Due to their high pore volume and high porosity, Metal-Organic Frameworks (MOFs), containing one-, two-, and three-dimensional structures, have been developing at an accelerating rate, especially for the adsorption studies. Herein, the adsorption separation mechanisms are being investigated. An adsorption-based separation can be governed by the size exclusion, through the difference in affinity, and separation by the difference in the adsorption rate. As the high potential of MOFs in the field of separation is visible, one must gain an understanding of the underlying process, under which, the separation occurs. Moreover, recent advancements of MOFs’ chemistry were studied, in addition to the structural characteristics of MOFs. The synthesis technique is also an integral part of exploiting MOFs for separation purposes. Thus, a brief review of the novel approaches used for MOFs synthesis has been carried out. Since the aim of this review is divulging the adsorption-based separation, two of the most significant applications of MOFs namely carbon-dioxide capture and methane storage were explored.