News Article | April 14, 2016
During their life, plants constantly renew themselves. They sprout new leaves in the spring and shed them in the fall. No longer needed, damaged or dead organs such as blossoms and leaves are also cast off by a process known as abscission. By doing so, plants conserve energy and prepare for the next step in their life cycle. But how does a plant know when it is the right time to get rid of unnecessary organs? Researchers from the University of Geneva (UNIGE) and the University of Oslo (UiO) now shed light on this process. It is regulated by receptor proteins located at the surface of specific cells that form a layer around the future break point. When it is time to shed an organ, a small hormone binds to this membrane receptor and, together with a helper protein, the abscission process is initiated. Their findings are now published in the journal eLife.
News Article | April 6, 2016
Optical fiber chemical sensors based on optical absorption feature high specificity, fast response, and a much longer lifetime compared to other chemical sensors, qualities that offer significant potential for application in pollution monitoring, environmental protection, and hazardous-material detection. Now by integrating metal organic framework (MOF) materials—a new class of highly porous crystalline material—with optical fibers, researchers from Victoria University and Monash University, Australia, have co-developed a novel, highly sensitive chemical sensor based on an optical fiber coated with a thin film of a specific MOF (namely, UiO-66), which could be potentially used for real-time detection of heavy organic contaminants such as herbicides or pesticides in water. In a paper published this week in the journal Optics Letters, from The Optical Society (OSA), the researchers described their work. "Metal organic frameworks (MOFs) are networks of metal atoms linked and separated by carbon-based (organic) compounds. The UiO-66 MOF we used in the experiment is made from Zirconium and is well known for the stability in water," said Stephen Collins, professor of engineering, Victoria University, Australia. "We have demonstrated for the first time that the advanced porous material MOFs can be coated onto the end-face of optical fibers to create a novel, faster and more sensitive chemical sensor potentially used for measuring heavy organic contaminants on site and in real-time." Collins said various porous adsorbents such as pyrene-labeled monomer, silica sol-gel and zeolites have been studied recently by scientists for detecting hazardous compounds. However, the low porosity and small pores of the above adsorbents limit their use in the sensing area to small molecules. That is, they cannot detect larger or heavy organic molecules (e.g. herbicides or pesticides) in water. Metal organic frameworks are about 10 times more porous than any material previously known, so they can absorb larger molecules. MOFs form as crystals and careful selection of MOF constituents can yield crystals of ultrahigh porosity and high thermal and chemical stability. To fabricate the MOF-fiber sensor, the researchers removed the polymer coating of a conventional single mode fiber several centimeters from the end and activated the fiber surface using plasma. Then, the fiber was placed in MOF liquid solution and heated at 120 degrees Celsius for 24 hours, which allowed the activated fiber surface to attract the MOF to grow on the end-face of the fiber, resulting in a MOF thin film of 17- to 22-micrometer thickness. Collins explained that the MOF-fiber sensor can be used as an in-fiber Fabry-Perot interferometer, which is a well-established method for detecting the "optical thickness" of a thin film by studying the interference signals generated by the film interfaces. As the MOF-fiber sensor absorbs more and more contaminants, the optical thickness of the MOF thin film increases accordingly, leading to a change in the interference spectra. By using the established optical model and mathematical procedure, the researchers can calculate the optical thickness of the MOF thin film from the experimentally measured interference spectra, and hence infer the concentration of contaminants in water. In the experiment, Collin's team used the MOF-fiber sensor to detect a specific contaminant in water called Rhodamine-B (RhB) dye, a bright pink dye known as Opera Rose, which is used in the textile industry and is known to be potentially carcinogenic if ingested. "Our experimental results showed a positive detection response of the MOF-fiber sensor to RhB in water down to 48 parts per million or 0.1 millimolar, which is a very promising result, demonstrating the sensor's ability to detect pollutants at a low concentration before the pollution goes worse," said Collins. He explained the high sensitivity and fast response of the MOF-fiber sensor are attributed to the MOF's ability to pre-concentrate molecules, which can be imaged as a sponge "soaking" up molecules into its pores. Additionally, the MOF sponge selectively absorbs molecules to fit into its pores and rejects unfit ones, which enhance the sensor's sensitivity and reliability. The researchers also found the sensor's absorption process of RhB dye is non-reversible, which is ideal for long-term monitoring where RhB concentrations are minimal and a marked increase in the dye's concentration would be recognized easily, said Collins. "While the non-reversible mode suits many applications, we have also developed methods of releasing absorbed molecules by shining light down the fiber, which would make the sensor re-usable," Collin said. The researchers' next step is to further explore the MOF-fiber sensor's responses to other heavy organic contaminants such as pesticides and herbicides in water. More information: M. Nazari, M. Forouzandeh, C. Divarathne, F. Sidiroglou, M. Martinez, K. Konstas, B. Muir, A. Hill, M. Duke, M. Hill and S. Collins. "UiO-66 MOF End-Face-Coated Optical Fiber in Aqueous Contaminant Detection" Optics Letters 41, 1696 – 1699. DOI: 10.1364/OL.41.001696
