In situ flow pair distribution function analysis to probe the assembly-disassembly-organisation-reassembly (ADOR) mechanism of zeolite IPC-2 synthesis.

Samantha E Russell,Simon M Vornholt,Susan E Henkelis,Russell E Morris,Daniel N Rainer,Karena W Chapman

doi:10.1039/d1ma00335f

Samantha E Russell, Simon M Vornholt + Show 4 more

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https://doi.org/10.1039/d1ma00335f

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Abstract

The assembly–disassembly–organisation–reassembly (ADOR) process is an important tool to access zeolite structures that are otherwise unfeasible via hydrothermal methods. In situ flow pair distribution function (PDF) analysis has been used to probe the mechanism of the disassembly and organisation steps, with the disassembly a rapid step that is often difficult to capture. Zeolite UTL was hydrolysed by 6 M hydrochloric acid, with PDF measurements used to monitor framework alterations as the reaction proceeded. The resulting disassembly mechanism shows an initial rapid removal of germanium from the germanium-rich double 4 rings (d4r), followed by silicon rearrangement and gradual silanol condensation to form IPC-2P.

Highlights

Zeolites are an important class of porous materials that are connected through TO4-tetrahedra, where T is most commonly silicon, but can be other elements such as aluminium and germanium
SEM micrographs were captured and show decisively one morphology, both the powder X-ray diffraction (PXRD) and the SEM micrographs are presented in Fig. S1 (ESI†)
The 2y position (Fig. S3, Electronic supplementary information (ESI)†) around 7.351 indicates that the product at the end of the data collection is IPC-2P, the partially connected intermediate of IPC-2, with a typical peak position around 7.51.12 The proposed final product of IPC-2P is further supported by in-house PXRD data of the recovered hydrolysis sample and the following calcination to produce IPC-2 (Fig. S4, ESI†)

Summary

Introduction

Zeolites are an important class of porous materials that are connected through TO4-tetrahedra, where T is most commonly silicon, but can be other elements such as aluminium and germanium Such zeolites are traditionally synthesised through hydrothermal methods,[1,2] though in recent times, a different method has been developed: assembly–disassembly–organization–reassembly (ADOR). This four-step process allows for the formation of new zeolites that are typically unfeasible through traditional synthesis.[3] The ADOR method begins with the assembly (A) of a parent germanosilicate (zeolite) where the germanium is preferentially located within the double 4 rings (d4r) of the 3D framework These labile germanium–oxygen linkages introduce a controlled weakness into the framework, and as such can be disassembled (D) under aqueous conditions to produce a Si-rich layered material.[4] These siliceous layers can be further organised (O) and reassembled (R) to form new zeolite frameworks that differ from the initial structure

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