Polymerization methods that provide linear or branched macromolecules with outstanding functional group tolerance and molecular weight control are well studied. In contrast, polymerization strategies that yield two-dimensional (2D) periodic structures remain in their infancy (Chapter 1). Two-dimensional covalent organic frameworks (COFs) are polymer networks that organize molecular building blocks into well-defined porous, layered structures linked by covalent bonds. These materials are usually synthesized as insoluble and unprocessable powders, limiting their utility in applications such as organic optoelectronics. This dissertation describes efforts to overcome the challenges associated with this powder morphology. Initially, COF films were prepared using single-layer graphene (SLG) as a substrate (Chapter 2) and these conditions generalized to a family of 2D COFs with tunable pore size (Chapter 3). Synthetic conditions were developed that provide access to patterned COFs (Chapter 4). COF films that incorporate semiconductors may serve as important precursors for organic optoelectronics. As proof-of-concept, organic photovoltaics fabricated using a variety of COF active-layers were fabricated and characterized (Chapter 5). These results provide a blueprint for incorporating COFs as materials in organic optoelectronic devices. iii