News Article | November 21, 2016
Do you always get "shot" playing computer games? Do you like a sore loser also blame the equipment? Actually, rather surprisingly, you might be justified. "When you experience a delayed response playing games or working on your computer it doesn't necessarily mean there is something wrong with your human responses," Kjetil Raaen points out. In his PhD work at the Department of Informatics at the University of Oslo he has studied the actual delays caused by the computer and the screen. This detection was made possible by installing an additional cable to the computer mouse and by detecting light from the screen. Consequently, you can measure the time it took after pushing the button firing the "shot" before it revealed itself as a flash across the screen. Not enough research on lag time delay -- Some combinations of computer and screen noted a lag time delay of 0.2 seconds. Most people will experience this as a delay. Additionally you will almost certainly lose the game, says Raaen. He is frustrated by the fact that there has been so little research on response time in computer equipment. "The focus has been on the internet connection. Now the time has come to look more closely at the equipment. For many years computer speed has increased tremendously. Lately, that development has been halted quite a bit. Instead we see manufacturers trying to fit more systems in to the same computer. This is really affecting the speed," says Raaen. As a result of this old computers are in many cases faster than brand new ones. What time it takes before people experience lag or delay as a problem differs a lot. 0.2 second is the average. However, some people react to delays as small as 0.05 seconds. This applies mostly to experienced gamers. He has reached these numbers through research collaboration with Ragnhild Eg -- a former PhD at Simula, who completed her PhD at the Department of Psychology/UiO and now is a colleague of Raaen at Westerdals School of communications. Raaen's PhD is collaboration between UiO, Simula and Westerdals. "The TV is oh so slow; G-sync quite good -- Are there certain types of computer equipment that are slow? And what can consumers do remedy this situation? "An increasing number of people connect their games to the TV screen. That is not a good idea; the TV is not at all built for that kind of activity -- it is super slow. The delay is on average 0.2 seconds. That is far beyond an acceptable response time." Paradoxically, he point out that a laptop can have a faster gaming response time even if they otherwise are slower and have other weaknesses as gaming computers. He strongly recommends avoiding connecting your laptop to a big screen. "The gaming experience probably becomes better on a big screen. However, the lag time and delays increases substantially compared to using the laptop by itself. Our research also shows that screens with G-sync installed are faster than traditional screens." Office, Figher jet, VR Raeen emphasizes that this isn't all about gaming: Lag time and delays during office work can make people frustrated and tired. "We are talking about delays so small that the famous hour glass doesn't pop up, but they are nonetheless frustrating when ever present." And in a Fighter Jet this kind of delay can be critical. "The problem actually materialized in a model of JAS Gripen -- there was a delay between the maneuverable controls and the trackpad. As a consequence the pilot pushed his controls harder to get a reaction. When the plain in the en reacted the fighter jet made a much steeper turn than it should," says Raaen. "And what if the same thing happens when they are dropping bombs? This is supposed to be a problem with the Lockhead Martin F-35, the type of fighter jets that the Norwegian government is currently purchasing." Additionally, there are a lot of indications suggesting that computer delays play a part in Virtual Reality. This is probably the reason why so many VR-players experiences seasickness. Increased awareness Raaen hopes that an increased awareness at computer manufacturers and game developers surrounding these issues creates a future where future gamers only have themselves to blame when they are shot or eaten by a spider. Then they cannot blame the equipment, says Raaen who himself has spent seven years as a game developer at Funcom, developing games like Anarchy Online and Pets Vs Monsters. Currently he aims to study this more closely with a combined research position at Simula and a lecturer position at the bachelor program on Game Developing at Westerdals. New tests Together with Ragnhild Eg he will test 54 students at Westerdals 165 times in different gaming situations to study more closely in what extent these delays are affecting their ability to succeed. They will also measure how the testing subjects experience the delays. Do they for examples become stressed out, frustrated or experience other traumas? Raaen also points out other things that should be put under scrutiny; for example does it matter whether the computer mouse and keyboard are wireless or not.
