Polymer/MOF Composite Membrane with Individually Dispersed Filler Particles and Strong Filler-Matrix

Polymer composite membranes, also known as mixed matrix membranes, were originally developed to combine the processability of polymers and the gas selectivity of filler particles. Although metal-organic frameworks (MOFs) are getting more attention as filler particles due to their unrivaled gas separation performance, their potentials are usually underutilized due to filler aggregation and weak filler-matrix interaction. In this study, we combined polyvinylpyrrolidone functionalized UiO-66-PA nanoparticles (PVP+MOF) with poly(acrylic acid) (PAA) through H-bonding assisted layer-by-layer assembly. The resultant PAA/(PVP+MOF) bilayers feature individually dispersed fillers and strong filler-matrix interaction. Of note, we discovered that the filler-matrix interaction was extremely strong. To the best of our knowledge, this is the first polymer/MOF composite membrane whose filler-matrix interaction is stronger than the internal strength of the filler particle. Additionally, our study is the first successful attempt at creating a gas separation membrane based on layer-by-layer assembly of polymer and MOF nanoparticles. The resultant polymer composite membrane, which features individually dispersed fillers and strong filler-matrix interaction is more selective (H₂/CO₂ = 20.3) than its MOF-free counterpart (H₂/CO₂ = 12.5) and several pure-MOF membranes that were reported previously (H₂/CO₂ < 10). The technique described our report outlines a powerful new tool to control the microstructure and molecular interactions of polymer/MOF composites, which can be used in various applications, including sensing, photovoltaics, and catalysis.