One-Pot Synthesis of Hierarchically Macro- and Mesoporous Carbon Materials with Graded Porosity

Abstract

Hierarchically porous materials are becoming increasingly important in catalysis, separation, and energy applications due to their advantageous diffusion and flux properties. Here we present the synthesis of hierarchically macro-and mesoporous carbon materials with graded porosity from a one-pot fabrication route. Organic−polymeric hybrids of a carbon precursor and poly(isoprene)-block-poly(styrene)-block-poly(4-vinylpyridine) with graded porosity are obtained via coassembly and nonsolventinduced phase separation. The membranes were carbonized at temperatures as high as 1100°C with simultaneous decomposition of the block copolymer. The carbon materials show an open nanoporous top surface with narrow pore-size distribution that opens up into a graded macroporous support with increasing macropore size along the film normal and mesoporous walls, providing for highly accessible porosity with a large surface area of over 500 m 2 g −1 . Further, we expand the direct synthesis process to form well-dispersed metal nanoparticles (such as nickel and platinum) on the graded, hierarchically porous carbon materials. Our one-pot synthesis offers a facile approach to graded macroand mesoporous carbons. M esoporous materials have been used for a wide range of applications including biomedical implants, water filtration, and energy devices, due to their high surface areas and pore volumes. In particular, mesoporous inorganic materials such as carbon, metal, and metal oxide materials have been employed for energy conversion and storage applications, as well as catalysis and separation. 1−9 In order to increase the accessibility of mesoporous materials and to promote diffusion and material flux for both gases and liquids, hierarchical meso-and macroporosity has been demonstrated to be advantageous. Furthermore, graded macroporosity featuring a continuous increase in pore size along at least one direction can combine high material flux with good separation resolution in membrane applications. 10,11 Graded porosity has also shown promise in minimizing mass transport resistance to either liquids or gases as well as increasing catalyst utilization and power density in fuel cell electrode materials. 12,13 Combining the synthesis of inorganic materials with polymer fabrication techniques in soft-or hard-templating processes opens the door to facile scalability and compatibility with roleto-role processing for low-cost, large-area fabrication. Numerous ordered mesoporous carbons from block copolymer (BCP) soft-templating have been reported with pore sizes of below 15 nm for Pluronics templates and up to 40 nm with high molar mass BCPs. Surface areas range from 150 to 1000 m 2 g −1 , dependent on pore size, carbonization temperature, and microporosity. 14−19 Only a few hierarchical macro-and mesoporous carbons have been reported using one-pot hydrothermal synthesis or spinodal decomposition. 20,21 Recently, BCPs have been used for the fabrication of graded, hierarchically macro-and mesoporous polymer membranes with ordered features on th...

Polymer‐Based Synthetic Routes to Carbon‐Based Metal‐Free Catalysts

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Anisotropic Magnetism in Gradient Porous Carbon Composite Aerogels

“…However, studies regarding porous FGMs are mostly of a theoretical nature, mainly due to the lack of established synthesis procedures [26]. The employed synthesis methods include, among others, anisotropic microphase separation [27], foam templating [28] and sintering-dissolution processes [29]. Among these methods, only a few allow for a precise control over the final pore sizes.…”

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Laser-induced hierarchically-structured materials from block copolymer self-assembly

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