The “Meilleur Ouvrier de France”competition was created in France in 1924 with the objective to revive the dwindling number of traditional craftsmen in France and recognize those who represent “high qualification in the exercise of a professional activity in the craft, commercial, service, industrial or agricultural.” Fig. 1 Schematic representation of the pelletization process applied to polycrystalline MOF powder. Moreover, spray-drying allows the direct synthesis of various materials. 128 In 2002, du Fresne von Hohenesche et al. 129 successfully prepared MCM-41 spherical microbeads with a defined arrangement of macro- and mesopores with the help of a spray-dryer. Since then, the same approach has been used for preparation of other types of porous materials, 130 allowing spray-drying to be considered as a tool for simultaneous synthesis and shaping. As is evident from Table 13, both extrusion and DIW can yield shaped objects while preserving the textural properties of pristine MOFs. The loss in surface area in the case of the 3D printed objects is somewhat higher than the binder content which is due to the presence of the plasticizer. The final printed objects have a developed network of millimeter-sized channels thanks to the layer-by-layer deposition upon printing. This can significantly improve the diffusion of gas or liquid within the shaped objects. Spray-drying The spray-drying technique has been known for over a century. As the name suggests, it is used to dry powder-like materials in a continuous fashion. Compared with ovens and conveyor belts, spray-dryers allow treating several tons per hour of wet product. Over the past few decades, the application potential of spray-drying has considerably expanded and now includes the food industry, 125 the pharmaceutical industry, 126 and many others. 127

C. Perego and P. Villa, Catalyst preparation methods, Catal. Today, 1997, 34, 281–305, DOI: 10.1016/S0920-5861(96)00055-7. V. Finsy, L. Ma, L. Alaerts, D. E. De Vos, G. V. Baron and J. F. M. Denayer, Separation of CO 2 / CH 4 mixtures with the MIL-53 (Al) metal–organic framework, Microporous Mesoporous Mater., 2009, 120, 221–227, DOI: 10.1016/j.micromeso.2008.11.007. S)-2-(2′-(bis (4-(trifluoromethyl)phenyl) phosphino)biphenyl-2-yl)-4-phenyl-4,5-dihydrooxazole MOF Product 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.A mixture of PVA and PVB was used as a binder in the study by Chanut et al. 71 The authors first mixed 5 g of MOF powder with a 3 wt% polymer blend, followed by periodical spraying of ethanol for a total of 50 mL to cause primary particle agglomeration. Upon sieving, a fraction with sizes between 1.3 and 1.7 mm ( Fig. 5h) was rounded using a rolling device to achieve the final shape. Eventually, the spheres were dried at 110 °C for 12 h to remove the residual ethanol.

C. Wang, Y. V. Kaneti, Y. Bando, J. Lin, C. Liu, J. Li and Y. Yamauchi, Metal–organic framework-derived one-dimensional porous or hollow carbon-based nanofibers for energy storage and conversion, Mater. Horiz., 2018, 5, 394–407, 10.1039/C8MH00133B. Compaction itself serves as a source of reinforcement; however, sometimes the use of binders to enhance the mechanical stability of pellets is of particular interest. Binders are usually classified into organic binders such as starch, cellulose and polyvinyl alcohol (PVA) and inorganic binders such as clays, silica and graphite. 20 They facilitate bonding of individual particles by generating a link between them. As an example, it was shown that zeolites X and Y could be pelletized using bentonite as the binder, 21 and kaolinite could be employed to bind ZSM-5 zeolite crystals together. 22 In both cases there is an alteration of both the physical and chemical properties of the final materials compared to the pristine zeolites.The paste formulation is crucial and requires special attention. Indeed, mixing of the parent powder with a liquid should yield a paste with suitable rheological properties to enable extrusion. There are many aspects which define the flow behavior such as the size and shape of the powder particles, their chemical properties, etc. Overall, the paste viscosity is dictated by the liquid content and can be decreased upon increasing the total liquid/solid ratio. More viscous pastes might require higher pressures for displacement within an extruder; however, unlike pelletization, extrusion does not affect as much the compaction of the particles as they are suspended in a liquid. Besides, in some cases the flowability, plasticity, or ability of the paste to withstand deformation upon extrusion can be enhanced by adding plasticizers. These are typical organic compounds based on cellulose or polyalcohols which facilitate the formation of the overall network. Generally, they are removed from the final extrudate composition by calcination. The MOF title is really unique. It carries an important historical legacy and recognizes work approaching perfection. It is a true honor to receive recognition for one'speers and country. Today, I proudly represent and further with my best abilities the values of professional excellence, innovation and transmission.” explains Meilleur Ouvrier de France ChefChristian Segui What is the competition about? and their applications as anodes in lithium and sodium ion batteries, Coord. Chem. Rev., 2019, 388, 172–201, DOI: 10.1016/j.ccr.2019.02.029.

Interestingly, they also prepared MIL-100 pellets following the pelletization method and compared the thus formed bodies with the granules in terms of NH 3 adsorption. The latter exhibited higher adsorption capacity at 25 °C (4.4 vs. 3.6 mmol g −1), suggesting that upon pelletization, the parent powder underwent more drastic structural and textural changes as compared to granulation. This was supported by XRD and N 2 physisorption measurements.a Attrition tests were performed by rotating a cylinder containing a baffle and the shaped UiO-66-COOH at 60 rpm for 30 min. The percentage corresponds to the total mass of the fine particles – less than 425 μm – after sieving. 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 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. Fig. 9 Schematic representation of the 3D printing process via the Direct Ink Writing (DIW) method. 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.