News Article | December 8, 2015
A team of chemical engineers at the University of Pittsburgh recently identified the two main factors for determining the optimal catalyst for turning atmospheric CO2 into liquid fuel. The results of the study, which appeared in the journal ACS Catalysis, will streamline the search for an inexpensive yet highly effective new catalyst. Imagine a power plant that takes the excess carbon dioxide (CO2) put in the atmosphere by burning fossil fuels and converts it back into fuel. Now imagine that power plant uses only a little water and the energy in sunlight to operate. The power plant wouldn't burn fossil fuels and would actually reduce the amount of CO2 in the atmosphere during the manufacturing process. For millions of years, actual plants have been using water, sunlight, and CO2 to create sugars that allow them to grow. Scientists around the globe are now adopting their energy-producing behavior. "We're trying to speed up the natural carbon cycle and make it more efficient," said Karl Johnson, the William Kepler Whiteford Professor in the Department of Chemical & Petroleum Engineering at the University of Pittsburgh and principal investigator of the study. "You don't have to waste energy on all the extra baggage it takes to grow plants, and the result is a man-made carbon cycle that produces liquid fuel." There's one catch. CO2 is a very stable molecule, and enormous amounts of energy are required to get it to react. One common way to make use of excess CO2 involves removing an oxygen atom and combining the remaining CO with H2 to create methanol. However, during this process parts of the conversion reactor need to heat as high as 1000 degrees Celsius, which can be difficult to sustain, especially when the only energy source is the sun. A catalyst can get the CO2 to react at much lower temperatures. Some researchers have been experimenting with different materials that can get the CO2 to split--even at room temperature. But these, and most, reactive catalysts already identified are too expensive to mass-produce, and fossil fuels still offer a cheap source of energy. The low price and abundance of fossil fuels prevents a lot of companies from investing in the expensive trial and error process of researching new catalysts. The study, "Screening Lewis Pair Moieties for Catalytic Hydrogenation of CO2 in Functionalized UiO-66" (DOI: 10.1021/acscatal.5b01191) provides researchers with a good idea of how they should start looking for an optimal catalyst. Johnson, along with study co-author and post-doctoral researcher Jingyun Ye at the University of Pittsburgh, examined a series of eight different functional groups of Lewis acid and base pairs (Lewis pairs for short), which are highly reactive compounds often used as catalysts. They found that the two factors qualifying a material as a good catalyst are its hydrogen adsorption energy and the Lewis pair's hardness--a measurement of the difference between its ionization potential and electron affinity. Using this framework, Johnson plans to work with experimentalists to screen for catalysts more effectively, and hopefully, bring researchers closer to creating power plants that create liquid fuel while reducing atmospheric CO2. Imagine contributing to the reduction of CO2 in the atmosphere every time you fill up your gas tank.
