Baojian Shen et al .[6] have prepar

Baojian Shen et al .[6] have prepared two dealuminated Y zeolites by steaming with and without the interference of pre-desilication and have investigated how desilication creates defects in NaY crystals, and how these defects determine the mesoporosity properties.They developed mesoporosity and the unrepairable hydroxyl nests promote the coalescence of defects in their neighborhood and the homogeneous formation of mesopores throughout the zeolite crystals. They anticipate that the concept of “defect-guided mesoporosity formation” developed in the present work will be applied to the synthetic or post - synthetic preparation of other hierarchically structured materials and to the preparation of functional materials with hybrid frameworks.[6]The removal of framework Si(0Al) and Si(1Al) units occurs,which is accompanied by there-insertion of a small amount of NFAL into the ATY zeolite framework. Crystallographically, the defect left by the removal of a Si(0Al) unit is a Si-OH group (silanol nests), the well-known hydroxyl nest, as shown in (a) of Scheme 1. These vacancies can be refilled with silicon, with a consequent ultra-stabilization of the zeolite framework, and the isolation of residual defect sites left by dealumination.They propose the existence of a ‘‘unique hydroxyl nest’’ with framework-connected Al-OH as shown in (b) of Scheme 1 in the framework of the ATY zeolites. The formation of this ‘‘unique hydroxyl nest’’ may not be restricted to the one as schematically described in Scheme 1. Vacancies containing two or more framework-connected Al-OH may also be created depending on the desilication degree in the local framework.