(100c) Hierarchically-Structured Porous Carbon Films By Multiscale Templating and Interfacial Engineering

The promise of inorganic membranes such as carbon molecular sieves (CMS) to revolutionize continuous high-selectivity gas and liquid separations has been quelled by persistent struggles to break through commercial performance barriers associated with the well-known trade-off between permeability and selectivity. Respective synthetic challenges common to CMS and other inorganic membrane materials include the need to minimize defect-free membrane thickness while simultaneously tailoring membrane texture and function. In addition, whereas strategies exist for scaling polymeric membranes (e.g., hollow fiber spinning), the lack of corresponding strategies for facile areal scaling of inorganic membranes, commonly prepared as two-dimensional sheets, challenges their ability to meet stringent demands for industrial separations productivity. In this talk, we will describe our synthetic efforts to realize a class of ultra-thin, three-dimensionally corrugated, self-supporting carbon thin films with tunable meso- and micro-structure toward novel CMS membranes. We will describe a synergistic strategy that exploits nanoparticle (silica)-mediated continuous porous thin film formation and concomitant interstitial and interfacial confinement of polymerization and pyrolysis as a new strategy for simultaneously tuning thickness, geometry, and microstructure of selective carbon features.[1] Specifically, convective co-assembly of sacrificial silica nanoparticle templates with molecular carbon precursors results in tunable, 3D-interdigitated mesopore topologies with extensive specific surface areas.[2] Upon template sacrifice, the resulting films offer two types of independent but interdigitated pore structures contacted across ultra-thin (i.e., nanometer-scale) three-dimensionally distributed CMS pore walls. This 3D interdigitated pore structure represents a significant area-to-volume enhancement that holds promise as a platform for molecular separations. Beyond mesoscale structuring, we also find that template-mediated interfacial phenomena provide a new handle for simultaneously tuning molecular-scale structural characteristics (e.g., sp² hybridized carbon content) that ultimately impact film texture. This work aims to demonstrate how sacrificial, template-mediated hierarchical structuring may advance the viability of CMS membranes, and, more generally, may serve as a new framework for structuring other inorganic membrane materials.

References

[1] Z. Tian, M. A. Snyder*, â??Hard-templating of symmetric and asymmetric carbon thin films with three-dimensionally ordered mesoporosity,â? Langmuir, 30 (2014) 9828-9837.

[2] Z. Tian, M.A. Snyder*, â??Nanocasting of carbon films with interdigitated bimodal three-dimensionally ordered mesopores by template-replica coassembly,â? Langmuir, 30 (2014) 12411-1242