DESIGN AND FUNCTIONS OF SHEET-SHAPED MACROMOLECULES

Covalent organic frameworks (COFs) are porous and crystalline polymer with a well defined and predictable network of building blocks. Compared with inorganic porous materials, COFs are unique in that they are made from lighter elements, are robust towards air and organic solvents, and have tunable skeletons. From a synthetic viewpoint, COFs are attractive motifs since they allow total control over structural parameters, including composition and porosity. Most studies up to date have focused on the development of synthetic methodologies with the aim of optimizing pore size and surface area. In contrast, the functions of COFs, except for gas storage, have not yet been well explored. This motivated me to explore the possibility of constructing functional COFs with novel properties by utilizing highly ordered π-conjugation systems. This thesis consists of the design, synthesis and function exploration of novel sheet-shaped macromolecules and their covalent organic frameworks, with an emphasis on the development of π-electronic organic frameworks.(1) A Belt-Shaped, Blue Luminescent, and Semiconducting Covalent Organic Framework In the first part, the author reported the first example of a luminescent and semiconducting COF, which adopts a belt shape and consists of pyrene and triphenylene functionalities alternatively linked in a mesoporous hexagonal skeleton. A new family of covalent organic framework based on π electron system was synthesized by condensation polymerization with triphenylene and pyrene derivatives as monomers (TP-COF).TP-COF adopts belt morphology with thickness of about 100 nm, width of about 300 nm, and length of micrometers. When triphenylene and pyrene unit were selectively excited by ultraviolet and visible light, TP-COF displays strong blue fluorescence at 474 nm, as a result of an efficient energy transfer between two units. This result demonstrates that TP-COF collects photons of a wide range covering from ultraviolet to the visible regions and converts them to blue emission efficiently.In addition, due to the ultimate π stacking of large π-conjugated components, TP-COF is electrically semiconducting. The electric current can be repetitively on/off switched without any deterioration. Upon doping with iodine, the electric current was increased remarkably, which suggests that TP-COF is p-type semiconductor.(2) A Poly(pyrene)-Based Blue Luminescent, Semiconducting and Photoconductive Covalent Organic FrameworkUp to date, two typical architectures i.e., boronic ester and triazine, have been reported as joint points for covalent connection of multiple building blocks into sheet-shaped macromolecules and COFs. Among them co-condensation of boronic acid with phenol derivatives has been demonstrated utility in the synthesis of various boronic ester-based COFs. On the other hand self-condensation of boronic acid derivatives has been limited to one example, i.e., benzene 2,7-diboronic acid, which, however, leads to a COF with staggered alignment of 2D polymer sheet. In this part, the author demonstrated the synthesis of a new π-electronic COF based on self-condensation of pyrene diboronic acid under solvothermal condition (PPy-COF). FE SEM shows that PPy-COF assumes micrometer-sized cubic shape, while no any other morphology such as belt, fiber, sphere, or rod are present, indicating high phase uniformity. PPy-COF exhibits high blue luminescence at 484 nm upon excitation at pyrene unit (414 nm). PPy-COF is electrically semiconducting and shows p-type character. Moreover, the ultimate alignment of 2D poly(pyrene) sheets in a perfectly eclipsed fashion allows a large charge carrier mobility. Significantly depolarized fluorescence anisotropy suggests that the excitation energy is not localized but migrate over the framework. PPy-COF is semiconducting and enables an on/off switch of electric current at room temperature. Moreover, PPy-COF is photoconductive with a quick response to light irradiation and a large on/off ratio.(3) Anthracene-Based Photo-Addressable Covalent Organic Framework In this part, the author disclosed the design and synthesis of a new type of COF based on co-condensation of benzene triboronic acid and 2,3,6,7-tetrahydroxyanthracene under solvothermal or reflux conditions (An-COF). An-COF consists of benzene and anthracene components alternatively linked in a mesoporous hexagonal skeleton. FE SEM reveals that An-COF adopts well-defined micrometer-scaled 2D sheet shape. The ultimate alignment of An-COF sheets in a perfectly eclipsed fashion allows photoinduced dimerization and reversible monomerization of anthracence units in An-COF. Such a photo-addressable COF may find applications in tuning luminescence and high-density data storage. Moreover, An-COF is electrically semiconducting and highly luminescent.Exploration of functional COFs is a subject that has a high probability to lead to the development of new materials. In summary, the author has developed a series of novel π-electronic sheet-shaped macromolecules and covalent organic frameworks. Based on the chemistry of boronic ester reaction, the author designed and synthesized a series of new π-electronic monomers and succeeded in the construction of π-electronic sheet-shaped macromolecules. By using different monomers and polymerization methods, 1D belt-shaped (TP-COF), 2D sheet-like (An-COF) and 3D cubic (PPy-COF) COFs were created. These π -electronic organic frameworks show unique photo and electric functions that clearly originate from their highly ordered structure and thus open a new way to polymeric optoelectronics and electronics