Polymer coating assisted shaping of metal-organic framework particles into pellets with enhanced methane uptake

Shaping metal-organic framework (MOF) particles into high packing density pellets through compaction is often accompanied by loss of porosity due to mechanical damage. Instead of shaping neat MOF particles, this work presents the shaping of well-defined HKUST-1@polyimide core-shell composite particles. The HKUST-1@polyimide particles were synthesized through a reported facile one-step surface polymer coating method that can uniformly deposit polyimide onto the HKUST-1 surfaces within seconds. Our results show that the polymer coating can function not only as a sticky layer to hold the particles together in the pellet form, but also as a protective layer that effectively reduces the fracturing and collapse of MOF particles during compaction. Consequently, densely packed pellets with uniform interparticle gaps can be obtained with MOF porosity largely retained. HKUST-1@polyimide pellets exhibited 89% higher volumetric CH4 uptake capacity than the hand-packed sample and 15% higher than that of pristine HKUST-1 pellets packed under the same pressure. This coating and shaping method provides a viable and practical solution towards achieving high density MOF pellets for industrial gas storage applications. Compacting well-defined HKUST-1@polyimide core-shell particles instead of pristine HKUST-1 can result in more densely packed pellets with less structural damage, thus leading to enhanced volumetric methane storage.