Monitoring the coordination modulator shell at MOF nanocrystals

A small angle neutron scattering (SANS) study is presented, which investigates the impact of a modulator on nucleation and growth of MOF-5 nanoparticles. Two DMF solutions, one with the secondary building unit Zn ₄O(C₆H₅COO)₆ (SBU) and one with terephthalic acid (BDC) as a linker, were mixed, and 5 min after generation of the mixture, monodentate 4-n-decylbenzoic acid was added as a modulator agent. Time-resolved SANS during the initial stages of the particle formation process offered insight into morphological transformations during the first hours. Subsequently, it could be demonstrated that a shell is formed by the modulator wrapping around the growing MOF-5 particles while directing the formation of MOF-5 nanoparticles. This has been made possible by an identification of a mixture of deuterated and hydrogenated solvent (DMF), which matches the scattering contrast of MOF-5, thus giving access to the scattering signal of the modulator.