Research ArticleChemistry

A single-ligand ultra-microporous MOF for precombustion CO2 capture and hydrogen purification

Science Advances  18 Dec 2015:
Vol. 1, no. 11, e1500421
DOI: 10.1126/sciadv.1500421

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Abstract

Metal organic frameworks (MOFs) built from a single small ligand typically have high stability, are rigid, and have syntheses that are often simple and easily scalable. However, they are normally ultra-microporous and do not have large surface areas amenable to gas separation applications. We report an ultra-microporous (3.5 and 4.8 Å pores) Ni-(4-pyridylcarboxylate)2 with a cubic framework that exhibits exceptionally high CO2/H2 selectivities (285 for 20:80 and 230 for 40:60 mixtures at 10 bar, 40°C) and working capacities (3.95 mmol/g), making it suitable for hydrogen purification under typical precombustion CO2 capture conditions (1- to 10-bar pressure swing). It exhibits facile CO2 adsorption-desorption cycling and has CO2 self-diffusivities of ~3 × 10−9 m2/s, which is two orders higher than that of zeolite 13X and comparable to other top-performing MOFs for this application. Simulations reveal a high density of binding sites that allow for favorable CO2-CO2 interactions and large cooperative binding energies. Ultra-micropores generated by a small ligand ensures hydrolytic, hydrostatic stabilities, shelf life, and stability toward humid gas streams.

Keywords
  • Ultra-microporous
  • Metal Organic Framework
  • Hydrogen purification
  • pre-combustion CO2 capture
  • Single-ligand MOF
  • mixed-gas adsorption simulation
  • CO2 self-diffusivity
  • positron annihilation lifetime spectroscopy of MOF

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