Paper PS+PB-MoA3
Ultrathin Metal-Organic Covalent Networks by initiated Plasma Enhanced Chemical Vapor Deposition (iPECVD) for Gas Separation Membranes

Monday, October 22, 2018, 2:00 pm, Room 104A

Metal-Organic Covalent Networks (MOCN) were synthesized as ultrathin (<100 nm), defect-free and mechanically flexible layers by initiated Plasma Enhanced Chemical Vapor Deposition (iPECVD). The low substrate temperature used for iCVD allowed use of thermal sensitive porous poly[1-trimethylsilyl)-1-propene] (PTMSP) as a substrate. Uniform layers were grown over 150 nm diameter substrates and did not delaminate upon mechanical deformation. The resulting robust MOCN/PTMSP composite membranes exhibiting outstanding gas separation performance for multiple pairs of gases. Using zinc (II) meso-tetraphenyl porphphyrin (ZnTPP) as the monomer and tert-butyl peroxide as the initiator, film deposition was achieved at low plasma excitation powers. The nearly unchanged intensity of the Soret bands in the UV-vis spectra confirmed the retention of the 18 pi e- conjugation of the monomer units incorporated into the films. The gas selectivity for the separation of H₂/CH₄ or H₂/N₂ is small (<3) for either the PTMSP base membrane or for thin films of evaporated ZnTPP. However, the gas selectivity for both H₂/CH₄ or H₂/N₂ rises to >500 for the PTMSP/iPECVD ZnTPP composite membrane, exceeding the performance of commercial membranes. Ellipsometric Porosimetry and Density Functional Theory Calculations are consistent with a pore size of ~0.4 nm in the MOCN film. Additionally, iPECVD layers derived from a metal-free porphyrin and from porphyrins containing magnanese (III) and cobalt (III) will be described.