14 Common Types Of Porous Materials

UPAC separates pores into micropores (<2 nm), mesopores or mesopores (2 to 50 nm), macropores (> 50 nm) according to the pore size scale; according to the latest definition, the pores are subdivided into Micropores (<0.7 nm) and micropoles (0.7-2 nm), while wells below 100 nm are collectively referred to as nanopores. So how are the names of these hole materials come from?

MCM series

MCM is short for Mobil Composition of Matter. Mainly by the Mobil Oil researchers, using ethyl silicate as a silicon source, synthesized by a micelle-based soft template method. MCM The Musketeers are MCM-41, MCM-48 and MCM-50. MCM-41 is a hexagonal mesoporous structure, the arrangement of a regular cylindrical mesopores made of one-dimensional pore structure. Mesopore diameter adjustable between 2-6.5 nm, large specific surface area. Compared to molecular sieves, there is no Bronsted acid sites in MCM-41. Due to its thin wall and low exchange rate of silicon units, Si-O bonds hydrolyze and re-crosslink in boiling water, resulting in structural damage. Therefore, Thermal stability is not good. The earliest papers on the synthesis of MCM-41 were published in the JACs in 1992, and the citations now have nearly 12,000 citations. (J. Am. Chem. Soc., 1992, 114 (27), pp 10834-10843.) MCM-48 has a three-dimensionally interconnected cell structure. MCM-50 is a lamellar structure and can only be referred to as “mesostructure” rather than “mesoporous” since the lamellar structure collapses upon removal of the surfactant-forming layer, and since there is no pore, this is not Deep down. 

Figure 1 MCM-41 synthesis mechanism diagram, the surfactant used is an anionic surfactant

SBA series

SBA is short for Santa Barbara Amorphous. Among them, the big name is SBA-15. SBA-15 was first synthesized by Zhao Dongyuan, a teacher at Fudan University in 1998 after doing a post-graduate study at Santa Barbara, University of California, U.S.A. It was published in Science that year and has been quoted for more than 10,000 times (Science 23 Jan 1998: 279, 5350, 548-552.). SBA series of mesoporous silica materials are synthesized using a soft template method using a block type surfactant; its pore size is adjustable in the range of 5-30 nm. SBA-15 consists of a series of hexagonal parallel cylindrical channels with a few mesopores or pores arranged in random order with a cell wall thickness of 3-6 nm. Due to the thicker cell walls of SBA-15, the hydrothermal stability of the material is better than that of the MCM series. SBA-15 is a multi-dimensional porous material that contains both mesoporous materials. It can remove the surfactant embedded in the pore walls during the calcination process, resulting in a microporous structure.

Figure 2 (left) TEM image of SBA-15 with different pore sizes. The hydrophobic end of the (right) triblock surfactant will enter the pore walls of the formed silica. After calcination, the micropores

HMM series

HMM is an abbreviation of Hiroshima Mesoporous Material and was first prepared by researchers from Hiroshima University in 2009. HMM is a spherical mesoporous silicon material with a pore size of 4-15 nm and an adjustable outer diameter of 20-80 nm. In the synthesis step, the authors first form emulsion droplets through the oil / water / surfactant mixed solution and then grow the silicon with the in situ generated polystyrene particles as a template, resulting in spherical mesoporous silica after the template is removed. (Microporous and Mesoporous Materials 120 (2009) 447-453.)

Figure 3 HMM synthesis mechanism diagram and product SEM and TEM images

TUD series

TUD stands for Technische Universiteit Delft, also known as Delft University of Technology. In the electron micrograph TUD-1 appears as a foam with a surface area of ​​400-1000 m2 / g and a tunable mesopore between 2.5 and 25 nm. In the synthesis of materials, there is no surfactant, and triethylamine is used as organic template agent. The pore structure can be controlled by adjusting the ratio of organic template agent and silicon source. (Chem. Commun., 2001, 713-714)

Figure 4 (left) SEM image of TDU-1, (right) Mesoporous carbon material synthesized with TDU-1 as a hard template

FSM series

FSM is short for Folded Sheets Mesoporous Materials. Literal translation of its name is, folded sheet mesoporous material. FSM synthesis is the synthesis of layered silicate material Kanemite and long-chain alkyl trimethylamine (ATMA) under alkaline conditions mixed treatment ion exchange occurs to obtain a narrow pore size distribution of three-dimensional hexagonal mesoporous silica material. FSC has a specific surface area of ​​650-1000 m2 / g and a pore size of 1.5-3 nm. (Bull. Chem. Soc. Jpn., 69, No. 5 (1996))

Figure 5 TEM diagram of the FSM

KIT series

KIT did not find a very official statement, most likely the abbreviation of Korea Advanced Institute of Science and Technology. Also belonging to the ordered mesoporous silica material, different from the SBA-15 (cubic p6mm) unidirectional pore structure, KIT-6 (cubic la3d) has interconnected cubic mesoporous structure. In the synthesis of KIT-6, a mixture of triblock surfactant (EO20PO70EO20) and butanol was used as a structure-directing agent. KIT-6 pore size adjustable in 4-12 nm, the specific surface area of ​​960-2200 m2 g-1. (Chem. Commun., 2003, 2136-2137)

Figure 6 (left) Structure diagram of SBA-15 p6mm and KIT-6 la3d, (right) TEM image of KIT-6

