Unlike an intercalation cathode, which has an intrinsic host structure made of redox metal sites allowing the transport of Li⁺/e⁻, sulfur as a conversion cathode requires an additional host to store and immobilize the mobile redox centers, polysulfides. Metal–organic frameworks (MOFs) as a class of highly porous and well-defined crystalline materials are a promising platform to search for an effective host through rational design. With the appropriate selection of an electrolyte and a cutoff voltage range, sulfur stored in an appropriate MOF host can take advantage of both intercalation (fast and stable) and conversion (high energy density) cathodes. Herein, we describe a fast cathode with long cycle life based on sulfur and ZIF-8 nanocrystals. With 30 wt% sulfur loading in the electrode, it achieves remarkable discharge capacities of 1055 mA h g⁻¹ (based on sulfur) at 0.1 C and 710 mA h g⁻¹ at 1 C. The decay over 300 cycles at 0.5 C is 0.08% per cycle, prominent in long-cycle Li–S batteries. By comparing with another three distinct MOFs, MIL-53 (Al), NH₂-MIL-53 (Al) and HKUST-1, as well as two sets of ZIF-8 with particle sizes in the micrometer range, it reveals that (i) the small particle size of the MOF host is appreciable to achieve a high capacity and (ii) small apertures, associated with functionalities in the open framework that have affinity with the polysulfide anions, can help achieve a stable cycling. We believe that the findings are general and applicable for the rational design of new hosts for sulfur in other porous material families to produce more effective and stable Li–S batteries.

Developing noble metal free catalysts for the oxygen reduction reaction (ORR) is of critical importance for the production of low cost polymer electrolyte membrane fuel cells. In this paper, metal organic frameworks (MOFs) are used as precursors to synthesize ORR catalysts via pyrolysis in an inert atmosphere. The ORR performance is found to be closely associated with the metal/ligand combination in MOFs. The Co-imidazole based MOF (ZIF-67) derived catalyst exhibits the best ORR activity in both alkaline and acidic electrolytes. The Co cations coordinated by the aromatic nitrogen ligands in ZIF-67 may assist the formation of ORR active sites in the derived catalyst. The best ORR performance is obtained when the porosity of the derived catalyst is maximized, by optimizing the pyrolysis temperature and the acid leaching process. The performance of the best MOF derived catalyst is comparable to that of Pt/C in both alkaline and acidic electrolytes.

Graphene oxide (GO) sheets were introduced to stabilize the melted polyethylene glycol (PEG) during the solid–liquid phase change process, which can be used as a smart heat storage system. The structural properties and phase change behaviors of the PEG–GO composites were comprehensively investigated as a function of the PEG content by means of various characterization techniques. The highest stabilized PEG content is 90 wt% in the composites, resulting in a heat storage capacity of 156.9 J g⁻¹, 93.9% of the phase change enthalpy of pure PEG. Notably, GO has much stronger impact on lowering of the phase change temperature of PEG compared with some other porous carbon materials (activated carbon and ordered mesoporous carbon) due to the unique thin layer structure of GO. Because of the high heat storage capacity and the moderate phase change temperature, the PEG–GO composite is a promising heat energy storage candidate at mild temperature.