Metal-organic frameworks (MOFs) were defined as secondary building units (SBUs) [metals] linked to organic (aromatic carboxylates are widely employed because they have rigid organic skeleton and strong coordination ability toward many metals). MOFs pay an important role in material science, because it has high surface areas, accessible permanent porosities, tunable structures, and high chemical and/or thermal stability. MOFs were synthesized by different methods such as solvothermal, hydrothermal, sonochemical & mechanical synthesis and microwave synthesis. MOFs have many applications in gas storage, separation, catalysis, sensors, and drug delivery. The main applications of MOFs rely upon the absorption and separation of gaseous molecules including CO2, N2, CH4, and H2; however, such an intriguing class of ultra porous materials is now holding promise for microelectronics, sensing, ion conductivity, optics, pollutant sequestration, drug delivery, contrast agents, micromotors, and bioreactors.