables ZIF-8 to exhibit exceptional properties, making it highly attractive for a wide range of applications. This thesis aims to investigate the synthesizing of zeolitic imidazolate framework-8 (ZIF-8) using various solvents, explicitly focusing on the effects of DI water, methanol, and butanol. ZIF-8 is a prominent metal-organic framework (MOF) with versatile applications in gas separation, catalysis, and drug delivery. The choice of solvent during synthesis significantly influences the structure, morphology, and performance of ZIF-8 to make an ideal choice for each application and usage. The study commences with a review of ZIF-8's structural characteristics, solvothermal synthesis method, and the role of solvents in MOF formation. The thesis then outlines a systematic experimental design to evaluate the influence of DI water, methanol, and butanol on features of ZIF-8. These solvents were chosen due to their diverse properties, including polarity and molecular structure. The thesis highlights the solvent-dependent variations in these properties, shedding light on the specific effects of DI water, methanol, and butanol on ZIF-8 synthesis. The experimental synthesis process explores the impact of changing solvents on the features of ZIF-8. This analysis includes the evaluation of crystal size distribution, morphology, and pore characteristics for each solvent system. The synthesis is conducted under constant and identical conditions, including temperature, reaction time, reactant concentrations, and solvent-to-reactant ratio. Each synthesis condition is carefully monitored and characterized using techniques such as X-ray diffraction (XRD), thermogravimetric analysis (TGA), and nitrogen adsorption-desorption measurements (BET). These analytical methods provide valuable insights into the structural, thermal, and adsorption properties of the synthesized ZIF-8 samples. The obtained results are analyzed in terms of crystallinity demonstrating a very favorable crystallinity of 90-97%, surface area, porosity, and stability of the synthesized ZIF-8 samples. The observed promising crystallinity of 90-97% in the synthesized ZIF-8 nanoparticles further highlights their potential for various applications. Furthermore, the thesis delves into the implications of solvent selection on the performance of ZIF-8 in the application of drug delivery systems. Specifically, drug delivery experiments are conducted to evaluate the influence of DI water, methanol, and butanol on the adsorption capacities and selectivity of ZIF-8 in terms of loading and release of a model drug. Allantoin is chosen as the model drug due to its relevant features in drug delivery applications. The results obtained from these experiments offer valuable insights into the suitability of ZIF-8 for the loading and release of this specific drug, contributing to the understanding of its potential in drug delivery systems. In this investigation, post-synthesis loading and releasing drug (allantoin) were investigated at pH 6.4 since it is the pH of wound fluids, by using a UV-visible spectrophotometer. The results show that zif-8 has potential to be used in drug delivery systems.