Mesopore size control

The pore size of mesoporous carbon is of importance with respect to practical applications. When mesoporous carbon is synthesised via soft-template methods, the self-assembly of organic-organic species and pore size can be influenced by synthesis conditions, including surfactant type and concentration, and synthesis temperature. For example, Meng et al. observed that the pore size of mesoporous carbon derived from soft-templated mesoporous polymer composites decreased from 7.4 to 5.9 nm when the pyrolysis temperature increased from 400 to 800 How- 

---

Ma, X. M., L. H. Gan, M. X. Liu et al. 2014. Mesoporous size controllable carbon microspheres and their electrochemical performances for supercapacitor electrodes. Journal of Materials Chemistry A 2 8407-8415. 

Scheme 1. Inclusion of size-controlled PVP-protected Pt nanoparticles in calcined mesoporous SBA-15 silica matrices. Mechanical agitation by low-power sonication affords a high dispersion of nanoparticles ranging in size from 1 to 7nm in the mesopore channels. The method is referred to as capillary inclusion (Cl). The technique is limited by the size of nanoparticles that can fit into the 6-9 nm diameter mesopores [13]. (Reprinted from Ref [13], 2005, with permission from American Chemical Society.)...

By using other templates, the size of metal nanoparticles can be also controlled. Chen et al. reported the sonochemical reduction of Au(III), Ag(I) and Pd(II) and synthesis of Au, Ag and Pd nanoparticles loaded within mesoporous silica [48,49]. Zhu et al. also reported the sonochemical reduction of Mn04 to Mn02 and synthesis of Mn02 nanoparticles inside the pore channels of ordered mesoporous cabon [50]. Taking into account these reports, the rigid pore of inorganic materials can be used as a template for the size controlled metal nanoparticle synthesis even in the presence of ultrasound. 

One of the most promising applications of enzyme-immobilized mesoporous materials is as microscopic reactors. Galameau et al. investigated the effect of mesoporous silica structures and their surface natures on the activity of immobilized lipases [199]. Too hydrophilic (pure silica) or too hydrophobic (butyl-grafted silica) supports are not appropriate for the development of high activity for lipases. An adequate hydrophobic/hydrophilic balance of the support, such as a supported-micelle, provides the best route to enhance lipase activity. They also encapsulated the lipases in sponge mesoporous silicates, a new procedure based on the addition of a mixture of lecithin and amines to a sol-gel synthesis to provide pore-size control. 

Khodakov, A.Y., Griboval-Constant, A., Bechara, R., and Villain, F. 2001. Pore-size control of cobalt dispersion and reducibility in mesoporous silicas. J. Phys. Chem. B 105 9805-11. 

The effect of the modifiers appears to be more evident in the case of Ru-MCM-41 catalysts. The size-controlled mesoporous channels of MCM-41 affords a better interaction of the prostaglandin intermediates with modifiers [274,275],... 

Jhung, S.H., Lee, J.H., and Chang, J. (2008) Crystal size control of transition metal ion-incorporated aluminophos-phate molecular sieves effect of ramping rate in the syntheses. Micropor. Mesopor. Mater., 112, 178-185. 

Mesoporous silicas are characterized by surface areas 10 to 20 times larger than that of zeolites, typically around 1000 cm2 g. The pores can be adjusted in a range between 2 and 30 nm, and the pore volumes range between 0.5 and 2.5 cm3 g . The mesopore sizes and volumes are ideal for chemical reactions to take place in their interior, therefore the ability to block the pore entrances with stimuli responsive gates enables a control in chemical reactivity suitable for a variety of applications, including selective sensing, catalysis, and delivery, among others. 

Little information is however available about the effect of catalyst mesoporosity on FT catalytic behavior. Broad distribution of mesopore sizes in amorphous oxides makes it difficult to quantify this effect. On the contrary, SBA-15 and MCM-41 periodic mesoporous silicas [7-8] with uniform pore size distributions could provide new insights into the effects of catalyst pores on the structure and catalytic behavior of FT catalysts. This paper focuses on the effects of support mesoporosity on the structure and catalytic behavior of cobalt supported FT catalysts. In addition, we aim to demonstrate that the support mesoporosity could provide an efficient tool for the control of catalytic performance of supported FT catalysts. 

K [1,3], which would result in the drastic increase of the mesopore in the activated carbons synthesized in 100% Hj. Based on these mechanisms of the mesopore production, control of the particle size of the Fe compound should be important to produce mesopores. The size of the particles can be controllable through adjustment of the introduced amount of Fe in the precursor, dispersion of Fe at the preparation stage of the precursor and the condition of heat-treatment such as heating rate and treatment temperature. The conditions should be optimized depending on precursors. We also confirmed the effectiveness of the present method in selective increase of mesopores of activated carbons using used coffee beans and tea leaves wastes. The results will be presented in the next paper. 

C. Shao, X. Li, S. Qiu, F. Xiao, and O.Terasaki, Size-controlled Synthesis of Silicalite-1 Single Crystals in the Presence of Benzene-1,2-diol. Microporous Mesoporous Mater., 2000,... 

Although studies on the subject of ordered mesoporous materials were started about 15 years ago, the unique structure and the properties of these materials attracted many scientists in different fields of research. Their efforts resulted in fruitful results that have been reported in thousands of publications. The flexibility and complexity of their synthesis and structure, and the extensive application potentials of mesoporous materials, create a huge opportunity for researchers and developmental scientists. This chapter will summarize the research results on mesoporous materials from syntheses, structures, formation mechanisms, compositions, morphologies, pore-size control, modifications, applications, challenges, and so on. 

The biggest advantage of ordered mesoporous materials is their uniform mesopores pore control is very important for theses mesoporous materials. The mesopore system (pore shape and array of pores) can be controlled by varying different mesostructures. In this section, the general methods to control pore size will be discussed. 

Ordered mesoporous materials, due to their periodic and size-controllable pore channels and high surface areas, have been regarded as a nano-reactor to construct novel ordered and well dispersed nanostructured composites with controlled size and size distribution.[303] A number of studies have reported on the encapsulation of guest materials, such as metal oxides,[304] semiconductors, metal sulfides,[305] carbon, metals,[306] and polymers into mesoporous silica hosts. 

Lee. K.B. Lee. S.M. Cheon, J. Size-controlled synthesis of Pd nanowires using a mesoporous silica template via chemical vapor infiltration. Adv. Mater. 2001, 13, 517. 

---