Highly Selective Separation of C2H2 from CO2 by a New Dichromate

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Highly Selective Separation of C2H2 from CO2 by a New DichromateBased Hybrid Ultramicroporous Material Hayley S. Scott,† Mohana Shivanna,† Alankriti Bajpai,† David G. Madden,† Kai-Jie Chen,† Tony Pham,‡ Katherine A. Forrest,‡ Adam Hogan,‡ Brian Space,‡ John J. Perry IV,† and Michael J. Zaworotko*,† †

Bernal Institute, Department of Chemical Sciences, University of Limerick, Limerick, Republic of Ireland Department of Chemistry, University of South Florida, 4202 East Fowler Avenue, Tampa, Florida 33620, United States

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S Supporting Information *

ABSTRACT: A new hybrid ultramicroporous material, [Ni(1,4-di(pyridine-2-yl)benzene)2(Cr2O7)]n (DICRO-4-Ni-i), has been prepared and structurally characterized. Pure gas sorption isotherms and molecular modeling of sorbate− sorbent interactions imply strong selectivity for C2H2 over CO2 (SAC). Dynamic gas breakthrough coupled with temperature-programmed desorption experiments were conducted on DICRO-4-Ni-i and two other porous materials reported to exhibit high SAC, TIFSIX-2-Cu-i and MIL-100(Fe), using a C2H2/CO2/He (10:5:85) gas mixture. Whereas CO2/C2H2 coadsorption by MIL-100(Fe) mitigated the purity of trapped C2H2, negligible coadsorption and high SAC were observed for DICRO-4-Ni-i and TIFSIX-2-Cu-i. KEYWORDS: ultramicroporous materials, acetylene, carbon dioxide, adsorption, separation

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INTRODUCTION Acetylene is an important chemical commodity that has utility in a variety of industrial applications.1 Common methods used for producing C2H2 introduce contaminants, including CO2, which must later be removed. C2H2 purification using energyefficient physisorptive separation is therefore a highly sought after goal.2 Recently, our group investigated an understudied class of physisorbent materials, hybrid ultramicroporous materials (HUMs),3,4 which exhibit high selectivity, including some new benchmarks for gas mixture separation performance for small polarizable gases such as C2H25,6 and CO2.6,7 We attribute the strong performance of such HUMs to two features likely to enhance sorbent−sorbate interactions: strong electrostatics thanks to inorganic anion pillars with strongly electronegative atoms at their periphery and ultramicropores (