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1.
Postsynthetic modifications (PSMs) of metal–organic frameworks (MOFs) play a crucial role in enhancing material performance through open metal site (OMS) functionalization or ligand exchange. However, a significant challenge persists in preserving open metal sites during ligand exchange, as these sites are inherently bound by incoming ligands. In this study, for the first time, we introduced alkoxides by exchanging bridging chloride in Ni2Cl2BTDD (BTDD=bis (1H-1,2,3,–triazolo [4,5-b],–[4′,5′-i]) dibenzo[1,4]dioxin) through PSM. Rietveld refinement of synchrotron X-ray diffraction data indicated that the alkoxide oxygen atom bridges Ni(II) centers while the OMSs of the MOF are preserved. Due to the synergy of the existing OMS and introduced functional group, the alkoxide-exchanged MOFs showed CO2 uptakes superior to the pristine MOF. Remarkably, the tert-butoxide-substituted Ni_T exhibited a nearly threefold and twofold increase in CO2 uptake compared to Ni2Cl2BTDD at 0.15 and 1 bar, respectively, as well as high water stability relative to the other exchanged frameworks. Furthermore, the Grand Canonical Monte Carlo simulations for Ni_T suggested that CO2 interacts with the OMS and the surrounding methyl groups of tert-butoxide groups, which is responsible for the enhanced CO2 capacity. This work provides a facile and unique synthetic strategy for realizing a desirable OMS-incorporating MOF platform through bridging ligand exchange.  相似文献   

2.
Although numerous porous adsorbents have been investigated for NH3 capture applications, these materials often exhibit insufficient NH3 uptake, low NH3 affinity at the ppm level, and poor chemical stability against wet NH3 conditions. The NH3 capture properties of M2(dobpdc) complexes (M=Mg2+, Mn2+, Co2+, Ni2+, and Zn2+; dobpdc4−=4,4-dioxidobiphenyl-3,3-dicarboxylate) that contain open metal sites is presented. The NH3 uptake of Mg2(dobpdc) at 298 K was 23.9 mmol g−1 at 1 bar and 8.25 mmol g−1 at 570 ppm, which are record high capacities at both pressures among existing porous adsorbents. The structural stability of Mg2(dobpdc) upon exposure to wet NH3 was superior to that of the other M2(dobpdc) and the frameworks tested. Overall, these results demonstrate that Mg2(dobpdc) is a recyclable compound that exhibits significant NH3 affinity and capacity, making it a promising candidate for real-world NH3-capture applications.  相似文献   

3.
The understanding of the factors that affect the real pore‐network structure for a given bulk material due to different synthetic procedures is essential to develop the material with the best adsorption properties. In this work, we have deeply studied the influence of the crystallinity degree over the adsorption capacity on three new isostructural MOFs with the formula {[CdM(μ4‐pmdc)2(H2O)2] ? solv}n (in which, pmdc=pyrimidine‐4,6‐dicarboxylate; solv=corresponding solvent; MII=Cd ( 1 ), Mn ( 2 ), Zn ( 3 )). Compared with other methods, the solvent‐free synthesis stands as the most effective route because, apart from enabling the preparation of the heterometallic compounds 2 and 3 , it also renders the adsorbents with the highest performance, which is indeed close to the expected one derived from Grand Canonical Monte Carlo (GCMC) calculations. The structural analysis of the as‐synthesised and evacuated frameworks reveals the existence of a metal atom exposed to the pore. The accessibility of this site is limited due to its atomic environment, which is why it is considered as a pseudo‐open‐metal site. The chemical and physical characterisation confirms that this site can be modified as the metal atom is replaced in compounds 2 and 3 . To assess the effect of the metal replacement on the adsorption behaviour, an exhaustive study of CO2 experimental isotherms has been performed. The affinity of the pseudo‐open metal sites towards CO2 and the distribution of the preferred adsorption sites are discussed on the basis of DFT and GCMC calculations.  相似文献   

