Volume 55, Issue 47 pp. 14614-14617
Communication

Mediating Order and Modulating Porosity by Controlled Hydrolysis in a Phosphonate Monoester Metal–Organic Framework

Benjamin S. Gelfand

Benjamin S. Gelfand

Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4 Canada

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Racheal P. S. Huynh

Racheal P. S. Huynh

Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4 Canada

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Roger K. Mah

Roger K. Mah

Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4 Canada

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Prof. George K. H. Shimizu

Corresponding Author

Prof. George K. H. Shimizu

Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4 Canada

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First published: 21 October 2016
Citations: 51

Graphical Abstract

Fine tuning of porosity: Controlled in situ ester hydrolysis during metal complexation enables the formation of isostructural phosphonate monoester and phosphonate MOFs with very different gas sorption properties. By tuning of the synthetic conditions, it is possible to selectively remove some of the monoesters lining the pore to form a hydrogen phosphonate with increased affinity for CO2.

Abstract

A crystalline and permanently porous copper phosphonate monoester framework has been synthesized from a tetraaryl trigonal phosphonate monoester linker. This material has a surface area over 1000 m2 g−1, as measured by N2 sorption, the highest reported for a phosphonate-based metal–organic framework (MOF). The monoesters result in hydrophobic pore surfaces that give a low heat of adsorption for CO2 and low calculated selectivity for CO2 over N2 and CH4 in binary mixtures. By careful manipulation of synthetic conditions, it is possible to selectively remove some of the monoesters lining the pore to form a hydrogen phosphonate while giving an isomorphous structure. This increases the affinity of the framework for CO2 giving higher ambient uptake, higher heat of adsorption, and much higher calculated selectivity for CO2 over both N2 and CH4. Formation of the acid groups is noteworthy as complexation with the parent acid gives a different structure.

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