Joined in 2023 
82 
63 About this deal
Jean-Philippe Dacquin obtained his PhD from the Université Sciences et Technologies de Lille 1 (France) in 2008. After two postdoctoral years at the Cardiff Catalysis Institute following the University of York with Karen Wilson and Adam F. Lee, he returned to the University of Lille where he holds a position of Associate Professor. He's the administrative head of the bachelor of Chemistry and teaches courses on inorganic chemistry and analytical chemistry. His research is devoted to the preparation of solid catalysts with controlled porosity and their application in environmental catalysis. In particular, they performed a full study on the production of UiO-66 spherical microbeads. First of all, they found that introducing a continuous flow reactor before the spray-dryer is a crucial step as the application of the spray-dryer alone yielded an amorphous product, as reported by Mitsuka et al. 137 Moreover, the sole use of a continuous flow reactor without the spray-dryer gave rise to the product with a low yield (12%) as well as poor textural properties ( S BET = 708 m 2 g −1). Thus, the combination of both was required. The authors further showed that the optimal conditions for the synthesis of UiO-66 and its derivatives included an inlet temperature of 180 °C, a flow rate of 336 mL min −1 and a feed rate of 2.4 mL min −1. The chosen inlet temperature corresponds to the minimum temperature required for the complete evaporation of the solvent, DMF. The UiO-66 microbeads produced under these conditions yielded dense spherical superstructures with an average size of 4.3 ± 2.6 μm composed of individual nanoparticle aggregates ( Fig. 16d). XRD confirmed the presence of the UiO-66 structure. In terms of textural properties, the spray-dried microbeads exhibited pronounced porosity with a high S BET of 1106 m 2 g −1, which is in good agreement with that of UiO-66 produced by classical solvothermal methods (1150–1250 m 2 g −1). 139,140
Typically, MOFs are produced in polycrystalline powder form, with the size of individual crystals ranging from several tens of nanometers to a few microns. Continuous studies on synthesis optimization and product characterization have stimulated the production of MOFs on a larger scale. Thus, a number of them are now commercially available and provided by BASF (HKUST-1/Basolite C300, ZIF-8/Basolite Z1200, Fe-BTC/Basolite F300), Strem Chemicals (CAU-10, MIL-53(Al), MIL-101(Al), PCN-250(Fe), UiO-66), and others. Ligand codes: 1,3,5-BTC – benzene-1,3,5-tricarboxylic acid; 1,2,4-BTC – benzene-1,2,4-tricarboxylic acid; BDC – benzene-1,4-dicarboxylic acid; CA – citric acid; and MIM – 2-methyl imidazole. Binder codes: MSE – methoxy-siloxane ether; PVA – polyvinyl alcohol; PVC – polyvinyl chloride; KH570 – 3(trimethoxysilyl)propyl methacrylate; and MC – methyl cellulose. Plasticizer codes: MHPC – methyl hydroxyl propyl cellulose and DMF – N, N-dimethylformamide. “—” not specified. a Measured by Hg intrusion. A. Dailly and E. Poirier, Environmental Science Evaluation of an industrial pilot scale densified MOF-177 adsorbent as an on-board hydrogen storage medium, Energy Environ. Sci., 2011, 4, 3527–3534, 10.1039/C1EE01426A. For MOFs, the primary goal of using binders is to enhance the mechanical stability of the granules. For this purpose, compounds capable of creating decently strong bonds with the surfaces of MOFs are preferred as binders. As an example, this implies cohesion of MOF particles via hydrogen bonding, and therefore, compounds possessing multiple functional groups (mainly –OH) are beneficial. This includes alcohols (polyvinyl), sugars (sucrose, cellulose), esters (hydroxypropyl cellulose) and others. However, upon shaping they cannot be removed due to the limited thermal stability of MOFs.
