PCN-250 under Pressure: Sequential Phase Transformation and the Implications for MOF Densification
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2017 Metal-organic frameworks (MOFs) are an emerging class of porous materials with potential applications for gas storage and separation. With industrialization, MOFs inevitably encounter processing under mechanical pressure, whereas the behaviors of MOFs under such conditions are not commonly studied. Here, we chose PCN-250, a promising candidate for methane storage, to study the impact of uniaxial mechanical pressure on the MOFs structures and properties as a model of an MOF extrusion process. A sequential phase transformation was observed and recorded by X-ray diffraction analysis, which involved N=N bond flipping and FeO bond bending. Furthermore, the effects of pressure on the CH4 adsorption capacity of PCN-250 were investigated by experiments and simulations. The PCN-250 pellet processed under optimized conditions shows an improved volumetric CH4 uptake of 21% without obvious loss of gravimetric performance. Metal-organic frameworks (MOFs) have attracted widespread attention in recent years because of their high surface area and modular nature. A plethora of MOFs have been synthesized as efficient adsorbents for H2, CH4, and CO2. However, MOFs are normally obtained as loose crystals or crystalline powders with low packing densities, presenting a major drawback from an engineering perspective. With industrialization, MOFs inevitably encounter processing under mechanical pressure, whereas the behaviors of MOFs under such conditions are not commonly studied. Here, we studied the behavior of an MOF under uniaxial pressure as a model of an MOF extrusion process. A pressure-induced sequential phase transformation was observed and the implications for MOF densification are discussed. These results shed light on the pressure-induced structural transformation and property variations, which will provide guidance for industrialization of MOF materials in the near future. Yuan et al. studied the impact of uniaxial mechanical pressure on the structure and properties of MOFs as a model of an MOF extrusion process. PCN-250, a promising candidate for methane storage, underwent sequential phase transformation upon pressure loading, which was recorded by single-crystal X-ray diffraction analysis. Furthermore, the relationship between structure transformation and property variation was revealed, which should provide guidance for industrialization of MOF in the near future.
author list (cited authors)
Yuan, S., Sun, X., Pang, J., Lollar, C., Qin, J., Perry, Z., ... Zhou, H.
complete list of authors
Yuan, Shuai||Sun, Xing||Pang, Jiandong||Lollar, Christina||Qin, Jun-Sheng||Perry, Zac||Joseph, Elizabeth||Wang, Xuan||Fang, Yu||Bosch, Matheiu||Sun, Di||Liu, Dahuan||Zhou, Hong-Cai