A UiO type MOF with Lewis basic bipyridyl sites was synthesized and structurally characterized. After being activated by Soxhlet-extraction, this MOF exhibits high storage capacities for H 2 , CH 4 and CO 2 , and shows unusual stepwise adsorption for liquid CO 2 and solvents, indicating a sequential filling mechanism on different adsorption sites.Developing an effective system for carbon dioxide capture from anthropogenic emissions and finding appropriate mediums for energy gas (i.e., H 2 and CH 4 ) storage have been long term challenges, and will be increasingly urgent in future. 1 Physical sorption using solid state absorbents provides efficient alternatives owing to fast kinetics and high energy efficiency. 2 Indeed, some pilot plants for carbon dioxide capture and methane storage using solid state absorbents have been realized by some research groups. 3 Established as a new class of crystalline porous materials, metal-organic frameworks (MOFs) provide ideal platforms for such applications due to their intriguing structures, high surface area and tuneable functional pore environments. 4 In order to achieve high gas storage capacities or high selectivity, extensive efforts have been devoted to increase the affinity of frameworks with gas molecules, such as generating open metal sites 5 or tuning pore environments by immobilizing functional groups on the pore surface. 6 Immobilizing functional groups appears to be a promising strategy to tune the adsorption properties, especially for enhancing CO 2 binding strength by incorporating Lewis basic sites. However, the conventional strategy of anchoring the functional groups has some drawbacks. Along with the modification of the pore environments, the space occupation or blockage of functional groups always decreases the pore volume as well as specific surface areas significantly, which contrariwise lower the gas uptake capacities. 7 In this respect, the N-heterocyclic ligands are more attractive due to their benefits of constructing isomorphic MOFs and incorporating functional Lewis basic sites into the pore surface without declining their original pore spaces. 8 The UiO types of MOFs are an emerging class of MOFs that attract broad interest. 9 The highly porous structures and excellent stability of these types of MOFs allow them to be promising materials for the targets of CO 2 capture and energy gas storage. Up to now, extensive studies have been conducted based on UiO MOFs and their derivatives synthesized by functionalization/ modification on organic linkers. 10 Nevertheless, the gas sorption studies on UiO type MOFs incorporating Lewis basic pyridyl sites have never been investigated so far. The outstanding structural characteristics and excellent stability of UiO type MOFs motivate us to incorporate the pyridyl moieties into the frameworks, with the anticipation that it would further enhance the gas uptake capacities by anchoring the Lewis basic sites onto the pore surface but without sacrificing its original high porosity and exceptional robustness. He...
A novel nanoporous metal−organic framework NPC-4 with excellent thermal stability was assembled from 2,3,5,6-tetramethylbenzene-1,4-diisophthalate (TMBDI) and the paddle-wheel secondary building unit (Cu 2 (COO) 4 ). The porous structure comprises a single type of nanoscale cage (16 Å diameter) interconnected by windows (5.2 × 6.3 Å), which give a high pore volume. CH 4 (195−290 K), CO 2 (198−303 K), N 2 (77 K), and H 2 (77 K) adsorption isotherms were studied for pressures up to 20 bar. NPC-4 exhibits excellent methane and carbon dioxide storage capacities on a volume basis with very high adsorbate densities, under ambient conditions. Isobars were investigated to establish the relationship for adsorption capacities over a range of storage temperatures. The isosteric enthalpies of adsorption for both CH 4 and CO 2 adsorption did not vary significantly with amount adsorbed and were ∼15 and ∼25 kJ mol −1 , respectively. The adsorption/desorption kinetics for CH 4 and CO 2 were investigated and activation energies, enthalpies of activation, and diffusion parameters determined using various kinetic models. The activation energies for adsorption obtained over a range of uptakes from the stretched exponential kinetic model were 5.1− 6.3 kJ mol −1 (2−13.5 mmol g −1 ) for CO 2 and 2.7−5.6 kJ mol −1 (2−9 mmol g −1 ) for CH 4 . The activation energies for surface barriers and diffusion along pores for both CH 4 and CO 2 adsorption obtained from a combined barrier resistance diffusion model did not vary markedly with amount adsorbed and were <9 kJ mol −1 . Comparison of kinetic and thermodynamic parameters for CH 4 and CO 2 indicates that a surface barrier is rate determining at high uptakes, while intraparticle diffusion involving diffusion through pores, consisting of narrow windows interconnecting with nanocages, being rate determining at very low uptakes. The faster CH 4 intraparticle adsorption kinetics compared with CO 2 for NPC-4 was attributed to faster surface diffusion due to the lower isosteric enthalpy of adsorption for CH 4 .
