Particle size effects in the kinetic trapping of a structurally-locked form of a flexible metal-organic framework

Abstract

The application of metal-org. frameworks (MOFs) for gas storage, mol. sepns. and catalysis neccesitates careful consideration of the particle size and structuralisation (e.g. pelletisation, surface-anchoring) of a material. Recently, particle size has been shown to dramatically alter the phys. and structural properties of certain MOFs but overall there is limited information on how the particle size affects the properties of flexible MOFs. Here we demonstrate that the particle size of a flexible MOF, specifically the as-synthesized form of [Cu(bcppm)H2O]•S (H2bcppm = bis(4-(4-carboxyphenyl)-1H-pyrazolyl)methane, S = solvent) (1), correlates with the rate of structural reorganisation from a "kinetically-trapped" activated 3D form of this MOF to the "open" 2D form of the structure. We also outline two methods for synthetically reducing the particle size of 1 at room temp., using 0.1 M NaOH (for two reaction times: 0.5 and 16 h) and with the sodium salt of the ligand Na2bcppm, producing crystals of 85 ± 15, 280 ± 14 and 402 ± 41 nm, resp. [on SciFinder(R)]