Porous makes them more promising for applications
Porous materials are an important class of materials used for many applications such as gas storage, separation and catalysis. Worldwide the economic value of porous materials is estimated up to 350 billion dollars per year1,2. Porous materials possess a high surface area per gram compared to non-porous materials which makes them more promising for applications that need surfaces to interact, such as gas storage, drug delivery and catalysis3,4. A well known class of porous materials are zeolites which are crystalline porous aluminosilicates constructed by TO4 building blocks where T mostly stands for Si4+ or Al3+ cations coordinated by O2– anions5.
To date 225 structures are registered by the International Zeolite Association (IZA)6. Two of the most known zeolites are zeolite Y and ZSM-5, both zeolites are used as catalysts in the petrochemical industry7,8.Figure 1.
1: Di?erent classes of porous materials9.A breakthrough in porous materials was the discovery of Porous Coordination Polymers (PCPs), which often possess permanent porosity, even without guest molecules inside the pores10. PCPs were mentioned for the ?rst time in 1964 by Bailar et al.9,11 and this created a third class of porous materials.
Figure 1.1 shows three di?erent classes of porous materials, which are carbonbased materials (e.g.
activated carbon), inorganic materials (e.g. zeolites) and coordinated polymers (e.
g. PCPs)9. As mentioned before, in industry mostly zeolites are used due to their high thermal and chemical stability compared to other porous materials12.
With 225 structures known, the number of available zeolites is limited6,10, therefore research is performed to ?nd a material which is porous and has a thermal and chemical stability comparable to zeolites, but has a larger versatility to obtain materials with a larger range of applications. With the discovery of PCPs a lot of research has focused on these materials13, which are built up by metal-ions or metal clusters bridged by organic molecules. This gives rise to a great versatility of PCPs that can be created.
Since Yaghi et al. mentioned it for the ?rst time, PCPs are mostly called as Metal-Organic Frameworks (MOFs)14. This publication gave a boost to the research on MOFs, which is an interesting class of materials due to their high crystallinity and porosity. This resulted in high surface areas (up to