Despite the outstanding features of metal-organic frameworks (MOFs) such as high surface area, high porosity, abundance of metal nodes in the structure, and functionalized linkers, the potential use of metal centers in a variety of applications of these compounds is limited due to their binding to linkers or solvent molecules. Therefore, creating defects and forming defective MOFs with open metal centers are more suitable for a wide range of applications. Quasi-MOFs, as a new class of large-scale structural defective MOFs with high concentrations of unsaturated metal centers, have recently been considered due to ease of synthesis and enhanced efficiencies in major applications of MOFs in order to compensate for the disadvantages of MOFs. Herein, we provide an overview of the latest defect engineering in MOFs, and subsequently we present a comprehensive study of recent advances in various applications of Q-MOFs. This review is anticipated to provide great guidelines for various applications of quasi MOFs.