Sealing Tro•ger base/ZIF-8 mixed matrix membranes defects for improved gas separation performance

Manufacturing defect-free mixed matrix membranes (MMMs) especially with high nanoparticle concentrations exceeding 40 wt% is still an ongoing challenge. Desired performance improvements are often unfulfilled in MMMs with high filler loading because nanoparticles with increasing contents are prone to aggregating, forming non-selective cavities, and deteriorating membrane's mechanical properties. To address this key issue, our work develops MMMs using Tro center dot ger base (TB) polymer with more hydrogen bond acceptors, polydopamine (PDA), and ZIF-8 fillers. The PDA modified ZIF-8 to create TB/ZIF-8 MMMs especially with high ZIF-8 loading over 40 wt% improves membrane mechanical properties and completely seals structural defectives to demonstrate encouraging gas selectivities. Hydrogen bonding between CN:NH and CN:OH groups within TB polymers and PDA enhances ZIF-8 interactions and reduces particle agglomeration within the polymer matrix. A TB/ZIF-8@PDA MMM containing 50 wt% ZIF-8 has H2 and CO2 permeabilities of 664.1 and 277.3 Barrer. Its ideal H2/CH4 and CO2/CH4 selectivities are 37.7 and 15.5, respectively. Equal molar CO2/CH4 mixed gas tests at various pressures demonstrate strong CO2 plasticization resistance and enhanced CO2/CH4 gas selectivity over ideal selectivity within the membranes. The combination of PDA modification technique on filler surfaces and a polymer with many hydrogen bonds acceptors is not only a feasible route to fabricate high filler loading MMMs with sealed defective structures, but also demonstrates positive impacts on membrane mechanical properties.