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 can be a strategy to enabling neat membranes of MOFs. In a rapid prototyping approach using 3D-printed porous scaffolds with a double-helical channel geometry, an increased active membrane area-to-volume ratio is shown. Following stereolithographic printing and debinding of a ceramic slurry, an adapted sintering protocol is employed to sinter commercially available alumina slurries into porous scaffolds. The 3D-printed scaffolds are 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 are developed. Membrane films of zeolitic imidazolate framework 8 and Hong Kong University of Science and Technology 1 covering a huge 50 cm2 membrane area are produced in this way by applying a counter-diffusion methodology. Gas-separation performance is evaluated for H2, CO2, N2, and CH4, in single-gas measurements and on their binary-gas mixtures.