Capturing of CO₂ with solid, enzyme inspired non volatile sorbents

Goal of project:

The goal is to develop solid adsorbents for selective removal of CO₂ from flue gases emitted from energy producing or industrial plants.

Technical content:

Development of new solid materials for selective adsorption of CO₂ and a first step of conversion of CO₂.

Technical advantages:

Existing industrial scale CO₂ removal is based on chemical absorption using aqueous alkanolamine solutions. The solution based systems bears several drawbacks such as corrosion control and considerable energy need for solvent regeneration [ref.1].
The most efficient and affordable processes for CO₂ removal from flue streams will be based pressure swing adsorption (PSA) technology [ref.2]. But in order to implement PSA technology for CO₂ removal must suitable porous adsorbent be developed. The best commercially available materials are zeolite-X. Zeolite based adsorbents have a good capacity, but the interaction energy between CO₂ and adsorbent are strongly dependent on the coverage. The first fraction of CO₂ adsorbs too strong, the energy penalty for removing this fraction make the overall process to energy demanding and expensive.

R&D challenges:

For selective adsorption of CO₂ is the R&D challenge to develop a material that has the right adsorption energy. The adjustment and improvement of adsorption properties should be based on a molecular understanding of the CO₂ solid interaction and not on trial and error.
The adsorption energy should in addition be independent of the degree of coverage in order to utilize the whole adsorption capacity, and the material must be both chemically and mechanically stable.
As a further requirement, the materials should facilitate CO₂ conversion into a form that is more convenient to handle. In nature, CO₂ is first converted into carbonate, and there are several enzymes that catalyse this reaction. All of them have metal coordinated to multiple nitrogen atoms as the active centre.

Results to date (last updated October 2015):

The interaction energy between CO₂ and the UiO-66 framework are enhanced by the introduction of amine-groups attached to the linkers. Unfortunately, the introduction of the amine functionality also reduce the stability of the structure. A systematic study with mixed amine and non-functionalized linker has been performed in order to find the optimum balance between stability and CO₂ adsorption properties. This work was presented as an oral contribution at EuropaCat in Lyon September 2013 and published (Synthesis and Characterization of Amine-Functionalized Mixed-Ligand Metal-Organic Frameworks of UiO-66 Topology) By: Chavan, Sachin M.; Shearer, Greig C.; Svelle, Stian; et al.
Inorganic Chemistry, Volume: 53 Issue: 18 Pages: 9509-9515 Published: SEP 15 2014)

Measurements of CO₂ interaction with these materials are also published (Carbon Dioxide Adsorption in Amine-Functionalized Mixed-Ligand Metal-Organic Frameworks of UiO-66 Topology ) By: Jayashree Ethiraj, Dr. Elisa Albanese, Dr. Bartolomeo Civalleri, Dr. Jenny G. Vitillo, Dr. Francesca Bonino, Dr. Sachin Chavan, Greig C. Shearer, Prof. Karl Petter Lillerud, and Prof. Silvia Bordiga. CHEMSUSCHEM, DOI: 10.1002/cssc.201402694.

Theoretical investigations have shown that UiO-66-COOH could be used for the separation of CO₂ from mixtures with N2 or CH4 and that the carbocyclic group enhances the CO₂ affinity with respect to a amine functionalized structure. A sustainable preparative route for the synthesis of UiO-66-COOH (DOI: 10.1021/ja8057953) was developed. In contrast to the previously reported methods the synthetic procedure is directly transferable to industrial scale and shows very promising space time yields. This resulted in the filing of a patent recently and was presented at the MOF 2014 conference. The sustainable synthesis of further compounds based on the UiO-66-structure will be investigated together with S. Chavan (UiO) in collaboration with the group of N. Stock (University Kiel.) also employing high-throughput methods to accelerate the work flow.

The more open UiO-67 framework is used for incorporation of metals anchored to a pyridine site. The metal complexes PtCl2, PtCl4, PtBr2, PdCl2, PdBr2, NiCl2, CuCl2, IrCl4, RhCl3 and AuCl2 have all been coordinated to the framework. The platinum complexes are so far thoroughly characterized and this work was presented as an oral contribution at MOF2012 September 16-19 in Edinburgh. The findings have been published in Probing Reactive Platinum Sites in UiO-67 Zirconium Metal–Organic Frameworks by: Sigurd Øien, Giovanni Agostini, Stian Svelle, Elisa Borfecchia, Kirill A. Lomachenko, Lorenzo Mino, Erik Gallo, Silvia Bordiga, Unni Olsbye, Karl Petter Lillerud, and Carlo Lamberti, in Chemistry of materials DOI: 10.1021/cm504362j. Further work on the metal functionalized UiO-67, has shown that UiO-67-Ni is active in ethane oligomerization. Pt complexes in UiO-67-Pt can be reduced to platinum nanoparticles, without damaging the MOF structure. The resulting compound, Pt nanoparticles dispersed in UiO-67, is an active catalyst for CO₂ hydrogenation.

A fundamental understanding of the structure is important in order to understand factors that affect the stability. The paper: Detailed Structure Analysis of Atomic Positions and Defects in Zirconium Metal-Organic Frameworks By: Sigurd Øien, David Wragg, Helge Reinsch, Stian Svelle, Silvia Bordiga, Carlo Lamberti and Karl Petter Lillerud. Published in Crystal Growth & Design dx.doi.org/10.1021/cg501386j, is an important step in that towards this understanding.

Current work is focused on incorporating more advanced functionality into UiO-67, such as imines to increase the CO₂ affinity and hydrophobic groups to increase the water stability. In addition, other Zr MOFs are being screened for catalytic activity in CO₂ reduction reactions.