Metal–organic frameworks (MOFs) possess tuneable properties and a variety of important applications in the areas of catalysis, adsorption, gas storage, and separation, among others. Herein, recent computational studies by density functional theory (DFT) applied for simulations of MOF structure and complex architecture determination, prediction of properties, and computational characterization, including large-scale screening and geometrical properties of hypothetical MOFs, diffusion and adsorption processes in MOFs, are reviewed. DFT calculations have been applied in the MOF area to study chemical stability; mechanical, photophysical, optical, and magnetic properties; photoluminescence; porosity; and semiconductor or metallic character. The prediction of MOF analogs with open-metal sites, studies of chemical bonding and the prediction of energies by quantum mechanics allows reducing experimental efforts in the creation of MOF/polymer membranes, adsorbents for CO2 uptake, separation of C2H2/CH4, C2H2/CO2, and inert gases, radionuclides sequestration, and water adsorption, as well as other promising advances. For the MOF-derived carbons, a lack of profound DFT investigations is currently observed, being mainly restricted to the electrocatalysis area (nitrogen reduction reaction, oxygen evolution reaction, and hydrogen evolution reaction), resulting applications in batteries and other storage devices, CO2 sequestration, and absorbance of organic substances.