The culinary connection
Our servers are getting hit pretty hard right now. To continue shopping, enter the characters as they are shown Some of the most celebrated and respected chefs and hospitality professionals in the world are MOF winners. But with great recognition comes great responsibility: each MOF is expected to further their profession and guide the next generation of craftsmen in their search of not only excellence but also innovation. They're also tasked with continually expanding their own professional repertoire, learning new techniques and bettering themselves despite the accolades they've already collected. Avci-Camur et al. 141 continued exploiting the spray-drying technique for the synthesis of MOFs, targeting the UiO-66 family and more specifically UiO-66-NH 2 by the combined continuous-flow spray-drying method under aqueous conditions. For this purpose, the authors used water-soluble ZrOCl 2·8H 2O and 2-aminoterephthalic acid as the metal-precursor and the ligand, respectively. In this work specific stress was given to the use of a modulator, the acetic acid. Generally, the application of monotopic acids such as hydrochloric, formic and acetic acids facilitates the formation/crystallization of the UiO-family of MOFs. 142 Accordingly, it was shown that an increase in the acid concentration caused significant changes in textural properties. Thus, the UiO-66-NH 2 prepared with 14% acetic acid in the feed solution yielded microbeads with a S BET of 840 m 2 g −1 when spray-dried at T coil = 90 °C, T in = 150 °C, flow rate = 336 mL min −1 and feed rate = 2.4 mL min −1. However, at elevated (56%) concentrations of the acid, the S BET significantly increased up to 1036 m 2 g −1 under the same operating conditions. It should be noted that a further increase (70%) in the acid content led to a partial loss in crystallinity viewed as a decrease in reflection intensities in the XRD pattern as well as a loss in S BET down to 655 m 2 g −1. This suggests a competition between the modulator and the ligand for coordination with the metal clusters and therefore subsequent structural collapse upon exceeding occupation of the clusters by the modulator. The optimal acid concentration was found to be 30%. At this value, the spray-dried UiO-66-NH 2 yielded microbeads with a size distribution of 4–10 μm ( Fig. 16e) and exhibiting the UiO-66 structure according to XRD results. Besides, the S BET value, 1261 m 2 g −1, lies in the range of non-functionalized UiO-66 made via the solvothermal route with DMF, and is much higher than that of the spray-dried UiO-66-NH 2 prepared by Garzon-Tovar et al. ( S BET = 752 m 2 g −1). 138 Finally, the same protocol was applied to the Zr-fumarate MOF. The corresponding information is given in Table 14. J. Y. Choi, R. Huang, F. J. Uribe-romo, H. K. Chae, K. S. Park, Z. Ni, A. P. Co, M. O. Keeffe and O. M. Yaghi, Exceptional chemical and thermal stability of zeolitic imidazolate frameworks, Proc. Natl. Acad. Sci. U. S. A., 2006, 103, 10186–10191, DOI: 10.1073/pnas.0602439103.
The MOF competition and its preparation are definitely in my top lifetime memories. The hours of preparation, the stress of the competition, the recognition for all the work and commitment, have alla All has changed me forever. I have pushed myself beyond what I imagined possible and it certainly contributed in making me a better professional.” continues Meilleur Ouvrier de France Chef Thomas Marie The culinary connectionIn 2014, Grande et al. 82 performed a study on the manual extrusion of Co-based UTSA-16 with emphasis on the paste composition. To form the paste, they combined polyvinyl alcohol as the binder and a water/propanol (1/1) mixture as the plasticizer. The paste was further extruded into strips using a syringe of a chosen diameter. The thus-shaped MOFs were then dried at 80 °C for 12 h. When varying the binder content, no significant loss in specific surface area with 2 wt% binder was observed. A further increase to 3 wt% PVA led to a 5% loss of SSA. Notably, the authors stated that an activation temperature lower than 120 °C was insufficient to remove the water/propanol mixture. At the same time, 2 wt% binder was found to be adequate to provide a decent crushing strength of around 20 N upon conventional compression tests, comparable to commercial zeolite 4A extrudates (12 N). For comparison, the absence of a binder resulted in a lower mechanical strength of around 7 N. Introduction Metal–Organic Frameworks (MOFs; also called Porous Coordination Polymers, PCPs) have attracted a great deal of attention since they were first described in 1995 and developed in the early 2000s. 1,2 They represent a new class of hybrid crystalline microporous materials as they are composed of metal nodes (ions or clusters) bound together by multitopic organic linkers. Such coordination allows for an eventual 1-, 2- or 3-dimensional framework. In most cases, the metal core is formed from transition metals, while the linker is often comprised of cyclic organic compounds presenting carboxylate groups or N-donors. Over the past decades, researchers from all over the world have probed a significant number of different combinations of metal precursors, organic linkers, and synthesis conditions, leading to the discovery of many new MOF structures. Nowadays, this denomination includes several thousand structures including the famous HKUST-1, 3 UiO-66, 4 ZIF-8 5 and MIL-101. 6 Y. Zhao, Z. Song, X. Li, Q. Sun, N. Cheng, S. Lawes and X. Sun, Metal organic frameworks for energy storage and conversion, Energy Storage Mater., 2016, 2, 35–62, DOI: 10.1016/j.ensm.2015.11.005.
