Building multiple metal sites and cross-linked structures in defective Ti-MOF-based mixed matrix membranes to strengthen CO2 capture efficiency

Metal-organic frameworks (MOFs)-based mixed matrix membranes (MMMs) have demonstrated significant potential in CO 2 separation applications. However, challenges including inadequate CO 2 affinity of MOFs and insufficient compatibility at MOF-polymer interface have hindered further advancement of MMMs. Hence, this work proposes a synergistic optimization strategy involving mixed-ligand and metal modification to overcome mentioned limitations. Initially, various defect-functionalized NH 2 -MIL-125 (D X NMIL-125) fillers were synthesized by adding 5-hydroxy-o-aminobenzoic acid ligands and integrated into carboxyl-modified cPIM-1 to formulate MMMs. The resulting MMMs were then Zn (II)-modified to further strengthen gas separation capabilities. The plentiful unsaturated Ti sites in D X NMIL-125 and the introduction of Zn (II) impart exceptional CO 2 affinity to MMMs. Furthermore, they form multiple cross-linked structures with cPIM-1 via coordination, thereby improving interfacial compatibility and separation stability of MMMs. The binding energy derived from molecular simulation and CO 2 adsorption results verify that defect sites enhance CO 2 adsorption capacity of MOF. The optimal Zn@D 33 NMIL/cPIM-10 MMMs achieve a CO 2 permeability of 4312.2 Barrer and a CO 2 /N 2 selectivity of 34.8, reaching 2019 McKeown upper bound. This study presents a viable pathway for developing new-generation CO 2 selective separation MMMs.