# A Review of Lithium-Sulfur Batteries Based on Metal-Organic Frameworks: Progress and Prospects
### Metal-Organic Frameworks: Promising Materials for Lithium-Sulfur Batteries Applications
#### 1.2.2 Preparation of Metal-Organic Framework Materials  
In recent years, considerable efforts have been dedicated to improving the performance of metal-organic frameworks (MOFs) through their integration with diverse functional materials, including carbon polymers, enzymes, graphene, and metal nanoparticles (NPs). This integration has facilitated the development of composite materials that possess superior properties and exhibit broader application prospects. The resultant MOF composites not only exhibit enhanced intrinsic properties contributed by the individual components but also showcase novel physicochemical properties arising from synergistic effects. The integration of MOFs and functional materials is anticipated to pave the way for advanced energy technologies.  
The preparation principles of the aforementioned four metal-organic framework (MOF) composites will be concisely outlined, with Figure 3a-d providing schematic diagrams illustrating the structure of each composite.  
1. MOF composites with polymers: Polymers are characterized by their flexibility, strength, and processability, in contrast with the crystalline and rigid nature of MOFs. By combining them, their respective advantages can be preserved. Several methods can be employed to achieve MOF-polymer composites. One approach involves blending MOFs with polymers to create a hybrid matrix film. Another method consists of covalently attaching polymers to the surface of the MOFs [39].
2. MOF and enzyme composite: MOFs serve as carriers for enzyme immobilization, with incorporation methods broadly categorized into the co-precipitation embedding  
Figure 2: Advantages of MOF as a battery cathode material (reprinted/adapted with permission from [38]; copyright 2024, _Science_).  
method and the biomineralization encapsulation method. In the co-precipitation method, auxiliary stabilizers are utilized to maintain the enzyme's active form during the preparation process, ensuring encapsulation of the enzyme within the MOF structure. Alternatively, biomimetic mineralization, which does not require co-precipitants, involves directly mixing the enzyme with its corresponding MOF to form enzyme-MOF bio-complexes [40]. The key distinction lies in the location of the enzyme: in the former method, it is encapsulated inside the MOF, whereas in the latter, it is associated with the exterior of the MOF.
3. MOF and graphene composites: The preparation of graphene/MOF composites typically involves three methods: in situ growth, interfacial growth, and co-molding. In the in situ growth method, the graphene matrix serves as a template to induce the growth of MOFs on its surface and within its internal pores. Alternatively, the interfacial growth and co-molding methods are employed to form composites by uniformly dispersing MOFs in a graphene solution, either through physical mixing or chemical binding [41].
4. MOFs and metal nanoparticles (NPs): MOFs materials are used as the main materials, and the precursors of metal NPs are confined in the limited space of MOFs materials by the one-pot method, solution impregnation, vapor-phase deposition and solid-state milling, and then the size and morphology of the metal NPs are achieved by adding reductants or energizing the reducing gases, etc. These materials not only inherited the porous nature of MOFs but also combined with the high catalytic activity of metal nanoparticles, which makes the composites exhibit higher efficiency and selectivity in catalytic reactions [42].