# A Review of Lithium-Sulfur Batteries Based on Metal-Organic Frameworks: Progress and Prospects
## 2 Metal-Organic Frameworks for Cathode Applications in Lithium-Sulfur Batteries
### Metal-Organic Framework Composites
#### 2.2.4 Derivatives of Metal-Organic Frameworks  
The utilization of MOF-derived composite materials in LSBs represents an emerging and dynamic research area. These materials can undergo transformations into nanostructured composites comprising porous carbon and metal/metal compounds via methodologies encompassing carbonization, pyrolytic acid treatment, and osmotic dehydration [61; 62]. These MOF derivatives maintain their porous structure, exhibiting superior electrical conductivity and a wealth of polar or catalytic sites [63], which can substantially decrease  
Figure 8: (**a**) Illustration for the preparation processes of 3 CPC@S composites. (**b**) Initial discharge/charging curves of 3 CPC@S, PANI@S, and NC@S cathodes at 0.1 C (reprinted/adapted with permission from [59]; copyright 2023, _Colloids and Surfaces A: Physicochemical and Engineering Aspects_). (**c**) Schematic of the fabrication of ZIF-67 and ZIF-67@PANI (reprinted/adapted with permission from [60]; copyright 2021, _Journal of Alloys and Compounds_). electrochemical polarization and enhance the redox kinetics in LSBs [64]. [PERSON] et al. [65] designed a bi-directional catalyst based on In-MOF by adjusting the phases of MOF derivatives at different carbonation temperatures, as shown in Figure 9a. As a result, In\({}_{2}\)O\({}_{3}\)@C obtained at 400 \({}^{\circ}\)C promotes the conversion of S\({}_{8}\) to soluble long-chain Li\({}_{2}\)S\({}_{n}\) (\(4\leq n\leq 8\)), while In@C obtained at 1000 \({}^{\circ}\)C shows excellent catalytic performance in promoting the conversion of Li\({}_{2}\)S\({}_{4}\) to Li\({}_{2}\)S and the dissolution of Li\({}_{2}\)S. In-In\({}_{2}\)O\({}_{3}\)@C prepared at 800 \({}^{\circ}\)C combines the advantages of the above two derivatives and can catalyze the conversion of lithium-ion batteries in both directions. In Figure 9b, it can be clearly observed that the exchange current density (I0) of In-In\({}_{2}\)O\({}_{3}\)@C is much higher than that of In@C and In\({}_{2}\)O\({}_{3}\)@C during the conversion of LiPSs, which suggests that In-In\({}_{2}\)O\({}_{3}\)@C is more conducive to accelerating the kinetics of the redox reaction of LiPSs. The carbonization of bimetallic MOFs can lead to the formation of bimetallic nanoparticles, offering unique advantages that are unattainable with monometallic materials; Meanwhile, carbonization of nanofibers can result in the formation of unique, self-standing carbon nanofiber structures [66]. [PERSON] et al. [67] innovatively synthesized a composite material comprising nitrogen-doped carbon nanofibers loaded with MOF-derived NiCo bimetallic nanoparticles, designated as NiCo-PCNF [68; 69; 70]. This synthesis was achieved through a combination of advanced techniques: high-pressure electrospinning, in situ growth, and high-temperature pyrolysis, as illustrated in Figure 9c. The nickel-cobalt bimetallic nanoparticles derived from MOF can be clearly observed in Figure 9d, and the nickel-cobalt metal nanoparticles marked by red circles have a size of 20-40 nm attached to the surface and inner diameter of the carbon nanofibers. According to Figure 9e, the performance shows that the initial specific discharge capacity of the S/NiCo-PCNF cathode is 849.3 mAh g\({}^{-1}\), which is higher than the 836.9, 620.6, and 742.2 mAh g\({}^{-1}\) of S/Ni-PCNF, S/Co-PCNF, and S/PCNF. After 500 cycles, the Coulombic efficiency of the S/NiCo-PCNF cathode electrode reached 97.7%, with a decay rate of only 0.099% per cycle. This result further demonstrates the superior co-catalytic electrocatalytic ability of nickel-cobalt bimetallic nanoparticles in the overall sulfur reduction reaction (SRR), which effectively improves the kinetics of the redox reaction of LiPSs, utilizes the reactive species more fully, and exhibits excellent electrochemical cycling performance.