News Article | December 8, 2015
Imagine a power plant that takes the excess carbon dioxide (CO ) put in the atmosphere by burning fossil fuels and converts it back into fuel. Now imagine that power plant uses only a little water and the energy in sunlight to operate. The power plant wouldn't burn fossil fuels and would actually reduce the amount of CO in the atmosphere during the manufacturing process. For millions of years, actual plants have been using water, sunlight, and CO to create sugars that allow them to grow. Scientists around the globe are now adopting their energy-producing behavior. "We're trying to speed up the natural carbon cycle and make it more efficient," said Karl Johnson, the William Kepler Whiteford Professor in the Department of Chemical & Petroleum Engineering at the University of Pittsburgh and principal investigator of the study. "You don't have to waste energy on all the extra baggage it takes to grow plants, and the result is a man-made carbon cycle that produces liquid fuel." There's one catch. CO is a very stable molecule, and enormous amounts of energy are required to get it to react. One common way to make use of excess CO involves removing an oxygen atom and combining the remaining CO with H to create methanol. However, during this process parts of the conversion reactor need to heat as high as 1000 degrees Celsius, which can be difficult to sustain, especially when the only energy source is the sun. A catalyst can get the CO to react at much lower temperatures. Some researchers have been experimenting with different materials that can get the CO to split—even at room temperature. But these, and most, reactive catalysts already identified are too expensive to mass-produce, and fossil fuels still offer a cheap source of energy. The low price and abundance of fossil fuels prevents a lot of companies from investing in the expensive trial and error process of researching new catalysts. The study, "Screening Lewis Pair Moieties for Catalytic Hydrogenation of CO2 in Functionalized UiO-66" provides researchers with a good idea of how they should start looking for an optimal catalyst. Johnson, along with study co-author and post-doctoral researcher Jingyun Ye at the University of Pittsburgh, examined a series of eight different functional groups of Lewis acid and base pairs (Lewis pairs for short), which are highly reactive compounds often used as catalysts. They found that the two factors qualifying a material as a good catalyst are its hydrogen adsorption energy and the Lewis pair's hardness—a measurement of the difference between its ionization potential and electron affinity. Using this framework, Johnson plans to work with experimentalists to screen for catalysts more effectively, and hopefully, bring researchers closer to creating power plants that create liquid fuel while reducing atmospheric CO . Imagine contributing to the reduction of CO in the atmosphere every time you fill up your gas tank. Explore further: Too green to be true? Researchers develop highly effective method for converting CO2 into methanol More information: Screening Lewis Pair Moieties for Catalytic Hydrogenation of CO2 in Functionalized UiO-66, ACS Catalysis, DOI: 10.1021/acscatal.5b01191
News Article | March 8, 2016
Physical delivery of anticancer drugs in controlled anatomic locations can complement the advances being made in chemo-selective therapies. To this end, an optical fiber catheter is coated in a thin layer of metal organic framework UiO-66 and the anticancer drug 5-Fluorouracil (5-FU) is deposited within the pores. Delivery of light of appropriate wavelength through the fiber catheter is found to trigger the release of 5-FU on demand, offering a new route to localized drug administration. The system exhibits great potential with as much as 110 × 10−6 m of 5-FU delivered within 1 min from one fiber.
News Article | April 7, 2016
Researchers at UiO and NCMM have discovered that the system used by bacteria to transport magnesium is so sensitive that it can detect a pinch of magnesium salt in a swimming pool.
News Article | August 30, 2016
A UiO-66 core with various sizes acts as heterogeneous nucleation center and enables aniline polymerization under ambient conditions. The as-synthesized UiO-66@PAN possesses uniform size and excellent dispersibility in aqueous solution. UiO-66@PAN can be internalized by cancer cells via endocytosis, and indicates significant photothermal therapeutic effect in vitro, and can effectively inhibit the growth of colon cancers in vivo.
