Real-Time Quantifying Microdroplet Synthesis of Metal-Organic Framework Colloids Using Gas-Phase Electrophoresis.

A hyphenated electrospray-differential mobility analysis (ES-DMA) was developed for providing a high-resolution, real-time quantitative analysis on the metal-organic framework (MOF) colloids produced via the concept of microfluidic flow chemistry. Zeolitic imidazolate framework-8 was chosen as the representative MOF of the study. The results show that the physical size and number concentration of the MOF colloid were successfully characterized by the hyphenated ES-DMA during the microdroplet synthetic process, with 3 nm and 4% of measurement uncertainties, respectively. The effects of the synthetic temperature and the molar ratio of the organic linker to metal precursor were investigated, providing an opportunity for accurate control on the particle size (100-200 nm) of the microdroplet-synthesized MOF. The work demonstrates a powerful approach for the real-time quality assurance and material optimization in microdroplet synthesis of colloidal MOFs.