Chapter 1: Covalent organic frameworks (COFs) are the new classes of extended structures formed by the reticular chemistry, which links molecular building units with strong and directional covalent bonds to afford crystalline materials. Reticular design has made it possible to predict crystal structures accurately, to tune chemical composition, to incorporate various functionalities onto the structure’s backbone, and as a result, to fine-adjusst the properties of covalent organic frameworks beeyond those of any other material class. Along with the reticular design, the exceptional porosity and tunable pore size, post-synthetic modification of the interior pores, facile characterization by X-ray diffraction, and straightforward synthesis all indicate that COFs could be exploited in various applications, such as gas storage and separation, catalysis, optoelectronics, and biomedical applications.

Chapter 2: Two entangled 2D square COFs have been synthesized from 4,4',4'',4'''-(9,9'-spirobi[fluorene]-2,2',7,7'-tetrayl)-tetrabenzaldehhyde (SFTB) and p-phenylenediamine (PPA) and benzidine (BZD) to form COF-38, [(SFTB)(PPA)2]imine and its isoreticular form COF-39, [(SFTB)(BZD)2]imine. We also report the single crystal electron diffraction structure of COF-39 and find that it is composed of mutually entangled 2D square nets (sql). These COFs represent the first examples of entangled 2D COF structures, which as we illustrate were made possible by our strategy of using the distorted tetrahedral SFTB building unit. SFTB overcomes the propensity of 2D COFs to stack through π-π stacking and allows for entanglements to form. This work adds significantly to the design principles of COFs.

Chapter 3: A 3D COF, COF-725 was synthesized by imine condensation reactions between an aldehyde-functionalized copper(I)-bisphenanthroline diphenylphosphinate, Cu(PDB)2P, and 5,10,15,20-tetrakis(4-aminophenyl)-21H,23H-porphine, TAPP. Consistent with current results obtained from Powder X-ray Diffraction (PXRD) and simulation, the structure of COF-725 is assigned as exhibiting the pts topology in the Orthorhombic C222 space group. Structurally speaking, this is a 3D COF with interlocked 1D corner-sharing ladders. Within the structure, the positions of the formyl groups approximate a tetrahedron, acting as a point of registry at regular intervals. The TAPP groups extend the 1D ladders in two directions that interlock at these tetrahedral corners. The synthesized COF contains porphyrin motifs that are isolated from possible π-π stacking and are spatially organized in the frameworks. This work highlights the rational design of predictable, extended covalent 3D structures using the principles of reticular chemistry. Chapter 4: The synthesis of a neutral organic linker for woven COF synthesis. This chapter will mainly focus on the efforts spent on synthesizing the neutral organic linkers and the crystallization process of COF-53-Si. This chapter detailed elucidated the process by which the synthesis scheme of the first neutral organic linker SSFTB for woven COFs was developed and the difficulties encountered during the synthesis. Furthermore, extra efforts were made to obtain highly crystalline COF-53-Si because of the low solubility of SSFTB. The basic logic behind how to improve the reaction conditions to make materials that crystallize better was also included in this chapter. Chapter 5: COF-53-Si was synthesized through the combination of SSFTB and rectangular building units, 1,3,6,8-tetrakis(4-aminophenyl)pyrene (TAPP). Characterizations including PXRD, FT-IR, solid-state NMR, ICP, SEM, SEM-EDS, HRTEM, structure modeling, and isotherm will be explored to demonstrate the properties of COF-53-Si. Furthermore, the successful removal of silicon atoms with the existence of TBAF transformed COF-53-Si into COF-53, which was revealed by SEM-EDS and FT-IR spectrum.