Issue 11, 2017

Sequential amine functionalization inducing structural transition in an aldehyde-containing zeolitic imidazolate framework: application to gas separation membranes

Abstract

A modification in the gas separation performance of zeolitic imidazolate framework (ZIF)-supported hollow fiber (HF) membranes by means of an imine-condensation functionalization reaction carried out by microfluidics is reported. The accommodation of voluminous amine molecules in the SIM-1, Zn(4-methyl-5-imidazolecarboxaldehyde)2, also known as ZIF-94, sod structure during the functionalization reaction caused the ZIF atoms to be rearranged in a less dense rho structure, with a wider pore diameter and a diminished CO2 affinity. These changes had effects on the membrane performance, resulting in an enhanced CO2 permeance while maintaining a good permeance–selectivity balance. ZIF aldehyde-containing SIM-1 membranes were earlier prepared on the inner side of polymeric P84® HF using a microfluidic approach. The SIM-1 membranes displayed very interesting results in the separation of gas mixtures of great relevance to the natural gas field. High selectivities in the separation of He/CH4 (160), H2/CH4 (136) and CO2/CH4 (38) mixtures were achieved, and these are the first SIM-1 membranes with such a high separation performance to the best of our knowledge. These SIM-1 membranes were in situ stepwise functionalized with long-chain amine solutions, namely, hexyl- and nonylamine. Microfluidics allowed the easy sequential implementation of this post-reaction step in the membrane fabrication procedure. An imine-condensation reaction took place between the aldehyde groups in the 4-methyl-5-imidazolecarboxaldehyde ligand forming SIM-1 and the corresponding amines. The extent of the reaction was analyzed by FTIR, TGA and XRD, together with the changes in the textural properties and the adsorption capacities.

Graphical abstract: Sequential amine functionalization inducing structural transition in an aldehyde-containing zeolitic imidazolate framework: application to gas separation membranes

Supplementary files

Article information

Article type
Paper
Submitted
12 Sun 2017
Accepted
15 Yan 2017
First published
15 Yan 2017

CrystEngComm, 2017,19, 1545-1554

Sequential amine functionalization inducing structural transition in an aldehyde-containing zeolitic imidazolate framework: application to gas separation membranes

F. Cacho-Bailo, M. Etxeberría-Benavides, O. Karvan, C. Téllez and J. Coronas, CrystEngComm, 2017, 19, 1545 DOI: 10.1039/C7CE00086C

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