Surface functionalization of ordered mesoporous carbons--a comparative study

Hexagonally structured mesoporous carbons C15 and CMK-5 and cubically structured carbon C48 were synthesized using ordered silica SBA-15 and MCM-48 as templates and carbon precursors of different structures. The surfaces of these ordered carbons were chemically functionalized by employing an approach, in which the selected diazonium compounds were in situ generated and reacted with the carbon frameworks of the mesoporous carbons. The aromatic organic molecules containing chlorine, ester, and alkyl groups were covalently attached to the surface of these ordered mesoporous carbons. The presence of functional groups on the modified carbons was confirmed with Fourier transform infrared spectroscopy, thermogravimetric analysis, and nitrogen adsorption. The BET-specific surface area and the pore width of ordered carbons were significantly reduced, whereas the primary structure of these ordered carbons and their unit cells were intact. Basically, the density of grafted functional groups is related to the specific surface area of the sample, particularly the surface area of mesopores. The surface functionalization reaction takes place only on the external surface of carbon C15, while it occurs on both of the internal and external surface of CMK-5 carbon with the nanopipe structure. The presence of the micropores in CMK-5 carbon should be responsible for its lower grafting density because the small micropores are inaccessible in the reaction. It was also proposed that the preferred adsorption/reaction in C48 may be related to the observed unsymmetrical degradation of the XRD patterns for the functionalized C48 samples. The chemical modification process considerably reduced the primary mesopores in these ordered carbons by approximately 1-1.5 nm, affording carbons with micropores in the cases of C15 and C48, and mixed micropores and small mesopores in the case of CMK-5. A grafting density of approximately 0.9-1.5 micromol/m(2) was achieved under current research.     

Partially graphitized ordered mesoporous carbons for high-rate supercapacitors

Partially graphitized ordered mesoporous carbons have been prepared with a soft template method using low-molecular-weight phenolic resol as a carbon source, triblock copolymer F127 as a template, and ferric citrate as a graphitization catalyst. N₂ sorption and transmission electron microscopy analysis show that the ordered mesoporous carbons have been partially graphitized when the carbonization temperature is above 700 °C. The graphitic ordered mesoporous carbons exhibit better rate performance than amorphous ordered mesoporous carbons. The specific capacitance of the graphitic ordered mesoporous carbons (GOMCs) prepared at 700 °C reaches to 112 F g^?1 at a scan rate of up to 1,000 mV s^?1. Its capacitance retention ratio is 64 %, which is much higher than that of the amorphous ordered mesoporous carbons prepared at 600 °C (33 %). High electronic conductivity and ordered mesoporous structure lead to the high electrochemical performance of the partially graphitized ordered mesoporous carbons.     

Ordered porous carbon with tailored pore size for electrochemical hydrogen storage application

Ordered porous carbon with tailored pore size represents an innovative concept in electrochemical hydrogen storage. This work deals with physical characteristics and electrochemical hydrogen storage behavior of the ordered porous carbons with well-tailored pore size, synthesized by a replica technique using hexagonal mesoporous silica as templates. By using a mixture of two surfactants (HTAB and C16EO8) at different ratios, it is possible to control the wall thickness of silica and, consequently, the pore diameter of carbons within a narrow range of 2.1-2.8 nm. In addition, highly developed ultramicroporosity (pore size smaller than 0.7 nm), which plays a predominant role in hydrogen storage, can be produced in the ordered porous carbons. A discharge capacity of up to 527 mAh/g (corresponding to 1.95 wt % hydrogen storage) has been achieved in 6 M KOH for the ordered porous carbon. Furthermore, the ordered porous carbons also possess excellent capacity retainability after charge-discharge cycles and rate capability.     

Three-dimensionally ordered macroporous carbons having walls composed of hollow mesosized spheres

Three-dimensionally ordered macroporous carbons were prepared from bimodal polymer-silica colloidal crystals; the resulting carbons had interconnected macropores, and the walls of the macropores were composed of hollow mesosized spheres.     

