Characterization of Metal-Organic Frameworks (MOFs)

Metal-Organic Frameworks (MOFs) are believed to be extremely important to science in the 21^st century. Formed by connecting metal clusters with organic linkers to create 3D networks, MOFs have the potential to revolutionize a wide range of fields such as carbon capture, drug delivery and fuel cells (see Figure 1(a)). Due to their modular nature, MOFs have a huge possible design space with tens of thousands of reported and millions of theoretically predicted structures. The determination of the best MOF for a particular application among the many possible candidates requires one to compare these MOFs based on certain properties.

Perhaps, the most widely used property for such a comparison is the surface area. Surface area, known to be a strong predictor of performance, is most commonly determined from adsorption isotherm measurements via the Brunauer-Emmett-Teller (BET) method. However, it has been found that the BET method doesn’t always predict surface areas accurately, especially for high surface area MOFs which tend to be the most promising for potential applications.

In our group, we are trying to develop methods that can more reliably predict surface areas for comparison between various MOFs. For instance, in our previous publication,¹ we explored a modification to the widely used BET method, called the “BET + ESW method”. The proposed BET + ESW method predicted the area more accurately than the BET method for some structures as illustrated in Figure 1(b). Having a method that can reliably predict surface areas of MOFs from their adsorption isotherms can help researchers better assess the applicability of the new materials they synthesize. This can potentially accelerate the discovery of new materials for exciting new applications.