Metal-organic frameworks (MOFs), a new class of crystalline porous organic-inorganic hybrid materials, have recently attracted increasing interest in the field of energy storage and conversion. Herein, recent progress of MOFs and MOF composites for energy storage and conversion applications, including photochemical and electrochemical fuel production (hydrogen production and CO reduction), water oxidation, supercapacitors, and Li-based batteries (Li-ion, Li-S, and Li-O batteries), is summarized. Typical development strategies (e.g., incorporation of active components, design of smart morphologies, and judicious selection of organic linkers and metal nodes) of MOFs and MOF composites for particular energy storage and conversion applications are highlighted. A broad overview of recent progress is provided, which will hopefully promote the future development of MOFs and MOF composites for advanced energy storage and conversion applications.

Metal sites play an essential role in both electrocatalytic and photocatalytic energy conversion. The highly ordered arrangements of the organic linkers and metal nodes as well as the well-defined pore structures of metal-organic frameworks (MOFs) make them ideal substrates to support atomically dispersed metal sites (ADMSs) located in their metal nodes, linkers, and pores. Porous carbon materials doped with ADMSs can be derived from these ADMS-incorporating MOF precursors through controlled treatments. These ADMSs incorporated in pristine MOFs and MOF-derived carbon materials possess unique advantages over molecular or bulk metal-based catalysts and bridge the gap between homogeneous and heterogeneous catalysts for energy-conversion applications. This Review presents recent progress in the design and incorporation of ADMSs in MOFs and MOF-derived materials for energy-conversion applications.

Metal oxides and carbon-based materials are the most promising electrode materials for a wide range of low-cost and highly efficient energy storage and conversion devices. Creating unique nanostructures of metal oxides and carbon materials is imperative to the development of a new generation of electrodes with high energy and power density. Here we report our findings in the development of a novel graphene aerogel assisted method for preparation of metal oxide nanoparticles (NPs) derived from bulk MOFs (Co-based MOF, Co(mIM) (mIM = 2-methylimidazole). The presence of cobalt oxide (CoO) hollow NPs with a uniform size of 35 nm monodispersed in N-doped graphene aerogels (NG-A) was confirmed by microscopic analyses. The evolved structure (denoted as CoO/NG-A) served as a robust Pt-free electrocatalyst with excellent activity for the oxygen reduction reaction (ORR) in an alkaline electrolyte solution. In addition, when Co was removed, the resulting nitrogen-rich porous carbon-graphene composite electrode (denoted as C/NG-A) displayed exceptional capacitance and rate capability in a supercapacitor. Further, this method is readily applicable to creation of functional metal oxide hollow nanoparticles on the surface of other carbon materials such as graphene and carbon nanotubes, providing a good opportunity to tune their physical or chemical activities.

A multi-phase catalyst coating, composed of a thin-film PrBa 0.8 Ca 0.2 Co 2 O 5+d (PBCC) decorated with nanoparticles (NPs) of BaCoO 3Àx and PrCoO 3Àx , has dramatically enhanced the rate of oxygen reduction reaction. Oxygen molecules adsorb and dissociate rapidly on the NPs due to enriched surface oxygen vacancies, while the dissociated oxygen species transport quickly through the PBCC film into the cathode.

Yolk-shell nanostructures have received great attention for boosting the performance of lithium-ion batteries because of their obvious advantages in solving the problems associated with large volume change, low conductivity, and short diffusion path for Li ion transport. A universal strategy for making hollow transition metal oxide (TMO) nanoparticles (NPs) encapsulated into B, N co-doped graphitic nanotubes (TMO@BNG (TMO = CoO, Ni O , Mn O ) through combining pyrolysis with an oxidation method is reported herein. The as-made TMO@BNG exhibits the TMO-dependent lithium-ion storage ability, in which CoO@BNG nanotubes exhibit highest lithium-ion storage capacity of 1554 mA h g at the current density of 96 mA g , good rate ability (410 mA h g at 1.75 A g ), and high stability (almost 96% storage capacity retention after 480 cycles). The present work highlights the importance of introducing hollow TMO NPs with thin wall into BNG with large surface area for boosting LIBs in the terms of storage capacity, rate capability, and cycling stability.

Large carbon networks featuring hierarchical pores and atomically dispersed metal sites (ADMSs) are ideal materials for energy storage and conversion due to the spatially continuous conductive networks and highly active ADMSs. However, it is a challenge to synthesize such ADMS‐decorated carbon networks. Here, an innovative fusion‐foaming methodology is presented in which energetic metal–organic framework (EMOF) nanoparticles are puffed up to submillimeter‐scaled ADMS‐decorated carbon networks via a one‐step pyrolysis. Their extraordinary catalytic performance towards oxygen reduction reaction verifies the practicability of this synthetic approach. Moreover, this approach can be readily applicable to a wide range of unexplored EMOFs, expanding scopes for future materials design.

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We have successfully synthesized novel, nickel-based, pillared DABCO-MOFs (DMOFs) of similar topologies-[Ni(L)(DABCO) 0.5 ], where L is the functionalized BDC (1,4benzenedicarboxylic acid) linker and DABCO is 1,4-diazabicyclo[2.2.2]-octane. The stability of DMOF-ADC ([Ni(9,10-anthracenedicarboxylic acid)(DABCO) 0.5 ]) and DMOF-TM ([Ni(2,3,5,6tetramethyl-1,4-benzenedicarboxylic acid)(DABCO) 0.5 ]) in a humid environment was confirmed by surface area analysis on the water-exposed samples. When used as electrode materials, these DMOF capacitors exhibited excellent electrochemical performance. For example, a Ni-DMOF-ADC electrode showed specific capacitances of 552 and 438 F g-1 at current densities of 1 and 20 A g-1 , respectively, while maintaining outstanding cycling stability (capacitance retention of >98% after 16,000 cycles at current density of 10 A g-1) for MOF-derived materials based supercapacitors. The excellent electrochemical performance is attributed to the conversion of DMOFs to highly functionalized nickel hydroxide which inherited the high stability of DMOF-ADC and remained intact during charge-discharge process. Further, this work provides a general approach for the application of nickel-based pillared MOFs as relatively stable electrode in electrical energy storage.