High performance mixed matrix membranes (MMMs) composed of ZIF-94 filler and 6FDA-DAM polymer

Carbon capture and storage (CCS) using membranes for the separation of CO2 holds great promise for the reduction of atmospheric CO2 emissions from fuel combustion and industrial processes. Among the different process outlines, post-combustion CO2 capture could be easily implemented in existing power plants. However, for this technology to become viable, new membrane materials have to be developed. In this article we present the development of high performance mixed matrix membranes (MMMs) composed of ZIF-94 filler and 6FDADAM polymer matrix. The CO2/N2 separation performance was evaluated by mixed gas tests (15CO2:85N2) at 25 °C and 1–4 bar transmembrane pressure difference. The CO2 membrane permeability was increased by the addition of the ZIF-94 particles, maintaining a constant CO2/N2 selectivity of ~22. The largest increase in CO2 permeability of ~ 200% was observed for 40 wt% ZIF-94 loading, reaching the highest permeability (2310 Barrer) at similar selectivity among 6FDA-DAM MMMs reported in literature. For the first time, the ZIF-94 metal organic framework crystals with particle size smaller than 500 nm were synthesized using nonhazardous solvent (tetrahydrofuran and methanol) instead of dimethylformamide (DMF) in a scalable process. Membranes were characterized by three non-invasive image techniques, i.e. SEM, AFM and nanoscale infrared imaging by scattering-type scanning near-field optical microscopy (s-SNOM). The combination of these techniques demonstrates a very good dispersion and interaction of the filler in the polymer layer, even at very high loadings.The authors acknowledge the financial support of the European Research Council under the European Union's Seventh Framework Programme (FP/2007–2013), under grant agreement no. 608490, M4CO2 project, and the Spanish Ministry of Economy and Competitiveness (national project MAT2015-65525-R). J.G. gratefully acknowledges support from the European Union Seventh Framework Programme (FP7/2007–2013), ERC Stg, Grant Agreement n. 335746, CrystEng-MOF-MMM

Improvements to the production of ZIF-94; a case study in MOF scale-up

The authors acknowledge the financial support of the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013), under grant agreement no. 608490, M4CO2 project.The ability to produce large scale quantities of MOF materials is essential for the commercialisation of these frameworks to continue. Herein we report how the production of ZIF-94 can be improved from a ∼1 g laboratory preparation to a scalable procedure allowing for large scale production of the desired framework. The synthesis of ZIF-94 was completed at room temperature, atmospheric pressure and without the use of DMF as a solvent. This method offers improvements over the current literature synthesis routes and affords a product at 18 wt% solids. To demonstrate the robustness of the derived methodology a 60 g, large scale, batch of this framework was produced which possessed a surface area of 468 m2 g−1. This large scale sample has superior CO2 uptake of 3.3 mmol g−1 at 1 bar, an improvement of 30% over literature reports.Publisher PDFPeer reviewe

High performance mixed matrix membranes (MMMs) composed of ZIF-94 filler and 6FDA-DAM polymer

Carbon capture and storage (CCS) using membranes for the separation of CO2 holds great promise for the reduction of atmospheric CO2 emissions from fuel combustion and industrial processes. Among the different process outlines, post-combustion CO2 capture could be easily implemented in existing power plants. However, for this technology to become viable, new membrane materials have to be developed. In this article we present the development of high performance mixed matrix membranes (MMMs) composed of ZIF-94 filler and 6FDA-DAM polymer matrix. The CO2/N2 separation performance was evaluated by mixed gas tests (15CO2:85N2) at 25 °C and 1 to 4 bar transmembrane pressure difference. The CO2 membrane permeability was increased by the addition of the ZIF-94 particles, maintaining a constant CO2/N2 selectivity of ~22. The largest increase in CO2 permeability of ~ 200% was observed for 40 wt% ZIF-94 loading, reaching the highest permeability (2310 Barrer) at similar selectivity among 6FDA-DAM MMMs reported in literature. For the first time, the ZIF-94 metal organic framework crystals with particle size smaller than 500 nm were synthesized using nonhazardous solvent (tetrahydrofuran and methanol) instead of dimethylformamide (DMF) in a scalable process. Membranes were characterized by three non-invasive image techniques, i.e. SEM, AFM and nanoscale infrared imaging by scattering-type scanning near-field optical microscopy (s-SNOM). The combination of these techniques demonstrates a very good dispersion and interaction of the filler in the polymer layer, even at very high loadings

Synthesis of ZIF-93/11 hybrid nanoparticles <i>via</i> post-synthetic modification of ZIF-93 and their use for H₂/CO₂ separation

The present work shows the synthesis of nano‐sized hybrid zeolitic imidazolate frameworks (ZIFs) with the rho topology based on a mixture of the linkers benzimidazole (bIm) and 4‐methyl‐5‐imidazolecarboxaldehyde (4‐m‐5‐ica). The hybrid ZIF was obtained via post‐synthetic modification of ZIF‐93 in a bIm solution. The use of different solvents, MeOH and DMAc, and reaction times led to differences in the quantity of bIm incorporated to the framework, from 7.4 to 23% according to solid‐state NMR spectroscopy. XPS analysis showed that the mixture of linkers was also present at the surface of the particles. The inclusion of bIm to the ZIF‐93 nanoparticles improved the thermal stability of the framework and also increased the hydrophobicity according to water adsorption results. N2 and CO2 adsorption experiments revealed that the hybrid material has an intermediate adsorption capacity, between those of ZIF‐93 and ZIF‐11. Finally, ZIF‐93/11 hybrid materials were applied as fillers in polybenzimidazole (PBI) mixed matrix membranes (MMMs). These MMMs were used for H2/CO2 separation (at 180 ⁰C) reaching values of 207 Barrer of H2 and a H2/CO2 selectivity of 7.7 that clearly surpassed the Robeson upper bound (corrected for this temperature)

Influence of Filler Pore Structure and Polymer on the Performance of MOF-Based Mixed-Matrix Membranes for CO 2 Capture

International audienceMembrane gas separation units are gaining increasing attention owing to their relatively low energy consumption, ease of operation and environmental aspects. Metal-organic framework (MOF)-mixed matrix membranes (MMMs) are proposed as alternative materials delivering both the promising performance benefits from embedded MOF fillers and the processing features of polymers. In order to gain insight into the influence of MOF filler and polymer on membrane performance, eight different composites are studied by combining four MOFs and two polymers. MOF materials (NH2-MIL-53(Al), MIL-69(Al), MIL-96(Al) and ZIF-94(Zn)) with various chemical functionalities, topologies, and dimensionalities of porosity were employed as fillers, while two typical polymers with different permeability-selectivity properties (6FDA-DAM and Pebax) were deliberately selected as matrices. Separation results are rationalized on the basis of thorough characterization of the main components of the composites. The observed differences in membrane performance in the separation of CO2 from N2 are explained on the basis of gas solubility, diffusivity properties and compatibility between the filler and polymer phases