News Article | November 2, 2016
The coordinatively unsaturated metal sites (CUSs) inside MOFs can be readily tuned to adjust interactions between MOFs and reactants, to activate targeted chemical bonds in reactants and thereby to lower the reaction-energy barrier of the desired chemical transformation22. We explore this concept with MOF sandwich nanostructures that are then used as hydrogenation catalysts (Supplementary Fig. 1). The nanostructures contain a layer of platinum (Pt) nanoparticles encapsulated between a core and a shell made of MIL-101, which contains either Fe3+ or Cr3+ trimers, connected with 1,4-benzenedicarboxylate (BDC) linkers (Fig. 1a and Supplementary Note 1)19, 20, 21. All synthesized products are of uniform octahedral shape, with 2.8-nm Pt nanoparticles immobilized between the MIL-101 core and shell (Fig. 1b–l and Supplementary Figs 2–13). Catalytic performance is evaluated using five typical sandwich nanostructures: two MIL-101(Fe)@Pt@MIL-101(Fe) systems with shell thicknesses of about 9.2 nm and 22.0 nm (denoted as MIL-101(Fe)@Pt@MIL-101(Fe)9.2 and MIL-101(Fe)@Pt@MIL-101(Fe)22.0; Fig. 1b–e and Supplementary Figs 8, 9); one MIL-101(Cr)@Pt@MIL-101(Cr) with a shell thickness of around 5.1 nm (denoted as MIL-101(Cr)@Pt@MIL-101(Cr)5.1; Fig. 1f, g and Supplementary Fig. 10); and two MIL-101(Cr)@Pt@MIL-101(Fe) systems with shell thicknesses of around 2.9 nm and 8.8 nm (denoted as MIL-101(Cr)@Pt@MIL-101(Fe)2.9 and MIL-101(Cr)@Pt@MIL-101(Fe)8.8; Fig. 1h–l, Supplementary Figs 11–13 and Supplementary Note 2). All of the materials contain single crystalline MIL-101 with a face-centred-cubic (fcc) structure, and a lattice fringe of 2.6 nm that corresponds to the (222) planes of MIL-101 (ref. 19; Fig. 1c–k and Supplementary Figs 14–16). The embedded Pt nanoparticles exhibit high crystallinity, with an interplanar spacing of 0.23 nm that corresponds to the (111) planes of fcc platinum (Fig. 1e, k, insets). Table 1 summarizes the results obtained when using the sandwich MIL-101@Pt@MIL-101 nanostructures as catalysts for the selective hydrogenation of cinnamaldehyde (A) to cinnamyl alcohol (B), along with results for Pt nanoparticles, MIL-101 and MIL-101@Pt as controls (see also Fig. 1, Supplementary Figs 2–7, and Supplementary Tables 1, 2). Because the C=O and C=C groups in A are both possible hydrogenation targets, we expect a product mixture containing the targeted cinnamyl alcohol (B), as well as hydrocinnamaldehyde (C) and phenyl propanol (D). For a more meaningful evaluation of selectivity for the desired product B, we first compared the catalysts’ performances at the same conversion level (about 45%) of A. We found no noticeable hydrogenation of A by MIL-101 (Table 1, entry 9), whereas Pt nanoparticles catalyse this reaction with a turnover frequency (TOF) of 372.4 h−1 and a selectivity for B of only around 18.3% (Table 1, entry 8), consistent with density functional theory (DFT) predictions (Supplementary Fig. 17). The third controls—the MIL-101@Pt nanostructures—exhibit dramatically increased selectivity for B (Table 1, entries 6 and 7), with 86.4% for MIL-101(Fe)@Pt and 44.0% for MIL-101(Cr)@Pt. This remarkable promotion of selective hydrogenation of the C=O bond by MIL-101 is probably due to the CUSs in MIL-101 acting as Lewis acid sites that interact with the C=O bond and activate it23. A Fourier transform infrared (FTIR) survey shows an obvious redshift of the ν bond of A after mixing with MIL-101, while the ν bond remains unaltered, confirming a selective interaction between the C=O bond of A and MIL-101 (Supplementary Fig. 18). DFT calculations with consideration of spin-polarization effect—aimed at understanding the origin of the interaction between MIL-101 and A—show that the five-coordinated metal nodes in the Fe OCl(COO) H O or Cr OCl(COO) H O trimers of supertetrahedral MIL-101 cells serve as active sites that interact with the C=O group of A (Supplementary Fig. 19)19. The