ln the isopropylation of biphenyl (BP) over a one-dimensional fourteen-membered ring (14-MR) CIT-5 zeolite with CFI topology, the selectivities for 4,4'-diisopropylbiphenyl (4,4-DIPB) were 50-70% in the bulk and encapsulated products at moderate temperatures below 300 degrees C. However, they decreased at high temperatures such as 350 degrees C. These results mean that CIT-5 zeolites can preferentially exclude the transition state of the bulky DIPB isomers from their channels, thus resulting in the selective formation of 4,4'-DIPB. However, the isomerization of 4,4'-DIPB occurred on external and internal acid sites of the zeolite. (c) 2007 Elsevier B.V. All rights reserved.