4.
Through a dual-ligand synthetic approach, five isoreticular primitive cubic (pcu)-type pillared-layer metal–organic frameworks (MOFs), [Zn2(dicarboxylate)2(NI-bpy-44)] ⋅ x DMF ⋅ y H2O, in which dicarboxylate=1,4-bdc ( 1 ), Br-1,4-bdc ( 2 ), NH2-1,4-bdc ( 3 ), 2,6-ndc ( 4 ), and bpdc ( 5 ), have been engineered. MOFs 1 – 5 feature twofold degrees of interpenetration and have open pores of 27.0, 33.6, 36.8, 52.5, and 62.1 %, respectively. Nitrogen adsorption isotherms of activated MOFs 1′ – 5′ at 77 K all displayed type I adsorption behavior, suggesting their microporous nature. Although 1′ and 3′ – 5′ exhibited type I adsorption isotherms of CO2 at 195 K, MOF 2′ showed a two-step gate-opening sorption isotherm of CO2. Furthermore, MOF 3′ also had a significant influence of amine functions on CO2 uptake at high temperature due to the CO2–framework interactions. MOFs 1 – 5 revealed solvent-dependent fluorescence properties; their strong blue-light emissions in aqueous suspensions were efficiently quenched by trace amounts of nitrobenzene (NB), with limits of detection of 4.54, 5.73, 1.88, 2.30, and 2.26 μm , respectively, and Stern–Volmer quenching constants (Ksv) of 2.93×103, 1.79×103, 3.78×103, 4.04×103, and 3.21×103 m −1, respectively. Of particular note, the NB-included framework, NB@ 3 , provided direct evidence of the binding sites, which showed strong host–guest π–π and hydrogen-bonding interactions beneficial for donor–acceptor electron transfer and resulting in fluorescence quenching.  相似文献   

5.
A systematic study is presented of three closely related microporous metal‐organic frameworks the pore dimensions of which vary according to the choice of 4,4′‐bipyridyl linker. The tunable linker allows exploration of the effect of increasing pore dimensions on the sorption behavior of the frameworks. The MOFs described capture CO2 under supercritical conditions and continue to sequester the gas under ambient conditions. Gas sorption isotherms for CO2 are compared with thermogravimetric data, and the CO2 molecules in the channels of the frameworks could be modeled using single‐crystal X‐ray diffraction analysis. Crystallographic data were used to construct a theoretical model based on DFT methods to calculate framework electrostatic potential maps with a view to understanding the nature of the sorbate–sorbent interactions.  相似文献   

6.
Although many monometallic active sites have been installed in metal–organic frameworks (MOFs) for catalytic reactions, there are no effective strategies to generate bimetallic catalysts in MOFs. Here we report the synthesis of a robust, efficient, and reusable MOF catalyst, MOF-NiH, by adaptively generating and stabilizing dinickel active sites using the bipyridine groups in MOF-253 with the formula of Al(OH)(2,2′-bipyridine-5,5′-dicarboxylate) for Z-selective semihydrogenation of alkynes and selective hydrogenation of C=C bonds in α,β-unsaturated aldehydes and ketones. Spectroscopic studies established the dinickel complex (bpy⋅)NiII(μ2-H)2NiII(bpy⋅) as the active catalyst. MOF-NiH efficiently catalyzed selective hydrogenation reactions with turnover numbers of up to 192 and could be used in five cycles of hydrogenation reactions without catalyst leaching or significant decrease of catalytic activities. The present work uncovers a synthetic strategy toward solution-inaccessible Earth-abundant bimetallic MOF catalysts for sustainable catalysis.  相似文献   

