In addition to hydrogen-bonding interactions, π-π stacking involving the OSDAs also contributes to the stabilization of the obtained materials. These interactions primarily occur when OSDAs with benzene rings were used, such 4-tert-butylaniline in SU-108, and can be observed between the OSDA and the framework, but also between adjacent OSDA molecules. The two crystallographically unique 4-tert-butylanilinium found in SU-108 are packed by T-shaped π-π stacking. One of the OSDAs only forms hydrogen bonds with the framework while the second OSDA interacts with the framework by π-π stacking as shown in Fig. . Although the tert-butyl group at the tail of the molecule requires more space and causes the OSDA and the ligand to not completely align, the shortest distance between the benzene ring plane of the OSDA and the ligand plane is 3.6 Å, indicating the presence of π-π stacking.