calculated adsorption energy of A over the Fe OCl(COO) H O and Cr OCl(COO) H O trimers is −1.26 eV and −1.01 eV, respectively (Fig. 2); that is, binding between the trimers and A through Fe–O or Cr–O interactions is thermodynamically favoured, with the interaction between A and Fe OCl(COO) H O being the stronger one (Supplementary Figs 20–22 and Supplementary Note 3). The calculated reaction energies for hydrogenation of A to B or C over MIL-101(Fe)@Pt are −2.15 eV and −1.89 eV (Fig. 2a), indicating that the formation of B (selectivity approximately 86.4%) is energetically favoured over that of C (selectivity roughly 9.6%). In the case of MIL-101(Cr)@Pt, the corresponding reaction energies for B and C formation are −0.69 eV and −0.92 eV, respectively (Fig. 2b), indicating a smaller difference in the selectivity of B (roughly 44.0%) over C (about 40.0%). These results confirm the experimental observation that the CUSs in MIL-101 preferentially interact with the C=O group (rather than the C=C group) of A and activate it, giving rise to the improved selectivity for the formation of product B. We also note that at a conversion level of 45%, TOF values are 122.1 h−1 for MIL-101(Fe)@Pt and 372.4 h−1 for MIL-101(Cr)@Pt (Table 1, entries 6 and 7), indicating that MIL-101(Cr) does not affect the catalytic activity of Pt nanoparticles whereas MIL-101(Fe) causes a considerable decrease. X-ray photoelectron spectroscopy (XPS) measurements reveal a partial transfer of electrons from the Pt nanoparticles to MIL-101(Fe)24 (Fig. 3a, b, d and Supplementary Note 4), whereas there is no obvious electron transfer between from the Pt nanoparticles to MIL-101(Cr) (Fig. 3a, c, d). This suggests the reduced electron density of Pt nanoparticles in MIL-101(Fe)@Pt as a possible cause of the decreased hydrogenation activity. This is further supported by DFT calculations showing that the negative binding energy of hydrogen atoms (ΔE ) on a platinum(111) (2 × 2) surface increases with positive charging of the platinum surface (Supplementary Fig. 23), with the resulting stronger surface binding of the hydrogen atoms reducing the catalytic activity of MIL-101(Fe)@Pt25. Guided by these observations, and given that MIL-101 possesses two characteristic pore windows (of about 1.3 nm and 1.5 nm) that are large enough to accommodate A (1.05 nm × 0.65 nm; Supplementary Table 2 and Figs 24, 25), we next explored the sandwich MIL-101@Pt@MIL-101 structure as an ideal catalyst for selective hydrogenation of A to B. Entries 1–5 in Table 1 confirm that coating with MIL-101 shells of different thicknesses considerably enhances the selectivity for B: the selectivity with MIL-101(Cr)@Pt@MIL-101(Cr)5.1 is 79.2%, while using MIL-101(Cr) or MIL-101(Fe) cores that are coated with MIL-101(Fe) shells gives selectivities that are always higher than 94%. The improved selectivities are accompanied by a decrease in TOF values, which is expected because the MIL-101 shells slow down reactant and product diffusion. Coating with MIL-101(Fe) leads to an additional decrease in catalytic activity, owing to the interfacial electron-transfer effect (Fig. 3 and Supplementary Fig. 23). Our MIL-101@Pt@MIL-101 catalysts combine exceptionally high selectivity and conversion efficiency (Table 1, entries 10–14, and Supplementary Table 3), and outperform state-of-the-art catalysts (Supplementary Table 4). MIL-101(Cr)@Pt@MIL-101(Fe)2.9, for example, exhibits excellent selectivity (95.6%) and almost full conversion (99.8%) (Supplementary Fig. 26). Moreover, reusability tests indicate that for MIL-101(Cr)@Pt@MIL-101(Fe)2.9, both the conversion efficiency of A and the selectivity for B remain almost unchanged over five successive catalytic cycles (Supplementary Figs 26–30, 31a), with the stability of the system being further verified by XRD and transmission electron microscope (TEM) measurements (Supplementary Figs 31b, 32) that show no evidence for structural or morphological