Phase diagrams of liquid-phase mixing in multi-component metal-organic framework glasses constructed by quantitative elemental nano-tomography

Abstract

Several distinct mixing processes and resulting microstructures have recently been reported in multicomponent glasses prepared from multiple metal-organic frameworks. Here, two illustrative examples of multicomponent zeolitic imidazolate framework (ZIF) glasses, the (aTZIF-4-Co)0.5(agZIF-62)0.5 blend and the ag[(ZIF-67)0.2(ZIF-62)0.8] flux melted glass, are studied. These materials are characterized by quantitative X-ray energy dispersive spectroscopy in the scanning transmission electron microscope. By advancing a partial ionization cross section methodology using standards of arbitrary morphology, quantitative nanoscale elemental analysis throughout the glass volume is achieved. In turn, phase diagrams describing the mixing states are presented, offering mechanistic insight into the formation of the observed microstructures. Significant miscibility was observed in ag[(ZIF-67)0.2(ZIF-62)0.8]. These findings establish phase-segregation and interdiffusion as two processes in multicomponent glass formation, which explains the different outcomes observed in blending and flux melting.