Microporous metal imidazolates [M(Im)₂] have drawn intense attention in recent years as a wide variety of metal coordination polymers which can be functionally applied for separation technology. Due to the strong metal-nitrogen bonds between the metal centers and organic imidazolate ligands, their chemical stability is particularly high and it also leads to exceptional framework thermal stability of 300℃-500℃. They are also of interest as direct topological analogues of silica SiO₂.

Chapter One surveys the background to successful design and preparation of ZIFs and their potential application such as gas storage and separation. In Chapter Two, ZIF analogues of quartz based on [M(2-EtIm)₂] M = Zn, Co and Cd were investigated by studying their synthesis, structures and solid-state...[ Read more ]

Microporous metal imidazolates [M(Im)₂] have drawn intense attention in recent years as a wide variety of metal coordination polymers which can be functionally applied for separation technology. Due to the strong metal-nitrogen bonds between the metal centers and organic imidazolate ligands, their chemical stability is particularly high and it also leads to exceptional framework thermal stability of 300℃-500℃. They are also of interest as direct topological analogues of silica SiO₂.

Chapter One surveys the background to successful design and preparation of ZIFs and their potential application such as gas storage and separation. In Chapter Two, ZIF analogues of quartz based on [M(2-EtIm)₂] M = Zn, Co and Cd were investigated by studying their synthesis, structures and solid-state phase transitions from low-quartz to high quartz. The phase purity, size and singularity of crystals were optimized by varying solvents and modifying solvothermal conditions, with mixed acetomitrile:water being favourable for growth. Study of mixed-metal systems for Zn-Cd and Co-Cd gave single phase solid solutions with preferential incorporation of Zn and Co over Cd. Phase transition temperatures varied between 300-400℃ and were higher for Cd-rich phases. An entropic model to explain this phase-transition behavior is proposed, whereby the high quartz structure offers rotational freedom to the pendant 2-Et groups.

Chapter Three explores high throughput screening of solvothermal conditions using 3D printed vessels. 3D printing is recently developing to be a novel technology for solvothermal synthesis and crystallization of ZIFs. Various thermoplastics are applicable for the manufacture of reaction vessels. Hydrothermal and solvothermal syntheses are examined with these 3D printed vessels, which can replace traditional Teflon cup, and some values and limitation of this technology are discussed.

Finally Chapter Four focuses on mixed 2-methylimidazole and 2-ethylimidazole ligand solid solutions for the quartz-like phases. Interestingly at around 50:50 ratio a new phase type with quartz topology but doubled c-axis is found for Zn, Co and Cd. The space group is found to be P6₅ and P6₅22 for Zn and Cd respectively. These frameworks are more open than low quartz analogues from purely [M(2-EtIm)₂] despite being formed preferentially at higher temperature. Once more this may be explained by an entropic preference for this modified phase allowing greater ethyl group freedom. In addition to double-quartz frameworks some novel ZIFs with Ice-II and Ice-IV topologies were discovered, along with a new 2-MeImH template open framework incorporating imidazole guests which warrants further study of its stability and sorption/desorption properties.