Metal-organic frameworks (MOFs) are a form of porous and crystalline material created by combining metal ions and organic linkers and received greater attention because of their distinctive structure and widespread uses in a variety of applications such as gas storage and separation, catalysis, enzyme immobilization, drug delivery, water capture, and sensing. Various well-designed MOF-based composites that combine MOFs with other feature materials such as nanoparticles, quantum dots, natural enzymes, or polymers with notably improved or unique capabilities have recently been described compared with single components. MOFs have been used as provision substrates for nanomaterials and sacrificial templates/precursors in the preparation of various functional nanostructures. The structural-functional relations and role of MOFs are crucial for understanding to synthesize high-performance MOF-based composites effectively and directionally for specific applications. The porosity of MOFs is regarded as one of their most promising properties, as it allows for space on the micro- and meso-scales, thus constraining and exposing their functionalities. MOF research has focused on designing MOFs with high porosity and increasing effective activation methods for conserving and gaining access to their pore space. The most recent advancement of MOFs as precursors for the synthesis of various nanostructures and their possible applications are investigated in this paper. The practical activities of MOFs are categorized and explored through several instances, which can help chemical users comprehend the structural/functional link in MOF-based composites from a new perception. Finally, a perspective on future problems and possible opportunities for high porosity MOFs in various applications is discussed.