Synthesis and Structure of a 22 × 12 × 12 Extra-Large Pore Zeolite ITQ-56 Determined by 3D Electron Diffraction.

Elina Kapaca,Avelino Corma,Jung Cho,José L Jordá,Xiaodong Zou,Tom Willhammar,Jiuxing Jiang,María J Díaz-Cabañas

doi:10.1021/jacs.1c02654

Abstract

A multidimensional extra-large pore germanosilicate, denoted ITQ-56, has been synthesized by using modified memantine as an organic structure-directing agent. ITQ-56 crystallizes as plate-like nanocrystals. Its structure was determined by 3D electron diffraction/MicroED. The structure of ITQ-56 contains extra-large 22-ring channels intersecting with straight 12-ring channels. ITQ-56 is the first zeolite with 22-ring pores, which is a result of ordered vacancies of double 4-ring (d4r) units in a fully connected zeolite framework. The framework density is as low as 12.4 T atoms/1000 Å3. The discovery of the ITQ-56 structure not only fills the missing member of extra-large pore zeolite with 22-ring channels but also creates a new approach of making extra-large pore zeolites by introducing ordered vacancies in zeolite frameworks.

Highlights

Zeolites are crystalline microporous materials that consist of corner-sharing tetrahedral (TO4) units (T = Si, Al, Ge, Ga, P, Be, Ga, B, etc.) and well-defined pore structures on the molecular scale
Following the idea of expanding organic structure-directing agents (OSDAs), we selected N,N,N-trimethyl-adamantammonium TMA-da+, which has been demonstrated to be an effective OSDA for the syntheses of SSZ-13,43 SSZ-23,44 and ITQ-1,45 and we identified memantine with two additional methyl groups compared with adamantamine, as a starting molecule for preparing OSDAs directed to the synthesis of extra-large pore zeolites
ITQ-56 was obtained from a hydrothermal synthesis batch Si/ Ge ratio of 2:1 using 3,5,N,N,N-pentamethyl-1-adamantammonium as an OSDA (Figure S1)

Summary

■ INTRODUCTION

The synthesis of extra-large pore zeolites has been realized via the supramolecular assembly templating (SAT) approach.[11] In this case, organic molecules have played an important role in the formation of supramolecular assemblies that act as OSDAs during zeolite synthesis Using this approach several new extralarge pore germanosilicates have been synthesized, for example, NUD-1 (18-ring),[12] NUD-2 (14-ring),[13] ITQ-37 (30ring),[14,15] NUD-5,16 and NUD-6.17 Recently, Camblor et al presented an interesting zeolite HPM-14 with an interconnected extra-large and odd small-ring (16 × 9 × 8) channel system.[18] Despite the great efforts, zeolites with extra-large pores are still rare. The structure is featured with d4r vacancies creating extra-large 22-ring channels that fill the gap of the extra-large pore channel axis

■ RESULTS AND DISCUSSION

■ CONCLUSIONS

■ REFERENCES