Gas Separating Metal-Organic Framework Membrane Films on Large Area 3D-Printed Tubular Ceramic Scaffolds

Polycrystalline metal-organic framework (MOF) membrane films prepared on ceramic supports can separate gases with high energy efficiency. They generally exhibit very high permeance and selectivity but suffer from cost issues through the required ceramic supports. Increasing the area and reducing the ceramic component to a minimum could be a strategy to enabling neat membrane of MOFs. In a rapid prototyping approach using 3D-printed porous scaffolds with a double helical channel geometry, we dramatically increase the active membrane area-to-volume ratio. Following stereolithographic printing and de-binding of a ceramic slurry, an adapted sintering protocol was employed to sinter commercially available alumina slurries into porous scaffolds. The 3D-printed scaffolds were optimized at a porosity of 40%, with satisfying mechanical stability. Furthermore, synthetic procedures yielding omnidirectional, homogeneous coatings on the outside and inside of the tubular scaffolds were developed. Membrane films of ZIF-8 and HKUST-1 covering a huge 50 cm² membrane area were produced in this way by applying a counter-diffusion methodology. Gas separation performance was evaluated for H2, CO2, N2 and CH4, in single-gas measurements and on their binary gas mixtures.