Finally, other less-popular techniques have been successfully applied for shaping MOFs, among which have been reviewed the so-called molecular gastronomy, ice-templating (also called freeze-casting), and phase separation (also called spinodal decomposition). These three techniques presented very low impact on the physicochemical properties of the MOFs applied and are therefore worth investigating more in detail. It should be noted, however, that ice-templating and phase separation both involve the creation of a second level of porosity macrosized (>50 nm) following the replication of ice crystals and polymers, respectively.For those outside of France, the hospitality industry, or both, the initials MOF may not ring a bell, but those three letters hold an incredible amount of significance. To be a “Meilleur Ouvrier de France” or "Best Craftsman of France" as you'll soon discover, is a very prestigious title indeed. Here's how it happens. Technically, any French citizen 23 years or older who pays the 60-euro entrance fee can compete, but few have the preparation and dedication necessary to make a serious bid for the title. A particularity of the competition is the absence of podium. Indeed, the MOF title is awarded based on the average marks obtained in the tests, so there may well be several winners or none, if no one has reached the required score to become a laureate. An aqueous spray-drying synthesis of the Zn-imidazole ZIF-8 was done by Tanaka et al. 134 In a typical synthesis, an aqueous suspension containing Zn-acetate and 2-methylimidazole was spray-dried at T in = 150 °C and a feed rate of 5 mL min −1. These conditions yielded dense spherical particles with an average size of 3.9 μm as confirmed by SEM and TEM. However, the XRD results suggested the formation of an unknown phase different from that of the original ZIF-8. Moreover, the product poorly adsorbed nitrogen as revealed by N 2 sorption measurements. Notably, the authors observed the coordination of dissolved species and therefore the solution turning into a suspension right before spraying. The authors explained this phenomenon as due to the hindrance of crystallization created by acetic acid, a by-product originating from the Zn-precursor. The presence of the acid in the as-synthesized product was demonstrated by means of FTIR spectroscopy and TGA. Accordingly, during the spray-drying process, the as-released acetic acid caused a rearrangement of Zn-(2-methylimidazole) bonds, leading to the amorphization of the final product due to the incomplete coordination of the ligands around the metal. Interestingly, the presence of non-coordinated ligands was similarly evidenced by TGA. However, redispersing the spray-dried particles in an alcohol enabled the recrystallization and thus the formation of the targeted ZIF-8 framework. Interestingly, the size of the alcohol molecule influenced the size of the nanocrystals: specifically, the longer the carbon chain the larger the nanocrystals. However, the microbead size remained in the same range. Upon recrystallization, the product yielded an XRD pattern characteristic of ZIF-8 with a S BET of 1440 m 2 g −1, which is consistent with the results published elsewhere. 135 Surprisingly, once these ZIF-8 microbeads were redispersed in an alcoholic solution, they undergo a transition from dense to hollow superstructures. Hence, the recrystallization process is fed by gradually dissolving the amorphous by-product from the surface to the core of the microbeads. In 2014 Ahmed et al. 156 proposed a different method for MOF shaping based on controlled freezing. According to it, a MOF powder in suspension can be shaped into monoliths upon controlled freezing of the solvent with its subsequent elimination via freeze-drying. The authors applied this methodology to obtain Cu-based HKUST-1 monoliths. For this, the MOF precursors