Comparison of gas sorption properties of neutral and anionic metal-organic frameworks prepared from the same building blocks but in different solvent systems

Abstract

Two different 3D porous metal-organic frameworks, [Zn4O(NTN)2]·10DMA·7H2O (SNU-150) and [Zn5(NTN)4(DEF)2][NH2(C2H5)2]2·8DEF·6H2O (SNU-151), are synthesized from the same metal and organic building blocks but in different solvent systems, specifically, in the absence and the presence of a small amount of acid. SNU-150 is a doubly interpenetrated neutral framework, whereas SNU-151 is a non-interpenetrated anionic framework containing diethylammonium cations in the pores. Comparisons of the N2, H2, CO2, and CH4 gas adsorption capacities as well as the CO2 adsorption selectivity over N2 and CH4 in desolvated SNU-150' (BET: 1852 m(2) g(-1)) and SNU-151' (BET: 1563 m(2) g(-1)) samples demonstrate that the charged framework is superior to the neutral framework for gas storage and gas separation, despite its smaller surface area and different framework structure.

Keywords: adsorption; carbon dioxide; cationic guests; gas separation; metal-organic frameworks.