Since their inception in the late 1990’s, metal-organic frameworks (MOFs) have dominated porous materials research. Even more recently, efforts have been dedicated towards fabricating composites of MOFs in order to compensate for some of their shortcomings, including poor stability and limited mass transfer through pores. One of the standout composites incorporates the MOF within the pores of mesoporous silica nanoparticles (MSNs). These composites have been shown to have many different benefits: from greatly increased water stability, to enhanced adsorption ability, and better catalytic activity. However, there is a widespread issue that publications lack sufficient characterization that proves the presence of MOFs within the pores of MSN, rather than in the bulk material or on the surface of the support. The common misconceptions will be defined and our thoughts as to where these errors originate will be provided. Further, a detailed pathway on how to correct these mistakes and conclusively characterize the material will be offered. Examples that have convincing characterization will be discussed, with emphasis placed on techniques that are readily available, such as x-ray diffraction (XRD), nitrogen sorption, SEM and TEM, thermal gravimetric analysis (TGA), and others. Examples that use more niche techniques will also be discussed when relevant. In order to conclusively characterize these materials, it is necessary to look at many of these techniques in tandem and do directed experiments based on what is seen in previous steps (e.g., taking % composition data obtained from TGA and using it to make controls for nitrogen sorption studies). To conclude this work, we will highlight why creating these MOF/MSN composites is a promising direction for composite materials research. We will also draw attention to the broad range of possibilities for potential applications.

Challenges and opportunities in the synthesis and characterization of MOF/mesoporous silica composite materials

ACS Spring Meeting 2021

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