An AlPO₄ zeotype has been prepared using the aromatic diamine 1,10-phenanthroline and some of its methylated analogues as templates. In each case the two template N atoms bind to a specific framework Al site to expand its coordination to the unusual octahedral AlO₄N₂ environment. Furthermore, using this framework-bound template, Fe atoms can be included selectively at this site in the framework by direct synthesis, as confirmed by annular dark field scanning transmission electron microscopy and Rietveld refinement. Calcination removes the organic molecules to give large pore framework solids, with BET surface areas up to 540 m² g⁻¹ and two perpendicular sets of channels that intersect to give pore space connected by 12-ring openings along all crystallographic directions.

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 1–4 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.

To gain insight into the influence of metal-organic framework (MOF) fillers and polymers on membrane performance, eight different composites were studied by combining four MOFs and two polymers. MOF materials (NH₂-MIL-53(Al), MIL-69(Al), MIL-96(Al) and ZIF-94) with various chemical functionalities, topologies, and dimensionalities of porosity were employed as fillers, and two typical polymers with different permeability-selectivity properties (6FDA-DAM and Pebax) were selected as matrices. The best-performing MOF-polymer composites were prepared by loading 25wt% of MIL-96(Al) as filler, which improved the permeability and selectivity of 6FDA-DAM to 32 and 10%, while for Pebax they were enhanced to 25 and 18%, respectively. 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.

Membrane separation for gas purification is an energy-efficient and environment-friendly technology. However, the development of high performance membranes is still a great challenge. In principle, mixed matrix membranes (MMMs) have the potential to overcome current materials limitations, but in practice there is no straightforward method to match the properties of fillers and polymers (the main components of MMMs) in such a way that the final membrane performance reflects the high performance of the microporous filler and the processability of the continuous polymer phase. This issue is especially important when high flux polymers are utilized. In this work, we demonstrate that the use of small amounts of a glassy polymer in combination with high performance PIM-1 allow for the preparation of metal–organic framework (MOF)-based MMMs with superior separation properties and low aging rates under humid conditions, meeting the commercial target for post-combustion CO₂ capture.