Metal-organic frameworks (MOFs) have recently emerged as a type of uniformly and periodically atom-distributed precursor and efficient self-sacrificial template to fabricate hierarchical porous-carbon-related nanostructured functional materials. For the first time, a Cu-based MOF, i.e., Cu-NPMOF is used, whose linkers contain nitrogen and phosphorus heteroatoms, as a single precursor and template to prepare novel Cu3 P nanoparticles (NPs) coated by a N,P-codoped carbon shell that is extended to a hierarchical porous carbon matrix with identical uniform N and P doping (termed Cu3 P@NPPC) as an electrocatalyst. Cu3 P@NPPC demonstrates outstanding activity for both the hydrogen evolution and oxygen reduction reaction, representing the first example of a Cu3 P-based bifunctional catalyst for energy-conversion reactions. The high performances are ascribed to the high specific surface area, the synergistic effects of the Cu3 P NPs with intrinsic activity, the protection of the carbon shell, and the hierarchical porous carbon matrix doped by multiheteroatoms. This strategy of using a diverse MOF as a structural and compositional material to create a new multifunctional composite/hybrid may expand the opportunities to explore highly efficient and robust non-noble-metal catalysts for energy-conversion reactions.

MOF-Derived Bifunctional Cu3 P Nanoparticles Coated by a N,P-Codoped Carbon Shell for Hydrogen Evolution and Oxygen Reduction.

Sodium-ion batteries (SIBs) are considered to be a low-cost complement or competitor to Li-ion batteries for large-scale electric energy storage applications; however, their development has been less successful due to the lack of suitable host materials to enable reversible Na+ insertion reactions. Prussian blue analogs (PBAs) appear to be attractive candidates for SIB cathodes because of their open channel structure, compositional and electrochemical tunability. In this paper, the authors present a comprehensive review on the recent advances in the development of PBA frameworks as SIB cathodes with particular attention to the structure-performance correlation of the PBA materials, and discuss the possible strategies to address the problems present in the SIB applications of PBAs. Also, the development of the PBA frameworks for the insertion cathodes of other monovalent and multivalent ions is briefly introduced, with the aim of providing a new insight into the design and development of new host materials for the next-generation advanced batteries.

Prussian Blue Cathode Materials for Sodium-Ion Batteries and Other Ion Batteries

Advanced Carbon-Based Anodes for Potassium-Ion Batteries

Metal organic framework (MOF)-derived nanoporous carbons (NPCs) have been proposed as promising electrode materials for energy storage and conversion devices. However, MOF-derived NPCs typically suffer from poor electrical conductivity due to the lack of connectivity between these particles and a micropore-dominated storage mechanism, which hinder mass and electron transfer, thereby leading to poor electrochemical performance. In recent years, one-dimensional (1D) MOF-derived carbon nanostructures obtained using an electrospinning method have emerged as promising materials for both electrochemical energy storage (EES) and energy conversion applications. In this mini review, the recent progress in the development of MOF-derived 1D porous or hollow carbon nanofibers using the electrospinning method and their application in energy storage (e.g., supercapacitors and rechargeable batteries) and conversion devices (e.g., fuel cells) is presented. The synthetic method, formation mechanism and the structure–activity relationship of such porous or hollow carbon nanofibers are also discussed in detail. Finally, future perspectives on the development of electrospun MOF-derived carbon nanomaterials for energy storage and conversion applications are provided. This review will provide some guidance for future derivations of 1D hollow carbon nanomaterials from MOFs using electrospinning technology.

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Metal–organic framework-derived one-dimensional porous or hollow carbon-based nanofibers for energy storage and conversion

Hollow materials derived from metal-organic frameworks (MOFs), by virtue of their controllable configuration, composition, porosity, and specific surface area, have shown fascinating physicochemical properties and widespread applications, especially in electrochemical energy storage and conversion. Here, the recent advances in the controllable synthesis are discussed, mainly focusing on the conversion mechanisms from MOFs to hollow-structured materials. The synthetic strategies of MOF-derived hollow-structured materials are broadly sorted into two categories: the controllable synthesis of hollow MOFs and subsequent pyrolysis into functional materials, and the controllable conversion of solid MOFs with predesigned composition and morphology into hollow structures. Based on the formation processes of hollow MOFs and the conversion processes of solid MOFs, the synthetic strategies are further conceptually grouped into six categories: template-mediated assembly, stepped dissolution-regrowth, selective chemical etching, interfacial ion exchange, heterogeneous contraction, and self-catalytic pyrolysis. By analyzing and discussing 14 types of reaction processes in detail, a systematic mechanism of conversion from MOFs to hollow-structured materials is exhibited. Afterward, the applications of these hollow structures as electrode materials for lithium-ion batteries, hybrid supercapacitors, and electrocatalysis are presented. Finally, an outlook on the emergent challenges and future developments in terms of their controllable fabrications and electrochemical applications is further discussed.

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Hollow Functional Materials Derived from Metal-Organic Frameworks: Synthetic Strategies, Conversion Mechanisms, and Electrochemical Applications.

Three-dimensional (3D) networks of graphitic carbon are promising materials for energy storage and conversion devices because of their high electrical conductivity, which is promoted by the good interconnection between the carbon particles. However, it is still difficult to directly synthesize such carbon networks. Herein, we report the novel synthesis of 3D graphitic carbon networks through the pyrolysis of nanosized ZIF-67 crystals. Interestingly, the unusual effect of downsizing the ZIF-67 crystals and the incorporation of catalytic Co nanoparticles was the spontaneous formation of graphitic networks. The obtained graphitic carbon networks show excellent electrochemical performance for the insertion and extraction of potassium ions.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/anie.201701252

Spontaneous Weaving of Graphitic Carbon Networks Synthesized by Pyrolysis of ZIF-67 Crystals.

Few-layer graphitic shell networks show great promise in energy storage applications such as electrochemical accommodation of alkaline ions. However, the networking and graphitization processes remain a challenge because of the complicated procedures and high temperature used for fabrication. In this work, we report a simple synthetic method by employing low-temperature solid-state pyrolysis of ZIF-67 crystals to weave graphitic shells consisting of 3–10 layers into capsules. Owing to their unique structure, the few-layer graphitic shell networks show excellent electrochemical performance for fast sodium ion storage.

Yinxiang Chen

Papers

Spontaneous Weaving of Graphitic Carbon Networks Synthesized by Pyrolysis of ZIF-67 Crystals.

Few-layer graphitic shells networked by low temperature pyrolysis of zeolitic imidazolate frameworks