A review on the field patents and recent developments over the application of metal organic frameworks (MOFs) in supercapacitors

Global energy demand and the seriousness in sustainable energy obligations along with a large amount of CO2 emission and rapid depletion of fossil fuels have diligently persuaded the researchers to promote eco-benign energy storage systems with high performance. High energy and power density, long cycling life, ultra-flexibility, environment friendly, light-weight with challenges of the benefits of industrial applications, safety, and reliability are currently considered in inventing efficient energy storage systems. Therefore, promoting and employing effective technologies to storing energy has widely become a development trend. Achieving that object is paved by developing batteries and supercapacitors (SCs) which are remarkably attracted enormous research interest and scientific reports. Supercapacitors are on a rapid and significant development path, with possessing desirable electrochemical benefits, including high power density, long cycle-life, rapid charge–discharge rate, and absolutely demanded commercial features. To understand the real performance of investigated supercapacitors, we considered the electrochemical output of applied SC systems. Actually, various types of electrode materials, electrolytes, have been significantly used to improve the electrochemical features in terms of specific capacitance, energy density, power density, and cycle life. Here, we focused on reviewing filed patents on application of MOFs in SCs and the recent improvements in employed components consisting of electrode and electrolyte in supercapacitive behavior. From the technical results, ZIF-series, UiO-66/67, MIL-based, MOF-74, MOF-5, Ni3(HITP)2, Cu3(HITP)2 are widely used in MOF-based SCs. Patents are costly to register and they are also extremely reliable documents that are remarkably reliable in comparison to articles. Because patents are seriously challenged scientifically and legally, they contain critical information that inventors must disclose in full detail. Compared to articles, patents are a truly reliable reference for all researchers, especially youthful researchers, start-ups, and technology developers, due to their complete disclosure, reproducibility and 100% reliability. While innovation is a key component in both papers and patents, patents certainly contain an Inventive Step (IS), which is the main criterion that distinguishes these two references. Furthermore, mixed-metal MOF and compositing materials such as PANI (conductive polymers), graphene, CNTs, and nanomaterials or using as precursor material, provide higher surface area, simultaneous EDLC and pseudocapacitance effect which is desirable for electrochemical devices. Among considered files, only 135 patents were closely related to this subject showing its stepping-stone age. In addition, the aqueous electrolyte such as KOH and H2SO4 are well-demanded to ease charge transfer in SCs. The statistical analysis showed that China is leading developer towards developing MOF-based SCs; while, the USA and South Korea are two next following countries. China seems to have a very large market share for this type of SC. The USA, EU, and South Korea, despite their close economic share and market share, need to sacrifice more diligent efforts in competition with China. We believe that this review opens a new prospective of MOF-based SCs for future electrochemical considering to provide higher performed devices.