Stability Tests

For many applications, MOFs are promising candidates. The porous framework of MOFs shall be expected (and mandatory) to be retained without any alteration over the course of a process in the practical application. In other words, stability should be considered as one of the important prerequisites for the application of MOFs. At the early stage of MOFs exploration, a lot of research focused on the design, synthesis, and application of MOFs materials. More recently, an increasing amount of work has been devoted to the study of their stability. It can be seen that the necessity and importance of stability test for MOFs.

Stability of a MOF refers to the resistance of its structure to degradation upon exposure to the operating conditions and stability test refers to the evaluation of their stability by relevant means. Alfa Chemistry has global testing abilities based on our comprehensive technical platforms and professional R&D team. We provide the most professional services and accurate experimental results for MOFs stability test.

Test Items

Depend on the considered criteria, four main categories of stabilities can be tested at Alfa Chemistry: chemical stability, water stability, thermal stability and mechanical stability. Among them, water stability is the most important part of chemical stability, which is usually discussed separately. Alfa Chemistry is able to provide the accurate test result for satisfying your requirements.

• Chemical stability: Chemical stability of MOFs refers to their ability to maintain their long-ranged ordered structure in a certain chemical environment ^[1].
• Water stability: Water stability of MOFs refers to their ability to maintain their structure in different water environments. The water stability includes stability in water vapor, stability in liquid water, stability in acid aqueous and stability in base aqueous.
• Thermal stability: Thermal stability of MOFs is usually defined as its ability to avoid irreversible changes in its chemical and physical structures upon heating to a relatively high temperature.
• Mechanical stability: Mechanical stability of MOFs is the ability to maintain its pore size and structural stiffness under mechanical loading.

Test Methods

At Alfa Chemistry, a variety of test methods are available to determine the stability of MOFs. We will provide the most suitable method according to your needs. The following is a summary of common testing methods at Alfa Chemistry：

• For chemical stability and water stability: Assessing the chemical stability and water stability of an MOF is most performed by simply comparing the powder X‐ray diffraction (PXRD) patterns of the sample before and after exposing the MOFs to a given environment. For a more precise analysis of its stability, nitrogen adsorption, infrared spectroscopy and electron microscopy (atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM)) were used as supplementary technical means to further determine if the MOF is stable or not. Nitrogen adsorption will determine the loss of porosity, which will clearly reflect any partial degradation of the MOFs framework. Infrared spectroscopy is used to determine whether there are chemical changes in the MOFs framework. Electron microscopy is used to determine changes in a particle size or morphology.
• For thermal stability: Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and variable temperature powder X-ray diffraction (VT-PXRD) are usually carried out to provide the information of thermal stability.
• For mechanical stability: Mechanical stability can be well evaluated by measuring several important parameters such as shear modulus (G), Young's modulus (E), Poisson's ratio (ν), and the bulk modulus (K).

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