DFT Calculated Structures and Electronic Properties of ETS-10, AM-6, and SGU-29: Structure Stabilization through Periodic Distortions

Abstract

ETS-10, AM-6, and SGU-29 are isostructural microporous transition metal silicates that contain TiO6 and VO6 quantum wires and one-dimensional (1D) arrays of CuO4 square planes, within the structures. Owing to their unique structures, these materials commonly have the ability to adsorb large amounts of CO2 from humid flue gases without interference by moisture. Because of this interesting property, a greater understanding of the local structural features of these substances is required so that superior CO2 absorbing materials can be designed. Quantum mechanical (QM) calculations would be ideal for this purpose. Previous QM calculations have been conducted only on ETS-10 and its heteroatom-substituted analogues, employing simple cluster models or restricting periodicity to one dimension. In the current study, we carried out first-principles QM calculations on ETS-10, AM-6, and SGU-29 employing their full unit cells allowing periodicity to all three dimensions. The results show that the symmetries of TiO6 and VO6 octahedron quantum wires and the CuO4 square plane arrays undergo severe distortions with periodic patterns, and as a result, the framework structures become significantly stabilized. The calculated unit cell volume decreases on going from ETS-10 to AM-6 and SGU-29. The calculated band gap energies (E g) decrease in the same order. The band structures suggest that ETS-10 is a p-type wide band gap semiconductor, AM-6 is an n-type narrow band gap semiconductor, and SGU-29 is a semimetal.

Understanding the Effect of Water on CO2 Adsorption

“…Contrary to hydrophilic aluminosilicate zeolites, such as NaX and 5A, CO 2 uptake over coppersilicate (SGU-29), a crystalline microporous material with a structure akin to AM-6 vanadosilicate and Engelhardt ETS-10 titanosilicate, 277 was found to be unaffected by moisture. 278 Computational screening of hundreds of pure silica zeolites using GCMC simulations showed that, depending on the CO 2 /H 2 O binding site separations and CO 2 −H 2 O interaction energies, humidity may promote or impede CO 2 adsorption.…”

“…Contrary to hydrophilic aluminosilicate zeolites, such as NaX and 5A, CO 2 uptake over coppersilicate (SGU-29), a crystalline microporous material with a structure akin to AM-6 vanadosilicate and Engelhardt ETS-10 titanosilicate, was found to be unaffected by moisture . Exposure of SGU-29 at 25 °C to dry (9.9% CO 2 /18.8% O 2 /N 2 ) and humid (9.6% CO 2 /18.3% O 2 /2.9% H 2 O/N 2 , 90% RH) gas mixtures led to CO 2 uptake of 2.47 and 2.43 mmol/g, respectively.…”

Mild Liquid Phase Oxidation of Benzyl Alcohol in the Presence of Microporous Framework Copper Silicates

“…In 2015, a copper silicate SGU‐29 was described as a two‐dimensional 12‐ring channel system (Figure b), possessing a very similar structure to the titanosilicate ETS‐10 . The structure of SGU‐29 comprises a one‐dimensional array of [CuO 4 ] square planar units, each unit being surrounded by four [SiO 4 ] tetrahedra; the planes of [CuO 4 ] units are arranged almost parallel to each other creating vacant space between them, where reactions may occur , . SGU‐29 was an effective catalyst for the oxidation of cyclohexane .…”

Control of the oxidation state of copper in copper silicate SGU‐29 for efficient catalytic reduction

“…[6][7][8][9][10][11] However, there are still several shortcomings in heteroatom substitution, such as the low content of hetero-transition metal elements or random locations of incorporation into the zeolite framework. The framework of zeotypes such as SGU-29, 12 ETS-10, 13 and AM-6 14 exhibit the transition metal unit as a crystalline component. Therefore, transition metal-based zeotypes are expected to overcome the disadvantages of the aforementioned transition metal zeolite composites.…”