A Water-Stable Anionic Metal-Organic Framework Constructed from Columnar Zinc-Adeninate Units for Highly Selective Light Hydrocarbon Separation and Efficient Separation of Organic Dyes.

Abstract

A metal-organic framework (MOF), {(Me2NH2)2[Zn6(μ4-O)(ad)4(BPDC)4]}n (JXNU-4; ad- = adeninate), with an anionic three-dimensional (3D) framework constructed from one-dimensional (1D) columnar [Zn6(ad)4(μ4-O)]n secondary building units (SBUs) and 4,4'-biphenyldicarboxylate (BPDC2-) ligand, was prepared. The anionic 3D framework has 1D square channels with an aperture of about 9.8 Å and exhibits a carboxylate-O-decorated pore environment. The microporous nature of JXNU-4 was established by the N2 adsorption data, which gives Langmuir and Brumauer-Emmett-Teller surface areas of 1800 and 1250 m2 g-1, respectively. Noticeably, JXNU-4 shows potential as a separation agent for the selective removal of propane and ethane from natural gas with high selectivities of 144 for C3H8/CH4 (5:95) and 14.6 for C2H6/CH4 (5:95), respectively. Most importantly, JXNU-4 shows an aqueous-phase adsorption of a positively charged ion of methylene blue selectively over a negatively charged ion of resorufin, which is pertinent to the anionic nature of the framework, and provides a size-exclusive sieving of methylene blue over other positively charged ions of Janus Green B and ethyl violet, which is relevant to its pore structure, enabling the efficient aqueous-phase separation of organic dyes.