Kinetic Assembly of a Thermally Stable Porous Coordination Network

Abstract

This thesis describes advances in the field of porous coordination network synthesis by kinetic assembly. The kinetic assembly can give interactive sites facing to the pores. This interactive pore makes it possible to develop the kinetic trapping of guest molecules under non-equilibrium condition. Chapter 1 is a brief summary of the conventional identification methods of reaction intermediates and the recent developments regarding structure determination by pore effect. Crystalline solid of porous coordination networks enable to reveal the structure of guest molecules in the pores by X-ray diffraction. In order to trap reactive species, however, it is essential to prepare interactive sites in pores. One of the promising ways to prepare such interactive pores is kinetic control during a self-assembly of coordination networks. This chapter describes introductory aspects of kinetic assembly for synthesis of porous coordination networks. Chapter 2 describes the novel approach to construct kinetically-assembled thermally stable porous coordination network using labile metal cluster; copper(I) iodide (CuI) cluster that shows structural diversity in solution. Thanks to kinetic assembly, the network has interactive pores in the structure and bigger void spaces compared with thermodynamically-assembled one. Chapter 3 demonstrates unique iodine sorption/desorption behavior of networks described in chapter 2. Thanks to interactive pores, kinetically-assembled network shows chemisorption of iodine. However, chemisorbed iodide easily desorbed compared with thermodynamically-assembled one, even though thermodynamically- assembled one shows physisorption of iodine. Chapter 4 presents direct X-ray observation of small sulfur allotropes S2, bent-S3 and cyclo-S3in the networks described in chapter 2. Even though the sulfur allotropes are quite reactive and non-isolable, these allotropes were encapsulated into the networks by direct kinetic trapping of sulfur vapor thanks to interactive pores. This is the first example of the observation of cyclo-S3 which is expected as less stable trisulfur species than bent-S3 by theoretical calculations. Temperature-dependent X-ray diffraction experiments revealed successive reaction of the sulfur allotropes like a snapshot.