The development of general methods for the organization of molecules on technologically relevant materials enables the exploration of properties and functions that are not present in either the molecules or the materials alone. Bottom-up self-assembly of molecules is an especially promising approach for achieving these hybrid molecule–material systems with nanoscale precision. A modular approach to bottom-up self-assembly, where a functional group is attached to a molecular platform which forms ordered monolayers, seeks to expand the applicability of bottom-up self-assembly to a wide-range of molecules by decoupling the formation of ordered structures from the function in these systems. The central hypothesis of this work is that ordered porphyrin monolayers can serve as molecular platforms for modular self-assembly, enabling the incorporation of diverse molecular functionality onto wide array of materials.This work describes the functionalization of materials using ordered porphyrin monolayers utilizing two approaches. The first approach explores the surface chemistry of metalloporphyrins on 2D TMDs. The effect of the metal center in a series of M(OEP) complexes (M = Ni, Zn, H2 and Ga(Cl)), the peripheral substituents, the surface composition, and the deposition conditions on resulting porphyrin monolayers are explored via scanning tunneling microscopy at the solid–liquid interface. Computational chemistry was also utilized to explore the thermodynamics of self- assembly and electronic consequences of the formation of these interfaces. Finally, a modular self- assembly approach is described, where an electroactive ligand (ferrocene) was covalently attached to a five-coordinate gallium porphyrin, demonstrating the organization of a functional molecule on a 2D TMD. The second approach explores using ordered monolayers of porphyrin dimers as a template for the organization of fullerenes. The synthesis of a series of cofacial porphyrin dimers, (Ga(OEP))2(μ-R), is described; the molecular structures and physical properties of these multi- porphyrin systems were investigated. The surface chemistry of these cofacial porphyrin dimers was then explored both as pristine monolayers and as a template to form bicomponent monolayers containing fullerene. The thermodynamics of the supramolecular organization of fullerenes were explored using computational chemistry for both the dimeric porphyrin systems along with a series of monomeric porphyrin systems, Ga(OEP)(R), containing axial fullerene affinity groups leading towards a method for computationally screening candidates for modular self-assembly.