7.
The utility of metal–organic frameworks (MOFs) as functional materials in electronic devices has been limited to date by a lack of MOFs that display high electrical conductivity. Here, we report the synthesis of a new electrically conductive 2D MOF, Cu3(HITP)2 (HITP=2,3,6,7,10,11‐hexaiminotriphenylene), which displays a bulk conductivity of 0.2 S cm?1 (pellet, two‐point‐probe). Devices synthesized by simple drop casting of Cu3(HITP)2 dispersions function as reversible chemiresistive sensors, capable of detecting sub‐ppm levels of ammonia vapor. Comparison with the isostructural 2D MOF Ni3(HITP)2 shows that the copper sites are critical for ammonia sensing, indicating that rational design/synthesis can be used to tune the functional properties of conductive MOFs.  相似文献   

8.
A porous metal–organic framework (MOF), [Ni2(dobdc)(H2O)2]?6 H2O (Ni2(dobdc) or Ni‐MOF‐74; dobdc4?=2,5‐dioxido‐1,4‐benzenedicarboxylate) with hexagonal channels was synthesized using a microwave‐assisted solvothermal reaction. Soaking Ni2(dobdc) in sulfuric acid solutions at different pH values afforded new proton‐conducting frameworks, H+@Ni2(dobdc). At pH 1.8, the acidified MOF shows proton conductivity of 2.2×10?2 S cm?1 at 80 °C and 95 % relative humidity (RH), approaching the highest values reported for MOFs. Proton conduction occurs via the Grotthuss mechanism with a significantly low activation energy as compared to other proton‐conducting MOFs. Protonated water clusters within the pores of H+@Ni2(dobdc) play an important role in the conduction process.  相似文献   

9.
Ionic metal–organic frameworks (MOFs) are a subclass of porous materials that have the ability to incorporate different charged species in confined nanospace by ion‐exchange. To date, however, very few examples combining mesoporosity and water stability have been realized in ionic MOF chemistry. Herein, we report the rational design and synthesis of a water‐stable anionic mesoporous MOF based on uranium and featuring tbo‐type topology. The resulting tbo MOF exhibits exceptionally large open cavities (3.9 nm) exceeding those of all known anionic MOFs. By supercritical CO2 activation, a record‐high Brunauer‐Emmett‐Teller (BET) surface area (2100 m2 g?1) for actinide‐based MOFs has been obtained. Most importantly, however, this new uranium‐based MOF is water‐stable and able to absorb positively charged ions selectively over negatively charged ones, enabling the efficient separation of organic dyes and biomolecules.  相似文献   

10.
Three new metal‐organic frameworks (MOFs) were prepared by solvo(hydro)thermolysis and further characterized as framework isomers. The structural transformation from non‐porous to porous MOFs and the purity of these products can be modulated by controlling the reaction temperature. The periodic‐increased porosity observed was further confirmed by CO2 adsorption isotherms. Owing to the presence of acylamide groups in the pore walls and the flexible nature of the skeleton of these MOFs, highly selective CO2 adsorption over N2 was observed, as well as structure‐dependent periodic varieties in luminescence properties.  相似文献   

11.
Three new isostructural 3D lanthanide metal–organic frameworks (Ln‐MOFs), {H[LnL(H2O)]?2 H2O}n ( 1‐Ln ) (Ln=Eu3+, Gd3+ and Tb3+), based on infinite lanthanide‐carboxylate chains were constructed by employing an ether‐separated 5,5′‐oxydiisophthalic acid (H4L) ligand under solvothermal reaction. 1‐Eu and 1‐Tb exhibit strong red and green emission, respectively, through the antenna effect, as demonstrated through a combination of calculation and experimental results. Moreover, a series of dichromatic doped 1‐EuxTby MOFs were fabricated by introducing different concentrations of Eu3+ and Tb3+ ions, and they display an unusual variation of luminescent colors from green, yellow, orange to red. 1‐Eu with channels decorated by ether O atoms and the open metal sites displays good performance for CO2 capture and conversion between CO2 and epoxides into cyclic carbonates.  相似文献   

