Interface regulation of mixed matrix membranes by ultrathin MOF nanosheet for faster CO₂ transfer

Mixed matrix membranes (MMMs) incorporating porous materials received extensive attention for applications of gas separation, but the one shows significant high permeability and increased selectivity is rare. Here, we report a strategy of interface regulation in two groups of MMMs via formed H-bonding by a newly designed and ultrathin metal organic framework nanosheet (MOFN). The chemically stable MOFN (thickness: 5–8 nm) with lamellae of micrometre lateral dimensions was prepared from [Hf₆] cluster and tricarboxylate ligand, where the capping molecule of formic acid coordinates with Hf⁴⁺ ion as H-bonding donor toward incorporated polymers and also acts as an anisotropic regulator for MOFN growth. The well-distributed MOFN in two polymers shows sharply promoted CO₂ permeability (720 GPU and 2085 GPU), as well as enhanced separation factor, over wide pressure and temperature ranges that are suitable for CO₂ capture from natural gas. This is because the H-bonding regulated polymer-MOFN alignments lead to contractile channel and abundant porosity, validated by Raman mapping and positron annihilation lifetime spectroscopy. This work not only gives rise two candidate membranes for selective CO₂ removal from naturals gas, but also, more prospectively, deliveries a design philosophy for construction of advanced MMMs.