Silver nanoclusters (AgNCs) were first coated with bovine serum albumin (BSA) and then encapsulated into porous metal-organic frameworks of ZIF-8 by the protein-mediated biomineralization process. Unexpectedly, the fluorescence intensities of the yielded AgNCs-BSA@ZIF-8 nanocomposites were discovered to be continuously enhanced during each of the BSA coating and ZIF-8 encapsulation steps. Compared to common AgNCs, greatly improved photostability and storage stability of AgNCs could also be expected. More importantly, having benefited from the ZIF-8 shells, the prepared nanocomposites could possess the specific accumulation and sensitive response to Cu ions, resulting in the rational quenching of their fluorescence intensities. Moreover, AgNCs-BSA@ZIF-8 nanocomposites were coated onto the hydrophobic arraying slides toward a microdots array-based fluorimetric method for the fast and sensitive evaluation of Cu ions. It was discovered that the developed fluorimetric strategy could ensure the high-throughput analysis of Cu ions in wide pH range, and especially some harsh and high-salt media. It can allow for the detection of Cu ions in blood with the concentrations ranging from 4.0 × 10 to 160 μM, thus serving as a new copper detection candidate to be widely applied in clinical test, food safety, and environmental monitoring fields.
Benefitting from large space and semiconductor properties of PTCDI, a PTCDI electrode was constructed for PIBs. The electrode displays an excellent performance in optimized electrolytes which can be attributed to fast electron and ion transport kinetics.
ABSTRACT:We report the preparation of ordered porous carbons for the first time via nanocasting zeolite 10X with an aim to evaluate their potential application for hydrogen storage. The synthesized carbons exhibit large Brunauer-Emmett-Teller surface areas in the 1300−3331 m 2 /g range and pore volumes up to 1.94 cm 3 /g with a pore size centered at 1.2 nm. The effects of different synthesis processes with pyrolysis temperature varied in the 600−800°C range on the surface areas, and pore structures of carbons were explored. During the carbonization process, carbons derived from the liquid−gas two-step routes at around 700°C are nongraphitic and retain the particle morphology of 10X zeolite, whereas the higher pyrolysis temperature results in some graphitic domains and hollow-shell morphologies. In contrast, carbons derived from the direct acetylene infiltration process have some incident nanoribbon or nanofiber morphologies. A considerable hydrogen storage capacity of 6.1 wt % at 77 K and 20 bar was attained for the carbon with the surface area up to 3331 m 2 /g, one of the top-ranked capacities ever observed for large surface area adsorbents, demonstrating their potential uses for compacting gaseous fuels of hydrogen. The hydrogen capacity is comparable to those of previously reported values on other kinds of carbon-based materials and highly dependent on the surface area and micropore volume of carbons related to the optimum pore size, therefore providing guidance for the further search of nanoporous materials for hydrogen storage. KEYWORDS: porous carbons, adsorption, nanocasting, zeolite template, hydrogen storage
■ INTRODUCTIONRecently, hydrogen as an alternative to fossil fuel has been recognized as an attractive energy carrier and fuel in the near future because it has high energy densities and creates neither air pollution nor greenhouse gas emissions.1−3 The main drawback for hydrogen as a transportation fuel is the lack of an effective storage method, which is yet to reach the criterions set by the DOE (Department of Energy, USA) for on-board application. Hence the development of cost-effective and feasible materials to satisfy on-board application claim for hydrogen storage is a great challenge. 4−7 Up to now, large numbers of adsorbents have been under intensive studies for hydrogen storage, and porous carbons with high surface areas and large pore volumes are considered as promising candidates for application as the hydrogen storage media. 8−12 The wide pore size distributions (PSDs) of conventional activated carbons in both the micro-and mesopore ranges will greatly affect their storage performance.13 Therefore, it is not difficult to imagine that preparation of carbons with a narrow PSD is very important in determining their adsorption performance. The template carbonization route is a versatile and well fitted methodology for the preparation of porous materials especially for the carbon-based materials with a controlled architecture and relative narrow PSD. 11,14−16 The template method usually...
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