A review of adsorbate and temperature-induced zeolite framework flexibility

It has been known for over 50 years that zeolite frameworks are flexible, yet, until recently, this characteristic has not been exploited. Framework flexibility can have significant implications on the processes that utilize zeolite materials for catalysis, sorption, or, most importantly, separations. The flexibility can result from adsorption and/or temperature changes and leads to either expansion or contraction of the unit cell. These unit cell changes have particularly significant effects on zeolite membranes, enabling defects to be closed off through framework expansion and ultimately leading to membranes with much higher selectivities than as-synthesized membranes. This review provides a general background for zeolite framework flexibility and summarizes the present literature data for adsorbate and thermally induced flexibility. (C) 2016 Elsevier Inc. All rights reserved.