Metal–organic frameworks (MOFs) and covalent organic frameworks (COFs) are related classes of porous crystalline materials defined by their ordered structures and accessible void spaces. The outstanding tunability of both materials has led to their recent proliferation and exploration in an impressive array of applications that promise to improve our lives. This dissertation is focused on understanding the self-assembly of these materials to produce them more efficiently and maximize their capabilities, as well as furnish new materials with uncommon capabilities through judicious control of their syntheses. Chapter 1 provides a brief introduction and historical account of both classes of materials and their syntheses, including challenges associated with their production on scale and their continued innovation. Chapter 2 highlights emerging synthetic methods that seek to make large-scale MOF production more practical. Chapter 3 offers an analysis of the adsorption and activation of the potent greenhouse gas nitrous oxide by MOFs containing accessible, coordinatively unsaturated metal centers to determine structure-property trends that drive adsorption strength. Chapter 4 presents another structure-property analysis focused on the impact of certain additives on the crystallinity and porosity of zirconium-based MOFs related to the structures of the additives. Chapter 5 seeks to improve batch syntheses of MOFs by uncovering fundamental insights that control the self-assembly of related crystalline phases under high-concentration conditions. These insights also enable the production of many new frameworks, some demonstrating remarkable solid-state photoluminescence. Finally, chapter 6 describes for the first time, the judicious optimization of N-heterocyclic carbene dimerization, a carbon-carbon double bond-forming reaction, for COF synthesis. This unexplored COF linkage imparts the product, CORN-COF-1, with unprecedented redox properties among COFs, leading to the stabilization of reactive radical species and broadening the scope of reactions that COFs are capable of.