Metal–organic frameworks (MOFs) have received a lot of attention because of their diverse structures, tunable properties and multiple applications such as gas storage, catalysis and magnetism. Recently, there has been a rapidly growing interest in developing MOF-based materials for electrochemical energy storage. MOFs have proved to be particularly suitable for electrochemical applications because of their tunable chemical composition that can be designed at the molecular level and their highly porous framework in which fast mass transportation of the related species is favorable. In this review, the recent progress in fabricating MOFs and MOF-derived nanostructures for electrochemical applications is presented. The review starts with an introduction of the principles and strategies for designing targeted MOFs followed by a discussion of some novel MOF-derived structures and their potential applications in electrochemical energy storage and conversion. Finally, major challenges in electrochemical energy storage are highlighted and prospective solutions from current progress in MOF-based nanostructure research are given.

Metal–organic frameworks and their derived nanostructures for electrochemical energy storage and conversion

Core–shell structured ZIF-8@ZIF-67 crystals are well-designed and prepared through a seed-mediated growth method. After thermal treatment of ZIF-8@ZIF-67 crystals, we obtain selectively functionalized nanoporous hybrid carbon materials consisting of nitrogen-doped carbon (NC) as the cores and highly graphitic carbon (GC) as the shells. This is the first example of the integration of NC and GC in one particle at the nanometer level. Electrochemical data strongly demonstrate that this nanoporous hybrid carbon material integrates the advantageous properties of the individual NC and GC, exhibiting a distinguished specific capacitance (270 F·g–1) calculated from the galvanostatic charge–discharge curves at a current density of 2 A·g–1. Our study not only bridges diverse carbon-based materials with infinite metal–organic frameworks but also opens a new avenue for artificially designed nanoarchitectures with target functionalities.

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Thermal Conversion of Core–Shell Metal–Organic Frameworks: A New Method for Selectively Functionalized Nanoporous Hybrid Carbon

Efficient reversible oxygen electrodes for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are vitally important for various energy conversion devices, such as regenerative fuel cells and metal–air batteries. However, realization of such electrodes is impeded by insufficient activity and instability of electrocatalysts for both water splitting and oxygen reduction. We report highly active bifunctional electrocatalysts for oxygen electrodes comprising core–shell Co@Co3O4 nanoparticles embedded in CNT-grafted N-doped carbon-polyhedra obtained by the pyrolysis of cobalt metal–organic framework (ZIF-67) in a reductive H2 atmosphere and subsequent controlled oxidative calcination. The catalysts afford 0.85 V reversible overvoltage in 0.1 m KOH, surpassing Pt/C, IrO2, and RuO2 and thus ranking them among one of the best non-precious-metal electrocatalysts for reversible oxygen electrodes.

Co@Co3O4 Encapsulated in Carbon Nanotube-Grafted Nitrogen-Doped Carbon Polyhedra as an Advanced Bifunctional Oxygen Electrode.

The emergence of metal-organic frameworks (MOFs) as a new class of crystalline porous materials is attracting considerable attention in many fields such as catalysis, energy storage and conversion, sensors, and environmental remediation due to their controllable composition, structure and pore size. MOFs are versatile precursors for the preparation of various forms of nanomaterials as well as new multifunctional nanocomposites/hybrids, which exhibit superior functional properties compared to the individual components assembling the composites. This review provides an overview of recent developments achieved in the fabrication of porous MOF-derived nanostructures including carbons, metal oxides, metal chalcogenides (metal sulfides and selenides), metal carbides, metal phosphides and their composites. Finally, the challenges and future trends and prospects associated with the development of MOF-derived nanomaterials are also examined.

Nanoarchitectured Design of Porous Materials and Nanocomposites from Metal-Organic Frameworks.

Nanoporous carbons possessing high surface area and narrow pore size distribution are among the most important classes of porous materials that are practically utilized in industries. Recently, several metal-organic frameworks (MOFs) or porous coordination polymers (PCPs) have been demonstrated as promising precursors to create functional nanoporous carbons. In this highlight article, we briefly review the recent progress in preparation of these novel MOF-derived nanoporous carbons. Some promising applications in energy and environment-related areas and future outlook are also discussed.

Yelin Kim

Papers

Porous carbon materials with a controllable surface area synthesized from metal-organic frameworks.

Hierarchical Porous Carbon Materials Prepared by Direct Carbonization of Metal–Organic Frameworks as an Electrode Material for Supercapacitors