12.
Cationic frameworks can selectively trap anions through ion exchange, and have applications in ion chromatography and drug delivery. However, cationic frameworks are much rarer than anionic or neutral ones. Herein, we propose a concept, preemptive coordination (PC), for targeting positively charged metal–organic frameworks (P‐MOFs). PC refers to proactive blocking of metal coordination sites to preclude their occupation by neutralizing ligands such as OH?. We use 20 MOFs to show that this PC concept is an effective approach for developing P‐MOFs whose high stability, porosity, and anion‐exchange capability allow immobilization of anionic nucleotides and coenzymes, in addition to charge‐ and size‐selective capture or separation of organic dyes. The CO2 and C2H2 uptake capacity of 117.9 cm3 g?1 and 148.5 cm3 g?1, respectively, at 273 K and 1 atm, is exceptionally high among cationic framework materials.  相似文献   

13.
Metal‐organic frameworks (MOFs)‐based membranes have shown great potentials as applications in gas separation. In this work, a uniform membrane based on 2D MOF Ni3(HITP)2 (HITP=2,3,6,7,10,11‐hexaaminotriphenylene) was fabricated on ordered macroporous AAO via the filtration method. To fabricate the membrane, we obtained the Ni3(HITP)2 nanosheets as building blocks via a soft‐physical exfoliation method successfully that were confirmed by AFM and TEM. We also studied the H2, CO2 and N2 adsorption isotherms of Ni3(HITP)2 powder at room temperature, which shows Ni3(HITP)2 has high heats of adsorption for CO2 and high selectivity of CO2 over N2. Gas permeation tests indicate that the Ni3(HITP)2 membrane shows high permeance and selectivity of CO2 over N2, as well as good selectivity of H2 over N2. The ideal separation factors of CO2/N2 and H2/N2 from sing‐gas permeances are 13.6 and 7.8 respectively, with CO2 permeance of 3.15×10?6 mol?m?2?s?1?Pa?1. The membrane also showed good stability, durability and reproducibility, which are of potential interest for practical applications in the CO2 separations.  相似文献   

14.
Metal–organic frameworks (MOFs) are crystalline porous materials formed from bi‐ or multipodal organic linkers and transition‐metal nodes. Some MOFs have high structural stability, combined with large flexibility in design and post‐synthetic modification. MOFs can be photoresponsive through light absorption by the organic linker or the metal oxide nodes. Photoexcitation of the light absorbing units in MOFs often generates a ligand‐to‐metal charge‐separation state that can result in photocatalytic activity. In this Review we discuss the advantages and uniqueness that MOFs offer in photocatalysis. We present the best practices to determine photocatalytic activity in MOFs and for the deposition of co‐catalysts. In particular we give examples showing the photocatalytic activity of MOFs in H2 evolution, CO2 reduction, photooxygenation, and photoreduction.  相似文献   

15.
Acetylene separation is a very important but challenging industrial separation task. Here, through the solvothermal reaction of CuI and 5‐triazole isophthalic acid in different solvents, two metal–organic frameworks (MOFs, FJU‐21 and FJU‐22 ) with open O donor sites and controllable robustness have been obtained for acetylene separation. They contain the same paddle‐wheel {Cu2(COO2)4} nodes and metal–ligand connection modes, but with different helical chains as secondary building units (SBUs), leading to different structural robustness for the MOFs. FJU‐21 and FJU‐22 are the first examples in which the MOFs’ robustness is controlled by adjusting the helical chain SBUs. Good robustness gives the activated FJU‐22 a , which has higher surface area and gas uptakes than the flexible FJU‐21 a . Importantly, FJU‐22 a shows extraordinary separation of acetylene mixtures under ambient conditions. The separation capacity of FJU‐22 a for 50:50 C2H2/CO2 mixtures is about twice that of the high‐capacity HOF‐3, and its actual separation selectivity for C2H2/C2H4 mixtures containing 1 % acetylene is the highest among reported porous materials. Based on first‐principles calculations, the extraordinary separation performance of C2H2 for FJU‐22 a was attributed to hydrogen‐bonding interactions between the C2H2 molecules with the open O donors on the wall, which provide better recognition ability for C2H2 than other functional sites, including open metal sites and amino groups.  相似文献   

