Pillaring is a commonly used procedure to transform a layered crystalline i
norganic compound into a material with microporosity and mesoporosity. Firs
t, the terms layered compound, pillaring, pillaring agent and interlayer re
gion are defined, followed by the terms pillared layered solid or pillared
compound. In the second part, the standard characterization methods and pro
cedures and a systematic classification scheme are proposed.