Ordered Mesoporous Carbons via Self-Assembly of Tailored Block Copolyethers for Pore Size-Dependent Applications

Abstract

Using an organocatalytic polymerization method for the preparation of well-defined, amphiphilic block copolyethers of the type PPOn/2-PEOm-PPOn/2 ("Reverse Pluronics", Mn up to 50 000 g/mol, DM = 1.01-1.08, >100 examples), it is demonstrated that the application of these polymers as structure-directing agents (SDAs) in a standard soft-templating process delivers ordered mesoporous carbons (OMCs), whereby the resulting pore diameters are monomodal and narrowly distributed. Moreover, by the judicious choice of the SDA properties (total molar mass, ratio of n and m, and PPO block length), pore diameters in the range of 6-18 nm can be selectively addressed, notably within the same arrangement pattern (2D hexagonal, p6mm). This provides a rational, operationally simple method to tailor pore properties of otherwise uniform carbons, also significantly reducing the effort necessary to obtain systematically altered materials. Ready access to such quick screenings is assumed to be immensely useful for pore size-dependent applications from numerous disciplines such as sensing, catalysis, or energy storage and conversion. Surprisingly, it is not only found that a minimum of Mn = 13 000 g/mol is required to deliver ordered (nondistorted) materials under these conditions but also that very high-molar-mass SDAs are best suited to achieve optimum results, potentially providing an explanation for why "Reverse Pluronics"are frequently, and wrongly, thought to be per se unsuitable for the preparation of well-ordered mesoporous carbons.