3D-3D topotactic transformation in aluminophosphate molecular sieves and its implication in new zeolite structure generation

Abstract

Zeolites have unique pore structures of molecular dimensions and tunable compositions, making them ideal for shape selective catalysis and separation. However, targeted synthesis of zeolites with new pore structures and compositions remains a key challenge. Here, we propose an approach based on a unique 3D-3D topotactic transformation, which takes advantage of weak bonding in zeolites. This is inspired by the structure transformation of PST-5, a new aluminophosphate molecular sieve, to PST-6 by calcination. The structure of nano-sized PST-5 crystals is determined by 3D electron diffraction. We find that the 3D-3D topotactic transformation involves two types of building units where penta-or hexacoordinated Al is present. We apply this approach to several other zeolite systems and predict a series of new zeolite structures that would be synthetically feasible. This method provides a concept for the synthesis of targeted zeolites, especially those which may not be feasible by conventional methods.

Three-dimensional electron diffraction for porous crystalline materials: structural determination and beyond

“…3DED has also been used for ab initio structure determination of (silico)aluminophosphates such as ITQ-51, 50 PST-5, 60 PST-6, 61 PST-13 62 and PST-14. 62 PST-5 and PST-13 were synthesized using diethylamine (DEA) as the organic structure directing agent (OSDA).…”

“…A series of new synthetically feasible zeolite structures were predicted. 60 This approach could enable targeted synthesis of novel phosphate-based materials, which adds to the existing ADOR approach applicable on silicate-based zeolites.…”

On the completeness of three-dimensional electron diffraction data for structural analysis of metal–organic frameworks

“…They are based on continuous data acquisition where the goniometer continuously rotates at a constant speed and the detector records a movie of ED patterns. The rapid development of 3DED has made large impacts on structural characterization of new materials, such as zeolites, [15][16][17][18][19][20] metal oxides [21][22][23][24] and quasicrystal approximants. 25 Metal-organic frameworks (MOFs) or porous coordination polymers (PCPs) are a class of hybrid materials linking inorganic metal building units and organic ligands.…”

Zeolite Composite Nanofiber Mesh for Indoxyl Sulfate Adsorption toward Wearable Blood Purification Devices

“…Zeolite is a promising adsorbent of IS and is an inorganic substance expressed as M n+ x/n Al x Si y O 2x+2y x− •zH 2 O. It has a porous structure, and is often used as a catalyst, molecular sieve, and adsorbent [12][13][14]. Synthetic zeolites have been actively researched as an alternative to natural zeolites [15,16], as synthetic zeolites offer a uniform structure or composition, such as pore size, Si/Al ratio, and particle size, and allow for the selective adsorption of target molecules [17].…”