**2. Structure of MOFs**

The design principles of reticular chemistry suggest that deconstruction of a MOF results in four levels of structure [14].


*Drug Delivery Applications of Metal-Organic Frameworks (MOFs) DOI: http://dx.doi.org/10.5772/intechopen.103684*

## **Figure 1.**

*Structure of MOF-5. (a) Primary structure showing composition: metal ion (Zn2+) and linker (terephthalic acid), (b) secondary structure: SBU, Zn4O(-COO)6, (c) tertiary structure: internal framework formed showing linking of SBUs by the terephthalic acid linker, (d) quaternary structure: overall morphology.*


**Figure 1** depicts the above four levels of MOF structure concerning MOF-5.
