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.

The combustion of hydrocarbon fuels to satisfy the current energy requirements increases the emission of gases that contribute to global-warming [1] and thus to climate change, such as carbon dioxide (CO 2 ). Porous structures including COFs (covalent organic frameworks), [2] PIMs (polymers of intrinsic microporosities), [3] HCPs (hyper-cross-linked polymers), [4] CMPs (conjugated microporous polymers), [1c,5] and CTFs (covalent triazine-based frameworks) [6] have been considered to be very successful in capturing CO 2 with high capacities. Meanwhile, there is still the great challenge of realizing highly selective CO 2 -capturing materials for practical use in ambient conditions, which could allow many practical applications and help to significantly slow the greenhouse effect.Herein, we report new highly selective CO 2 -capturing polymeric organic networks (PONs) synthesized using (methanetetrayltetra-4,1-phenylene)tetrakisboronic acid and three kinds of halogen-substituted struts that include heterocyclic groups. The structures and morphology of the networks are studied by solid-state NMR, Fourier-transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM). PON-1 has only phenyl group, while PON-2 and -3 contain pyridyl and thiophenyl groups, respectively. While all the PONs have moderate surface areas, they are very attractive for use in capturing a large amount of CO 2 under ambient conditions. Moreover, it was found that PONs offer high selective adsorption for CO 2 over CH 4 and H 2 under ambient conditions.(Methanetetrayltetra-4,1-phenylene)tetrakisboronic acid [8] has been used as a tetrahedral building unit to assemble into highly porous three-dimensional network structures. It also has the potential to react with various dihalogenated struts, and there are many useful coupling reactions between boronic acids and halogen atoms on diverse aromatic and heterocyclic compounds. [7] For the efficient synthesis of porous structures, we selected representative conditions of the coupling reaction using (methanetetrayltetra-4,1-phenylene)tetrakisboronic acid and 1,4-dibromobenzene to give a tetrahedral structure (Supporting Information, Table S1). The reactions were carried out at 90 °C in the presence of water for 5 days to give sufficient reaction times. Except under conditions using toluene and 1,2-dimethoxyethane (DME), we found that insoluble polymers were produced. Next, the polymers recovered after filtration were washed with CH 2 Cl 2 , HCl solution, MeOH, and acetone and dried for 3 days at 150 °C in a vacuum. Despite the excess washing, some polymer networks exhibited yields in excess of 100%. This observation implies that the condensation rate is lower than expected, thus some reactants remain and contribute to the sample mass. [5e,5f ] The Brunauer-Emmett-Teller (BET) method was used to determine the surface areas using desorption branches over 0.05-0.25 P P 0 −1 of Ar isotherm at 87 K. [2d] The reaction without water was found not to res...

A hierarchical Si hydrogel architecture with conductive polyaniline channels on sulfonated-graphene gives high capacity, in addition to excellent capacity retention and robust cycle life.

A multi metal (M: Fe, Co, and Ni)-doped rectangular ZnO nanocrystal (r-ZnO:M) was synthesised using nanocrystalline metal-organic framework-5 (n-MOF-5). After calcination in air, M-inserted n-MOF-5 led to r-ZnO:M of the wurtzite crystal structure with a small amount (<1%) of spinel ZnM2O4 phase. The inserted metal atoms of r-ZnO:M, replacing the Zn atoms of the wurtzite ZnO structure, were well-dispersed throughout the nanocrystal. Density functional theory calculations not only confirm the structural stability of wurtzite r-ZnO:M and negligible contribution of spinel ZnM2O4 but also elucidate the experimentally observed increase of visible light absorbance and appearance of ferromagnetism upon metal atom doping.

CH NH PbI is one of the promising light sensitizers for perovskite photovoltaic cells, but a thick layer is required to enhance light absorption in the long-wavelength regime ranging from PbI absorption edge (500 nm) to its optical band-gap edge (780 nm) in visible light. Meanwhile, the thick perovskite layer suppresses visible-light absorption in the short wavelengths below 500 nm and charge extraction capability of electron-hole pairs produced upon light absorption. Herein, we find that a new light scattering layer with the mixed cavities of sizes in 100 and 200 nm between transparent fluorine-doped tin oxide and mesoporous titanium dioxide electron transport layer enables full absorption of short-wavelength photons (λ < 500 nm) to the perovskite along with enhanced absorption of long-wavelength photons (500 nm < λ < 780 nm). Moreover, the light-driven electric field is proven to allow efficient charge extraction upon light absorption, thereby leading to the increased photocurrent density as well as the fill factor prompted by the slow recombination rate. Additionally, the photocurrent density of the cell with a light scattering layer of mixed cavities is stabilized due to suppressed charge accumulation. Consequently, this work provides a new route to realize broadband light harvesting of visible light for high-performance perovskite photovoltaic cells.