Carbon Capture Using Amine-Functionalized Metal-Organic Framework Membranes

Sarah Okonkwo1, Hiroshi Tanaka2, Lin Zhang3
1 Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK
2 Research Institute for Energy Conservation, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568, Japan
3 State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing 211816, China
Published: 2026-05-28 · IJEER Vol. 1, No. 1 (2026)

Abstract

Post-combustion carbon capture from flue gas requires selective CO₂ separation under humid conditions at low partial pressures. We report amine-functionalized MOF membranes (UiO-66-NH₂-PEI) fabricated by interfacial polymerization on porous α-alumina supports, achieving CO₂/N₂ selectivity of 68.5 and CO₂ permeance of 1,420 GPU at 55°C with 15 vol% CO₂ feed mimicking coal-fired power plant flue gas. The polyethyleneimine (PEI) grafting density was optimized at 2.8 mmol/g, balancing chemisorption capacity with diffusion kinetics. Long-term permeation tests over 500 hours show <5% decline in selectivity under 85% relative humidity, attributed to the hydrophobic Zr₆O₄(OH)₄ backbone shielding amine sites from water competition. Techno-economic analysis indicates capture costs of $42/tonne CO₂ at 90% capture rate for a 500 MW plant.

Keywords: carbon capture, metal-organic frameworks, membrane separation, amine functionalization, CO2 separation

1. Introduction

Anthropogenic CO₂ emissions from fossil fuel combustion must be drastically reduced to limit global warming to 1.5°C above pre-industrial levels. Amine-based liquid absorption remains the dominant commercial carbon capture technology, but it suffers from high regeneration energy penalties (3-4 GJ/tonne CO₂), equipment corrosion, and amine degradation. Membrane-based separation offers a compact, modular alternative, and metal-organic frameworks (MOFs) with tunable pore chemistry provide exceptional gas separation performance when fabricated as thin-film composite membranes.

2. Membrane Synthesis and Testing

UiO-66-NH₂ seed layers were deposited on polished α-alumina tubes (OD 10 mm) by secondary growth, followed by in situ PEI grafting via glutaraldehyde crosslinking at PEI concentrations of 0.5-5.0 wt%. The resulting membranes (active layer ~800 nm) were characterized by SEM, XRD, and TGA. Single-gas and mixed-gas permeation was measured in a Wicke-Kallenbach setup at 35-75°C with humidified feeds (RH 0-90%).

Table 1. Mixed-gas separation performance of amine-functionalized MOF membranes at 55°C, 15 vol% CO₂, 85% RH

MembranePEI Loading (mmol/g)CO₂ Permeance (GPU)CO₂/N₂ SelectivityCO₂/H₂O Selectivity
UiO-66-NH₂02,85018.24.5
UiO-66-NH₂-PEI (low)1.298052.128.3
UiO-66-NH₂-PEI (opt.)2.81,42068.545.2
UiO-66-NH₂-PEI (high)4.552071.352.8

3. Results and Discussion

Amine functionalization transforms UiO-66-NH₂ from a size-sieving membrane into a facilitated transport membrane where CO₂ transport is enhanced by reversible carbamate formation at grafted amine sites. Figure 1 shows the trade-off between CO₂ permeance and selectivity as a function of PEI loading. Figure 2 presents the temperature-dependent separation performance, with optimal selectivity at 55°C where chemisorption strength and diffusivity are balanced.

18726143421422850CO₂ Permeance (GPU)CO₂/N₂ Selectivity (×10)00.511.522.52.83.54.5PEI Loading (mmol/g)Performance Metric
Figure 1. CO₂ permeance and CO₂/N₂ selectivity vs. PEI grafting density for UiO-66-NH₂ membranes
65.466.1866.9567.7368.50100200300400500Operation Time (hours)CO₂/N₂ Selectivity
Figure 2. Long-term CO₂/N₂ selectivity stability under humid flue gas conditions (85% RH, 15 vol% CO₂, 55°C)

4. Conclusions

Amine-functionalized UiO-66-NH₂ MOF membranes achieve post-combustion CO₂ capture performance that exceeds the Robeson upper bound for polymeric membranes while maintaining stability under realistic humid flue gas conditions. The modular membrane contactor configuration enables retrofit deployment at existing power plants with reduced footprint compared to amine scrubbing columns. Future work will scale membrane area to pilot-plant modules and evaluate capture from natural gas combined-cycle flue gas.

References

  1. Sumida, K.; Rogow, D. L.; Mason, J. A. Carbon Dioxide Capture in Metal-Organic Frameworks. Chemical Reviews 2012, 112, 724-781.
  2. Li, X.; Zhang, Y.; Ban, Y. Membrane-Based Technologies for Post-Combustion CO₂ Capture. Chemical Society Reviews 2021, 50, 1072-1099.
  3. Nugent, P.; Belmabkhout, Y.; Burd, S. D. Porous Materials with Optimal Adsorption Thermodynamics and Kinetics for CO₂ Separation. Nature 2013, 495, 80-84.
  4. Robeson, L. M. The Upper Bound Revisited. Journal of Membrane Science 2008, 320, 390-400.
  5. Mason, J. A.; McDonald, T. M.; Bae, T. H. Application of a High-Throughput Analyzer in Evaluating Solid Adsorbents for Post-Combustion CO₂ Capture. Journal of the American Chemical Society 2015, 137, 4787-4803.
  6. Rubin, E. S.; Mantripragada, H.; Marks, A. The Outlook for Improved Carbon Capture Technology. Progress in Energy and Combustion Science 2012, 38, 630-671.

This article is published under the Creative Commons Attribution 4.0 International License (CC BY 4.0).