Coupling atomic layer deposition with supercritical fluid processing to provide a highly C₃H₆-selective ZIF-8 membrane

Zeolitic Imidazolate Framework-8 (ZIF-8) membrane is well recognized for its great capability in efficient C3H6/C3H8 separation, and their sustainable fabrication is extremely advantageous for batch production and commercial application. In this study, a solvent-free protocol was developed for sustainable production of ZIF-8 membranes with exceptional C3H6/C3H8 selectivity through combining atomic layer deposition (ALD) technique with in situ supercritical fluid (SCF) processing. Experimental results indicated that maintaining appropriate deposition number and conducting SCF processing in gas-like supercritical carbon dioxide region were crucial for obtaining ZIF-8 membranes with excellent C3H6/C3H8 selectivity (similar to 185), one of the highest among ZIF-8 membranes reported in the literature. Noteworthy, not only residual 2-methylimidazole ligands along with vented gaseous CO2 could be fully recycled and repetitively utilized, but also obsoleting ZIF-8 membranes could be effectively patched upon SCF-based treatment. The above-mentioned solvent-free protocol holds great application prospects for sustainable production of diverse high-performance metal-organic framework membranes.