An innovative strategy of internal and external coupling with multiple “locking” mechanism for the fabrication of mixed matrix membranes and their high-efficiency gas separation

The persistent rise in global carbon emissions has driven a concurrent increase of CO₂ concentrations, escalating climate change impacts and exacerbating environmental crises. Among emerging decarbonization technologies, non-thermal membrane-based gas separation has emerged as a promising approach, where mixed matrix membranes (MMMs) demonstrate particular advantages through their structure-tunable frameworks and exceptional operational stability. Zirconium-based Metal-Organic Frameworks (Zr-MOFs) demonstrate exceptional potential as nanofillers in mixed matrix membranes (MMMs) due to their precise and tunable pore architectures and molecular screening properties. However, the presence of intercrystalline defects and inadequate interfacial adhesion between the selective layer and polymer matrix compromises membrane integrity and separation efficiency. So, we developed an innovative internal-external coupling strategy combined with multi-lock self-assembly, resulting in the successful fabrication of TA@PVDF-UIO membranes. In this work, the hydroxyl groups on the TA (Tannic Acid) surface can form a stable TA-Zr-MOF composite with Zr 4 + ions through coordination bonds, constituting the first "lock". Secondly, the oxidized functional groups of PDA can interact with zirconium-based MOF (Zr-MOF) through hydrogen bonds and π-π interactions, while Zr atoms may also coordinate with PDA, forming the second "lock". Finally, by utilizing the self-assembly of ZrCl 4 and NH 2 -BDC ligands at room temperature, the secondary growth of Zr-MOF is achieved on the membrane surface, creating the third "lock", which effectively compensates for the defects in the Zr-MOF-PDA layer. This approach demonstrates remarkable enhancement in both separation selectivity and operational stability. The TA@PVDF-UIO-4 membrane achieves exceptional CO 2 permeance of 12,394 GPU with optimal selectivities of 19.8 (CO 2 /N 2 ) and 17.6 (CO 2 /CH 4 ), exceeding the so-called "2019 upper bound for polymeric membranes". Remarkably, the membrane maintains stable performance under continuous operation, owing to the multi-lock interfacial engineering strategy that creates covalent-anchored and defect-free MOF-polymer interfaces. This innovative strategy provides a new idea for designing high-performance composite membranes and offers a new method for the design of next-generation gas separation technologies and advanced membrane materials.