Ordered mesoporous carbon catalyst for dehydrogenation of propane to propylene

Metal-free ordered mesoporous carbons were demonstrated to be robust catalysts for direct dehydrogenation of propane to propylene, in the absence of any auxiliary steam, exhibiting high activity and selectivity, as well as long catalytic stability, in comparison with nanostructured carbons.     

Organic acid-assisted soft-templating synthesis of ordered mesoporous carbons

A series of soft-templated ordered mesoporous carbons (OMCs) was synthesized by using resorcinol and formaldehyde as carbon precursors, triblock copolymer Pluronic F127 as a soft-template, and an organic acid (acetic, benzoic, citric, oxalic, or succinic) as a polymerization reaction catalyst. The aforementioned organic acids were strong enough to facilitate the formation of ordered mesophases by the block copolymer template used and to catalyze the polymerization reaction of resorcinol and formaldehyde in this template. The use of weak organic acids instead of strong inorganic acids such as HCl eliminated inorganic anions from the reaction environment and resulted in high surface area OMCs. Basically, the resulting carbons showed the surface areas and pore volumes comparable to those reported for the carbons prepared under similar conditions but in the presence of strong inorganic acids. Electron microscopy analysis proved the presence of ordered mesopores, whereas thermogravimetric analysis showed a good thermal stability of these carbons.     

有序介孔炭的合成及液相有机大分子吸附性能研究

分别采用有序介孔氧化硅SBA-15和NaY分子筛为硬模板合成了系列有序介孔炭OMC和微孔炭CFY. N₂静态吸附测试表明, 所合成的介孔炭具有丰富的介孔结构和集中的介孔分布. 以亚甲基蓝为探针分子, 研究其在有序介孔炭OMC和微孔炭CFY上的吸附行为. 研究结果表明, 有序介孔炭中大于3.5 nm的大介孔孔容是决定亚甲基蓝吸附容量和吸附速率的关键因素. 吸附动力学理论研究表明, 准二级动力学方程可以很好地描述亚甲基蓝分子在介孔炭上吸附动力学行为.     

Synthesis of Ordered Mesoporous Carbon Materials by Dry Etching

A novel synthesis method for ordered mesoporous carbons is presented. The inverse replication of a silica template was achieved using the carbonization of sucrose within mesoporous KIT‐6. Instead of liquid acid etching, as in classical nanocasting, a novel dry chlorine etching procedure for template removal is presented for the first time. The resultant ordered mesostructured carbon material outperforms carbons obtained by conventional hard templating with respect to high specific micro‐ and mesopore volumes (0.6 and 1.6 cm³ g^?1, respectively), due to the presence of a hierarchical pore system. A high specific surface area of 1671 m² g^?1 was achieved, rendering this synthesis route a highly convenient method to produce ordered mesoporous carbons.     

Synthesis of mesoporous carbons using ordered and disordered mesoporous silica templates and polyacrylonitrile as carbon precursor