were dissolved in DMSO and left for 24 h at 80 °C. After that, the solution was frozen in liquid nitrogen for 1 min and placed into a freeze-dryer to sublime the solvent. This procedure yielded highly crystalline HKUST-1 monoliths as confirmed by XRD. Moreover, the specific surface area was 870 m 2 g −1 with characteristics of both micropores and mesopores, as visible from the N 2 physisorption isotherms. Additionally, as shown by Hg intrusion, the monoliths exhibited macropores with diameters around 0.4 and 10 μm. Importantly, these macropores generated upon ice-templating were oriented in one particular direction due to the orientational growth of ice crystals during freezing. Lastly, the authors showed that the size of these macropores could be varied by altering the freezing temperature. Thus, upon freezing at 5 °C the macropores were two times bigger (∼50 μm) than the macropores generated upon freezing at −80 and −20 °C (32 and 25 μm, respectively). M. Mon, R. Bruno, J. Ferrando-Soria, D. Armentano and E. Pardo, Metal–organic framework technologies for water remediation: towards a sustainable ecosystem, J. Mater. Chem. A, 2018, 6, 4912–4947, 10.1039/C8TA00264A.
Fig. 8 Comparison of the extruded 84 and pelletized 38 ZIF-8 (left); and the pelletized 47 and extruded 79 HKUST-1 (right). Numbers indicate the BET SSA upon shaping the pristine powder into extrudates and pellets.The XRD patterns of the monoliths were found to be comparable to those of their powder analogues, suggesting that the crystal structure was retained upon shaping. The intensities however experienced a certain decrease, which was attributed to the presence of PVA. Further analyses revealed pronounced textural properties for Ni(bdc)(ted) 0.5 as given by N 2 physisorption. Its monolithic form exhibited a S BET of 1325 m 2 g −1, while its powder form presented a S BET of 1802 m 2 g −1. The difference was 27%, a value which agrees well with the initial MOF content in the paste (80 wt%). The corresponding values for ZIF-7 were 16 and 40 m 2 g −1, respectively, for its powder and printed forms. Its porosity is inaccessible to N 2 and the slightly higher available surface area was attributed to the silica binder in the printed composition. Interestingly, conventional compression tests revealed an excellent mechanical stability of up to 1.7 MPa for Ni(bdc)(ted) 0.5 due to the high content of binder (20 wt%), which provided considerably strong bonding of particles. At the same time, ZIF-7 monoliths withstood compression up to 0.8 MPa, showing that silica might be less appropriate than PVA for strongly bonding MOF particles. When probed for ethane/ethylene adsorption, Ni(bdc)(ted) 0.5 monoliths showed total uptakes of 4.1 and 2.9 mmol g −1, respectively. These values were found to be proportional to the MOF content. Notably, ZIF-7 monoliths showed total uptakes of 1.8 and 2.5 mmol g −1, respectively. Both isotherms exhibited an S-shape, revealing the pore-opening feature of this MOF upon increasing pressure. Moreira et al. 52 demonstrated the reverse selectivity of UiO-66 towards liquid-phase separation of xylene isomers. Indeed, the obtained results suggested o-xylene selectivities of 1.8 and 2.4 with respect to m- and p-xylene, at 40 °C with n-heptane as the eluent. Besides, the authors showed that the selectivities were retained upon compression, meaning that no major modification of the pore network took place upon compression. Interestingly, the authors stated that at low concentrations the selectivity values of UiO-66 were comparable to the ones previously reported for MIL-53. However, the latter failed to separate m- and p-isomers unlike UiO-66. R. Bingre, B. Louis and P. Nguyen, An Overview on Zeolite Shaping Technology and Solutions to Overcome Diffusion Limitations, Catalysts, 2018, 8, 163, DOI: 10.3390/catal8040163.
Great Deal 
New Comment