16.
Two new organic building units that contain dicarboxylate sites for their self‐assembly with paddlewheel [Cu2(CO2)4] units have been successfully developed to construct two isoreticular porous metal–organic frameworks (MOFs), ZJU‐35 and ZJU‐36, which have the same tbo topologies (Reticular Chemistry Structure Resource (RCSR) symbol) as HKUST‐1. Because the organic linkers in ZJU‐35 and ZJU‐36 are systematically enlarged, the pores in these two new porous MOFs vary from 10.8 Å in HKUST‐1 to 14.4 Å in ZJU‐35 and 16.5 Å in ZJU‐36, thus leading to their higher porosities with Brunauer–Emmett–Teller (BET) surface areas of 2899 and 4014 m2 g?1 for ZJU‐35 and ZJU‐36, respectively. High‐pressure gas‐sorption isotherms indicate that both ZJU‐35 and ZJU‐36 can take up large amounts of CH4 and CO2, and are among the few porous MOFs with the highest volumetric storage of CH4 under 60 bar and CO2 under 30 bar at room temperature. Their potential for high‐pressure swing adsorption (PSA) hydrogen purification was also preliminarily examined and compared with several reported MOFs, thus indicating the potential of ZJU‐35 and ZJU‐36 for this important application. Studies show that most of the highly porous MOFs that can volumetrically take up the greatest amount of CH4 under 60 bar and CO2 under 30 bar at room temperature are those self‐assembled from organic tetra‐ and hexacarboxylates that contain m‐benzenedicarboxylate units with the [Cu2(CO2)4] units, because this series of MOFs can have balanced porosities, suitable pores, and framework densities to optimize their volumetric gas storage. The realization of the two new organic building units for their construction of highly porous MOFs through their self‐assembly with [Cu2(CO2)4] units has provided great promise for the exploration of a large number of new tetra‐ and hexacarboxylate organic linkers based on these new organic building units in which different aromatic backbones can be readily incorporated into the frameworks to tune their porosities, pore structures, and framework densities, thus targeting some even better performing MOFs for very high gas storage and efficient gas separation under high pressure and at room temperature in the near future.  相似文献   

17.
A study on the influence of the cation coordination number, number of Lewis acid centers, concurrent existence of Lewis base sites, and structure topology on the catalytic activity of six new indium MOFs, has been carried out for multicomponent reactions (MCRs). The new indium polymeric frameworks, namely [In8(OH)6(popha)6(H2O)4]?3 H2O ( InPF‐16 ), [In(popha)(2,2′‐bipy)]?3 H2O ( InPF‐17 ), [In3(OH)3(popha)2(4,4′‐bipy)]?4 H2O ( InPF‐18 ), [In2(popha)2(4,4′‐bipy)2]?3 H2O ( InPF‐19 ), [In(OH)(Hpopha)]?0.5 (1,7‐phen) ( InPF‐20 ), and [In(popha)(1,10‐phen)]?4 H2O ( InPF‐21 ) (InPF=indium polymeric framework, H3popha=5‐(4‐carboxy‐2‐nitrophenoxy)isophthalic acid, phen=phenanthroline, bipy=bipyridine), have been hydrothermally obtained by using both conventional heating (CH) and microwave (MW) procedures. These indium frameworks show efficient Lewis acid behavior for the solvent‐free cyanosilylation of carbonyl compounds, the one pot Passerini 3‐component (P‐3CR) and the Ugi 4‐component (U‐4CR) reactions. In addition, InPF‐17 was found to be a highly reactive, recyclable, and environmentally benign catalyst, which allows the efficient synthesis of α‐aminoacyl amides. The relationship between the Lewis base/acid active site and the catalytic performance is explained by the 2D seven‐coordinated indium framework of the catalyst InPF‐17 . This study is an attempt to highlight the main structural and synthetic factors that have to be taken into account when planning a new, effective MOF‐based heterogeneous catalyst for multicomponent reactions.  相似文献   