Mesoporous carbons were synthesized from polyacrylonitrile (PAN) using ordered and disordered mesoporous silica templates and were characterized using transmission electron microscopy (TEM), powder X-ray diffraction, nitrogen adsorption, and thermogravimetry. The pores of the silica templates were infiltrated with carbon precursor (PAN) via polymerization of acrylonitrile from initiation sites chemically bonded to the silica surface. This polymerization method is expected to allow for a uniform filling of the template with PAN and to minimize the introduction of nontemplated PAN, thus mitigating the formation of nontemplated carbon. PAN was stabilized by heating to 573 K under air and carbonized under N2 at 1073 K. The resulting carbons exhibited high total pore volumes (1.5-1.8 cm3 g(-1)), with a primary contribution of the mesopore volume and with relatively low microporosity. The carbons synthesized using mesoporous templates with a 2-dimensional hexagonal structure (SBA-15 silica) and a face-centered cubic structure (FDU-1 silica) exhibited narrow pore size distributions (PSDs), whereas the carbon synthesized using disordered silica gel template had broader PSD. TEM showed that the SBA-15-templated carbon was composed of arrays of long, straight, or curved nanorods aligned in 2-D hexagonal arrays. The carbon replica of FDU-1 silica appeared to be composed of ordered arrays of spheres. XRD provided evidence of some degree of ordering of graphene sheets in the carbon frameworks. Elemental analysis showed that the carbons contain an appreciable amount of nitrogen. The use of our novel infiltration method and PAN as a carbon precursor allowed us to obtain ordered mesoporous carbons (OMCs) with (i) very high mesopore volume, (ii) low microporosity, (iii) low secondary mesoporosity, (iv) large pore diameter (8-12 nm), and (v) semi-graphitic framework, which represent a desirable combination of features that has not been realized before for OMCs.     

Synthesis of ordered mesoporous carbons with channel structure from an organic-organic nanocomposite

Mesoporous carbons with ordered channel structure (COU-1) have been successfully fabricated via a direct carbonization of an organic-organic nanocomposite.     

A facile aqueous route to synthesize highly ordered mesoporous polymers and carbon frameworks with Ia3d bicontinuous cubic structure

By employing an organic-organic self-assembly in a dilute aqueous solution, novel ordered bicontinuous cubic mesoporous polymers and carbons with Iad symmetry are directly synthesized.     

Influence of the Morphology of Mesoporous Carbon on the Electrocatalytic Activity of Pt in Oxygen Reduction

Russian Journal of Applied Chemistry - Mesostructured silicates MCM-48, SBA-15, and MCM-41 were synthesized, and the corresponding ordered mesoporous carbons CMK-1, CMK-3, and CS41 were prepared on...     

One-pot synthesized MoC imbedded in ordered mesoporous carbon as a catalyst for N2H4 decomposition

Nanosized and highly dispersed molybdenum carbide was fabricated in the carbon walls, along with the formation of ordered mesoporous carbons, via a one-pot organic-organic cooperative self-assembly approach.     

Characterization of the pore structure of three-dimensionally ordered mesoporous carbons using high resolution gas sorption

The use of colloidal crystals with various primary particle sizes as templates leads to the formation of three-dimensionally ordered mesoporous (3DOm) carbons containing spherical pores with tailorable pore size and extremely high pore volumes. We present a comprehensive structural characterization of these novel carbons by using nitrogen (77.4 K) and argon (87.3 K) adsorption coupled with the application of novel, dedicated quenched solid density functional theory (QSDFT) methods which assume correctly the underlying spherical pore geometry and also the underlying adsorption mechanism. The observed adsorption isotherms are of Type IV with Type H1-like hysteresis, despite the fact that pore blocking affects the position of the desorption branch. This follows also from detailed, advanced scanning hysteresis experiments which not only allow one to identify the underlying mechanisms of hysteresis, but also provide complementary information about the texture of these unique porous materials. This work addresses the problem of pore size analysis of novel, ordered porous carbons and highlights the importance of hysteresis scanning experiments for textural analysis of the pore network.     

有序中孔炭的电化学储氢性能

将蔗糖、聚环氧乙烯-聚环氧丙烯-聚环氧乙烯三嵌段共聚物和硅源构成的复合物进行预炭化、炭化和除硅处理合成出有序中孔炭, 采用XRD、TEM、HRTEM和N2吸脱附等手段对其进行表征, 并将有序中孔炭制成电极开展恒流充放电储氢性能研究. 结果显示, 具有较高比表面积(720 m2·g-1)和孔容(0.86 cm3·g-1)的有序中孔炭材料的电化学储氢容量为70.1 mAh·g-1, 高于具有相对较低比表面积(610 m2·g-1)和孔容(0.66 cm3·g-1)的有序中孔炭储氢容量(64.1 mAh·g-1). 通过与单壁碳纳米管电极(25.9 mAh·g-1)的对比, 表明有序中孔炭具有良好的电化学储氢性能和更高的电化学活性.     

