Shaping of metal-organic framework UiO-66 using alginates: Effect of operation variables

Shaping of metal-organic frameworks into macro-structured particles for reactors and separation processes is a fundamental step in their way towards commercialization. Extrusion techniques which are used for shaping many porous materials resulted in significant reduction of surface area in many MOF materials and thus alternative techniques are required. One alternative way to shape soft materials is to use a technique coming from molecular gastronomy and biology; the calcium alginate method. For this method, a slurry of the porous material and sodium alginate is prepared and then dropwise put in contact with calcium chloride solution forming spheres. Forming particles with both suitable diffusion and mechanical properties and without significant reductions in surface area, many operating variables must be tuned and optimized. This publication presents the results obtained showing the effects of varying several process variables of the alginate method for shaping UiO-66 MOF. Characterization in terms of surface area and other surface methods, force required to break particles (crushing strength) and measurement of isotherms of carbon dioxide. With this method we have produced MOF particles with crushing strength similar to alumina or silica) and with only 10% of reduction in surface area and adsorption capacity.