In situ solid-state NMR and XRD studies of the ADOR process and the unusual structure of zeolite IPC-6

Abstract

The Assembly-Disassembly-Organisation-Reassembly (ADOR) mechanism is a recent method for preparing inorganic framework materials and, in particular, zeolites. This flexible approach has enabled the synthesis of isoreticular families of zeolites with unprecedented continuous control over porosity, and the design and preparation of materials that would have been difficult -or even impossible -to obtain using traditional hydrothermal techniques. Applying the ADOR process to a parent zeolite with the UTL framework topology, for example, has led to six previously unknown zeolites (named IPC-n with n = 2, 4, 6, 7, 9 and 10). To realize the full potential of the ADOR method, however, a further understanding of the complex mechanism at play is needed. Here, we probe the disassembly, organisation and reassembly steps of the ADOR process through a combination of in situ solid-state nuclear magnetic resonance (NMR) spectroscopy and powder Xray diffraction (PXRD) experiments. We further use the insight gained to explain the formation of the intriguing structure of zeolite IPC-6.The recently-discovered ADOR process 1-4 has proved to be effective for the preparation of new silicate and aluminosilicate zeolites, providing routes to 'unfeasible' synthesis targets with novel structural features 3 and to families of isoreticular solids whose pore size can be precisely controlled over the whole range of zeolite porosity, from small pore all the way up to extra-large pore materials. 1,4 The process comprises four distinct steps. The assembly (A) process involves the preparation of a parent zeolite with suitable chemical and topological properties for

Mechanochemically assisted hydrolysis in the ADOR process

“…the parent UTL zeolite but with loss of a s4r unit between the layers) and IPC-4 ( UTL -d4r), can be prepared in this way. In addition, the intermediate frameworks IPC-6 (combination of PCR and OKO connections, recently assigned the framework code *PCS by the IZA 3 , 20 ) and IPC-7 (combination of OKO and UTL connections) are accessible using this approach. In this vein, a study of the disassembly process using hydrochloric acid in varying concentrations was conducted in the ball mill.…”

“…12 M hydrochloric acid, HCl) or through the addition of a secondary silicon precursor such as diethoxydimethylsilane, resulting in IPC-2 ( OKO ). 13 , 18 , 19 Using 6 M hydrochloric acid directs the formation of IPC-6 ( *PCS ), 20 an intermediate between IPC-2 and IPC-4, comprised of half OKO -type and half PCR -type linkages. Furthermore, so-called “unfeasible” zeolites IPC-9 and IPC-10, containing odd-numbered rings in their framework, were produced using choline cations as intercalation agents, which changes the relative alignment of the layers before reassembly.…”

A procedure for identifying possible products in the assembly–disassembly–organization–reassembly (ADOR) synthesis of zeolites

“…These include UTL, 3,6,7 ITH, 19 ITR, 19 IWR, 19 IWW, 20 UOV 21,22 and the recently discovered SAZ-1 23 (note that a description of how the nomenclature of zeolites is derived is found below). There are several characterisation techniques that have been used to probe the ADOR mechanism and the daughter zeolites produced, including powder X-ray diffraction (PXRD) and the subsequent Rietveld refinement, 24,25 in situ and ex situ Pair Distribution Function (PDF) analysis, 24,26 solid-state NMR spectroscopy 25,27 and high resolution electron microscopy. 5,16 The ADOR process is extremely flexible, and starting from only one parent zeolite with the UTL framework topology a family of six new zeolites, named IPC-2 (OKO), IPC-4 (PCR), IPC-6 (*PCS), IPC-7, IPC-9 and IPC-10, can be prepared.…”

Synthesis and Post‐Synthesis Transformation of Germanosilicate Zeolites

“…UTL)a nd its derivative, which contain only oxygen bridges as interlayer connecting units (PCR,F igure 1). [62] Other techniques,s uch as "inverse sigma transformation" [31] or "topotactic conversion", [63] recently applied to germanosilicates,a re based on similar principles and individual steps.…”