18.
The strategy to functionalize water‐stable metal–organic frameworks (MOFs) in order to improve their CO2 uptake capacities for efficient CO2 separation remains limited and challenging. We herein present an effective approach to functionalize a prominent water‐stable MOF, UiO‐66(Zr), by a combination of optimization and metalated‐ligand exchange. In particular, by systematic optimization, we have successfully obtained UiO‐66(Zr) of the highest BET surface area reported so far (1730 m2 g?1). Moreover, it shows a hybrid Type I/IV N2 isotherm at 77 K and a mesopore size of 3.9 nm for the first time. The UiO‐66 MOF underwent a metalated‐ligand‐exchange (MLE) process to yield a series of new UiO‐66‐type MOFs, among which UiO‐66‐(COONa)2‐EX and UiO‐66‐(COOLi)4‐EX MOFs have both enhanced CO2 working capacity and IAST CO2/N2 selectivity. Our approach has thus suggested an alternative design to achieve water‐stable MOFs with high crystallinity and gas uptake for efficient CO2 separation.  相似文献   

19.
Natural gas constitutes a growing share of global primary energy due to its abundant supply and lower CO2 emission intensity compared to coal. For many natural gas reserves, CO2 contamination must be removed at the wellhead to meet pipeline specifications. Here, we demonstrate the potential of the diamine-appended metal–organic framework ee-2–Mg2(dobpdc) (ee-2 = N,N-diethylethylenediamine; dobpdc4− = 4,4′-dioxidobiphenyl-3,3′-dicarboxylate) as a next-generation CO2 capture material for high-pressure natural gas purification. Owing to a cooperative adsorption mechanism involving formation of ammonium carbamate chains, ee-2–Mg2(dobpdc) can be readily regenerated with a minimal change in temperature or pressure and maintains its CO2 capacity in the presence of water. Moreover, breakthrough experiments reveal that water enhances the CO2 capture performance of ee-2–Mg2(dobpdc) by eliminating “slip” of CO2 before full breakthrough. Spectroscopic characterization and multicomponent adsorption isobars suggest that the enhanced performance under humid conditions arises from preferential stabilization of the CO2-inserted phase in the presence of water. The favorable performance of ee-2–Mg2(dobpdc) is further demonstrated through comparison with a benchmark material for this separation, zeolite 13X, as well as extended pressure cycling. Overall, these results support continued development of ee-2–Mg2(dobpdc) as a promising adsorbent for natural gas purification.

Diamine-appended metal–organic frameworks can be optimized as adsorbents for pressure-swing purification of crude natural gas. A cooperative CO2 binding mechanism enables high CO2 swing capacities and enhanced performance under humid conditions.  相似文献   

20.
Hydrophobic metal‐organic frameworks (MOFs) not only have high water stability, but also exhibit high adsorption capacity towards organic molecules, in particular hydrocarbons. Herein we report a rare metal fluoride organic framework MFOF‐1 with high hydrophobicity, which is constructed from unprecedented fluoride‐ and sulfate‐bridged cubane‐type tetranuclear cobalt clusters. MFOF‐1 consists of three types of polyhedral cages with face‐sharing configurations, and possesses a novel (3,9)‐connected 3D+3D→3D self‐interpenetrating array or the rare pyr topology. MFOF‐1 shows high thermal stability and high stability in water and even acid/base aqueous solutions, and exhibits rather high H2 and CO2 storage capacities at ambient pressure. Remarkably, MFOF‐1 shows little adsorption of water but considerably high uptakes of methanol, n‐hexane, cyclohexane, and benzene, and exhibits a certain degree of adsorption selectivity of benzene over cyclohexane.  相似文献   

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