differences between fresh and used catalysts. Excellent catalytic stability is also obtained with MIL-101(Fe)@Pt@MIL-101(Fe)9.2 (Supplementary Fig. 33). To further confirm that the integration of Pt nanoparticles and CUSs into a single sandwich nanostructure results in useful selective hydrogenation capabilities, we used MIL-101@Pt@MIL-101 to hydrogenate smaller-sized α,β-unsaturated aldehydes. Acrolein (0.69 nm × 0.51 nm), with no substituents on C=C bond, branched 3-methyl-2-butenal (0.79 nm × 0.60 nm), and furfural (0.81 nm × 0.64 nm), with a furan ring (see Supplementary Fig. 34 for structures), are all converted through preferential hydrogenation of the C=O group over the C=C group (Table 1, Supplementary Tables 5–7 and Supplementary Figs 35–37). Conversion efficiencies are 52.7%, 59.9% and 98.5%, respectively, with selectivities for hydrogenation of the C=O group being 97.3%, 92.5% and 99.8%. When compared with other catalysts26, 27, MIL-101(Fe)@Pt@MIL-101(Fe)22.0 also exhibits excellent selectivity towards allyl alcohol (Table 1, entries 24 and 25; Supplementary Note 5 and Supplementary Table 8). To explore the generality of the catalyst preparation method, we also synthesized28, 29, 30 the sandwich structures MOF-525(Zr)@Pt@MOF-525(Zr)26.5, MOF-74(Co)@Pt@MOF-74(Co)8.4, UiO-66(Zr)@Pt@UiO-66(Zr)11.2, and UiO-67(Zr)@Pt@UiO-67(Zr)24.1 (Supplementary Table 2 and Supplementary Figs 38–45), which catalysed the hydrogenation of A with conversion efficiencies of 35.2%, 35.0%, 90.0% and 69.4%, respectively, and selectivities towards B of 85.0%, 70.1%, 65.0% and 73.0%, respectively (Supplementary Figs 46–49 and Supplementary Table 9). Finally, as an example of a system containing different metal nanoparticles, we also prepared MIL-101(Fe)@Ru@MIL-101(Fe)8.3, which hydrogenated A with a conversion efficiency of 48.7% and a selectivity towards B of 58.5% (Supplementary Figs 50–52 and Supplementary Table 10). These results illustrate the generality of the concept of using CUSs in MOFs as a means of tuning the selectivity of the hydrogenation of α,β-unsaturated aldehydes. Moreover, using commercial Pt/C (carbon) and Pt/Fe O for the hydrogenation of A (Supplementary Figs 53, 54) resulted in conversion efficiencies of 98.1% and 54.5% and selectivities towards B of 39.9% and 84.5%, respectively (Supplementary Table 11), with the different selectivities suggesting that Fe-based supports favour the hydrogenation of C=O groups over C=C groups (although not to the extent seen with the sandwich forms of catalysts). Taken together, our observations confirm the considerable potential of MOFs as a new generation of heterogeneous catalytic supports that may prove effective when targeting important but highly challenging reactions.
News Article | December 8, 2016
Membranes with outstanding performance that are applicable in harsh environments are needed to broaden the current range of organic dehydration applications using pervaporation. Here, well-intergrown UiO-66 metal-organic framework membranes fabricated on prestructured yttria-stabilized zirconia hollow fibers are reported via controlled solvothermal synthesis. On the basis of the adsorption–diffusion mechanism, the membranes provide a very high flux of up to ca. 6.0 kg m−2 h−1 and excellent separation factor (>45 000) for separating water from i-butanol (next-generation biofuel), furfural (promising biochemical), and tetrahydrofuran (typical organic). This performance, in terms of separation factor, is one to two orders of magnitude higher than that of commercially available polymeric and silica membranes with equivalent flux. It is comparable to the performance of commercial zeolite NaA membranes. Additionally, the membrane remains robust during a pervaporation stability test (≈300 h), including exposure to harsh environments (e.g., boiling benzene, boiling water, and sulfuric acid) where some commercial membranes (e.g., zeolite NaA membranes) cannot survive.