The high porosity of metal-organic frameworks (MOFs) has been used to achieve exceptional gas adsorptive properties but as yet remains largely unexplored for electrochemical energy storage devices. This study shows that MOFs made as nanocrystals (nMOFs) can be doped with graphene and successfully incorporated into devices to function as supercapacitors. A series of 23 different nMOFs with multiple organic functionalities and metal ions, differing pore sizes and shapes, discrete and infinite metal oxide backbones, large and small nanocrystals, and a variety of structure types have been prepared and examined. Several members of this series give high capacitance; in particular, a zirconium MOF exhibits exceptionally high capacitance. It has the stack and areal capacitance of 0.64 and 5.09 mF cm(-2), about 6 times that of the supercapacitors made from the benchmark commercial activated carbon materials and a performance that is preserved over at least 10000 charge/discharge cycles.

Lithium polysulphides generated during discharge in the cathode of a lithium-sulphur redox cell are important, but their dissolution into the electrolyte from the cathode during each redox cycle leads to a shortened cycle life. Herein, we use in situ spectroelectrochemical measurements to demonstrate that sp2 nitrogen atoms in the organic linkers of nanocrystalline metal-organic framework-867 (nMOF-867) are able to encapsulate lithium polysulphides inside the microcages of nMOF-867, thus helping to prevent their dissolution into the electrolyte during discharge/charge cycles. This encapsulation mechanism of lithiated/delithiated polysulphides was further confirmed by observations of shifted FTIR spectra for the C = N and C-N bonds, the XPS spectra for the Li-N bonds from nMOF-867, and a visualization method, demonstrating that nMOF-867 prevents lithium polysulphides from being dissolved in the electrolyte. Indeed, a cathode fabricated using nMOF-867 exhibited excellent capacity retention over a long cycle life of 500 discharge/charge cycles, with a capacity loss of approximately 0.027% per cycle from a discharge capacity of 788 mAh/g at a high current rate of 835 mA/g.

A metal−organic framework (MOF) with a specific construction and pores was demonstrated to have many advanced properties, but still limited to having unique aspects arising from the combination of different MOFs in a single body. Here, we report a facile method to produce MOF-5 crystals with nanocrystalline HKUST-1 (nHKUST-1) embedded into them in what is termed the "nHKUST-1⊂MOF-5" structure. The results show that the nHKUST-1⊂MOF-5 structure is capable of molecular encapsulation by trapping dye molecules in nHKUST-1 particles and embedding them in MOF-5 crystals. Moreover, the gravimetric uptake capacity of nHKUST-1⊂MOF-5 for methane (CH 4 ) was found to be enhanced as compared to that of MOF-5 or nHKUST-1 alone such that the nHKUST-1⊂MOF-5 structure exhibits a volumetric capacity of 250% for fuel storage deliverable by the CNG tank at room temperature and 80 bar. Furthermore, it showed robust capacity retention for reversible CH 4 uptake cycles at room temperature.

We report that ammonia borane with a high uptake capacity for hydrogen can be encapsulated in a metal-organic framework (MOF) via capillary action, where the MOF functions as a chemical guide to control the hydrogen desorption pathways of ammonia borane by releasing only pure hydrogen, lowering its hydrogen desorption temperature, and suppressing its volumetric expansion during hydrogen desorption.