An Underused Framework for Simpler Sample Prep?

Metal–organic frameworks (MOFs) are some of the most promising innovative materials of the moment. Here, I present my “MOF 101” and highlight how almost limitless configurations open up a wealth of opportunities to improve sample preparation.

By Victoria Samanidou

July 2018

Structure of BAF-4, with yellow and orange spheres showing the pores. Credit: Tony Boehle.

Sample preparation is typically seen as a necessary evil – and a somewhat neglected field of research. Sorptive extraction techniques, such as solid-phase extraction (SPE) and solid-phase microextraction (SPME), dominate. The evolution of these approaches is mainly driven by the design and synthesis of new materials bearing extraordinary properties – such as metal–organic frameworks (MOFs).

MOFs are crystalline materials with coordination bonds between metal clusters (for example, metal-carboxylate clusters and metal-azolate clusters), metal atoms, or rod-shaped clusters, and multidentate organic linkers with oxygen or nitrogen donors (such as carboxylates, azoles, nitriles, and so on). Within a given material, the length of the organic linker that is used in the synthesis process determines the number of available adsorption sites. Additionally, the characteristic properties of both metal ions and linkers determine the physical properties of MOF networks with regards to their porosity, pore size, and pore surface. The structural properties of the produced frameworks can be controlled by the solvent system, pH, metal-ligand ratio, and temperature (1)(2).