The work presented here focuses on understanding the complex structural phenomena inside metal–organic frameworks (MOFs), zeolitic imidazolate frameworks (ZIFs), and covalent organic frameworks (COFs) by single-crystal X-ray diffraction (SXRD). These materials feature high porosity inside crystal structures, making spaces for the displacements and motions of the framework that are rarely observed in conventional crystals formed by close packing of molecules. While most studies solely rely on SXRD to obtain the skeleton of the structures, recent advances in the crystallographic analyses of reticular materials highlight the importance of rigorous interpretation of the disorders and how the observed static disorders might be associated with dynamics. Chapters 2 and 3 describe a framework-assisted crystal structure determination method for complex small molecules, the coordinative alignment method. Guests were incorporated and covalently attached into MOF-520, providing a platform to understand the behaviors of the guests when residing in a void space. Chapter 2 analyzes the stereoselectivity of the method originated from asymmetric coordination bond, which explains why the method can prevent a primary source of disorder that often interferes structural determination of guests. The thorough look at the solvent-induced guest disorder in Chapter 3 provides an insight into solvent-guest interactions that generally exist in porous crystals, and additionally introduces a method for improving the quality of structural solutions by solvent removal. Chapter 4 reports a correction to a previously reported ZIF structure (ZIF-90) after considering merohedral twinning. Rigorous crystallographic studies revealed the origin of merohedral twinning and associated it with a displacive phase transition at elevated temperatures, introducing a new facet to the forms of disorders in ZIFs and an unprecedented cause of displacive phase transition among any other materials. Finally, Chapter 5 describes the design and synthesis of a woven COF, which by design will transfer to a structure of interlocking 2D rings upon post-synthetic demetallation. It aims at a material at the boundary of crystalline and non-crystalline and thus challenging the boundary of crystallographic characterizations