A direct template synthesis of nanoporous carbons with high mechanical stability using as-synthesized MCM-48 hosts

A simple and efficient synthetic method for highly ordered nanoporous carbons with high mechanical and thermal stability has been performed through a direct template carbonization using as-synthesized MCM-48 hosts.     

Rational design of ordered mesoporous carbon with controlled bimodal porosity via dual silica templating route

Combining both nano-replication and nano-imprinting techniques using dual silica templates provides a simple way to synthesize ordered mesoporous carbons with bimodal pore size distributions ( approximately 1.5 nm and approximately 3.5 nm).     

Novel pitch-based carbons with bimodal distribution of uniform mesopores

A new method is proposed for the synthesis of pitch-based carbons with bimodal distribution of uniform mesopores formed by co-imprinting of spherical silica colloids and hexagonally ordered mesoporous particles of SBA-15 into mesophase pitch particles and subsequent silica dissolution.     

Aminated Ordered Mesoporous Carbons: Preparation and Catalytic Performance for Knoevenagel Condensation Reactions

The amine‐ and diamine‐functionalized mesoporous carbons with hexagonal mesostructure have been prepared by a rationally two‐step modification procedure under mild reaction conditions, respectively. The physicochemical properties of the obtained solid basic mesoporous catalysts were characterized by XRD, TEM, N₂ adsorption‐desorption, FT‐IR, EDX and elemental analysis techniques. The results indicated the organic amine groups were successfully introduced inside the channels of mesoporous carbons without destroying the well‐ordered 2D hexagonal mesostructure. A series of Knoevenagel condensation of aldehyde/ketone with active methylene compounds have been carried out over the diamine‐function‐ alized mesoporous carbons, which proved to be efficient heterogeneous basic catalysts and exhibited a similar catalytic activity after sixth cycles. This can be attributed to its hydrophobic framework and hydrophilic diamine groups, which led to amphiphilic properties and offered some advantages for the Knoevenagel condensation reactions.     

Triconstituent co-assembly to ordered mesostructured polymer-silica and carbon-silica nanocomposites and large-pore mesoporous carbons with high surface areas

Highly ordered mesoporous polymer-silica and carbon-silica nanocomposites with interpenetrating networks have been successfully synthesized by the evaporation-induced triconstituent co-assembly method, wherein soluble resol polymer is used as an organic precursor, prehydrolyzed TEOS is used as an inorganic precursor, and triblock copolymer F127 is used as a template. It is proposed for the first time that ordered mesoporous nanocomposites have "reinforced concrete"-structured frameworks. By adjusting the initial mass ratios of TEOS to resol, we determined the obtained nanocomposites possess continuous composition with the ratios ranging from zero to infinity for the two constituents that are "homogeneously" dispersed inside the pore walls. The presence of silicates in nanocomposites dramatically inhibits framework shrinkage during the calcination, resulting in highly ordered large-pore mesoporous carbon-silica nanocomposites. Combustion in air or etching in HF solution can remove carbon or silica from the carbon-silica nanocomposites and yield ordered mesoporous pure silica or carbon frameworks. The process generates plenty of small pores in carbon or/and silica pore walls. Ordered mesoporous carbons can then be obtained with large pore sizes of approximately 6.7 nm, pore volumes of approximately 2.0 cm(3)/g, and high surface areas of approximately 2470 m(2)/g. The pore structures and textures can be controlled by varying the sizes and polymerization degrees of two constituent precursors. Accordingly, by simply tuning the aging time of TEOS, ordered mesoporous carbons with evident bimodal pores at 2.6 and 5.8 nm can be synthesized.