CMK series

The common method for synthesizing mesoporous carbon is the hard template method. Mesoporous molecular sieves such as MCM-48 and SBA-15 are used as template to select the appropriate precursors, carbonize the precursors under the catalysis of acid and deposit on the pores of mesoporous materials Road, and then dissolved with NaOH or HF mesoporous SiO2, to get mesoporous carbon. In 1999, Ryoo succeeded in replicating other mesoporous materials using mesoporous materials as hard templates. This series of materials named CMK. Also did not find the official naming, but most likely Carbon Molecular Sieves and Korea combined naming. He has successively produced CMK-1, CMK-2, CMK-3, CMK-8 and CMK-9 mesoporous carbon molecular sieve materials using MCM-48, SBA-1, SBA-15 and KIT-6 as templates. (J. Phys. Chem. B, 103, 37, 1999.) CMK-3 is a two-dimensional hexagonal structure with a narrow pore size distribution, high specific surface area (1000-2000 m2 / g), large pore volume 1.35 cm3 / g) and strong acid and alkali resistance, is a good catalyst carrier.

Figure 7 TEM image of CMK-1 and CMK-3

FDU series

FDU series is short for Fudan University and is the work done by Zhao Dongyuan teacher after returning to Fudan University. FDU is a series of phenolic resins synthesized by soft-template method. The ordered mesoporous carbon materials can be synthesized by high-temperature carbonization and consist of spherical pores. The same is the use of surfactant as a structure-directing agent, the use of phenolic resin precursors as raw materials, by solvent evaporation self-assembly method to get the orderly structure. (Angew. Chem. Int. Ed. 2005, 44, 7053-7045)

Figure 8 FDU-15 and FDU-16 after high-temperature carbonizationStarbon

STARBON Series

Starbon is the name of the mesoporous carbon material. Because the original Starbon was synthesized by researchers at the University of York by the sol-gel method of Starch and then carbonized. Therefore, its name is Starbon, and registered the brand name “Starbon”. Starbon mesopore volume of 2.0 cm3 / g, the specific surface area of ​​500 m2 / g, can be used as a catalyst carrier, gas adsorption or water purification agent. Now Starbon raw materials can be extended to pectin and alginic acid.

Figure 9 (left) Starbon synthesis step, (right) SEM image of Starbon

ZSM series

ZSM is an abbreviation for Zeolite Socony Mobil, and ZSM-5 is a trade name, which is the fifth Zeolite found by Socony Mobil Corporation. Synthetized in 1975, Nature reported its structure in 1978. ZSM-5 is an orthorhombic system. It is a kind of zeolite molecular sieve with three-dimensional cross-channels with high silicon and five-membered rings. It is oleophilic and hydrophobic, has high thermal and hydrothermal stability, and most of the pores have a diameter of about 0.55 nm Hole Zeolite.

Figure 10 TPABr synthesized ZSM-5

AlPO series

AlPO is the abbreviation of acid-free microporous aluminophosphate molecular sieve, which is the “second-generation molecular sieve” developed by the UOP Company of the United States since the 1980s. These molecular sieve frameworks are composed of an equal amount of AlO4- and PO4- tetrahedra and are electrically neutral and show weaker acid-catalyzing properties. With the introduction of heteroatoms, the original charge balance of the AlPO zeolite framework can be broken down , So that its acidity, adsorption performance and catalytic activity were significantly improved. The framework structure of AlPO4-5 belongs to the hexagonal system, with a typical 12-membered ring main channel with a pore size of 0.76 nm, which is comparable to that of aromatics.

SAPO series

SAPO is the abbreviation from Silicoaluminophosphate, SAPO-34 is the molecular sieve first reported by UCC in 1982, and 34 is the code. The skeleton of SAPO-34 is composed of PO2 +, SiO2, AlO2- and has three-dimensional cross-channels, eight-ring pore diameter and moderate acid sites. As well as adsorption separation and membrane separation showed excellent performance. The composition of SAPO-11 is Si, P, Al and O four kinds, its composition can be changed in a wide range, the silicon content of the product varies with the synthesis conditions. SAPO-11 mesoporous zeolite, with one-dimensional ten-ring structure, into an oval hole. The SAPO molecular sieve framework is negatively charged and therefore has exchangeable cations and has protonic acidity. SAPO molecular sieve can be used as adsorbent, catalyst and catalyst carrier.

Figure 11 SEM image of SAPO-11 with a crystallization time of 48h


There are several other Porous Materials that are not commonly used:
MSU  (Michigan State University) is a series of mesoporous molecular sieves developed by Pinnavaia et al. Of the University of Michigan. MSU-X (MSU-1, MSU-2 and MSU-3) . MSU-V, MSU-G have a layered structure of multilamellar vesicles.

HMS

(Hexagonal Mesoporous Silica) is a mesoporous molecular sieve developed by Pinnavaia et al., Which is also a hexagonal structure with a low degree of order.

APMs

(acid-prepared mesostructures), an early research by Stucky et al., Were prepared under acidic conditions and were an extension of the MCM series of synthetic processes (alkaline media).
Not only the name is very unique, the application of porous materials is also very extensive, are:

1. Efficient gas separation membrane;

2. Chemical process catalytic membrane;

3.Substrate materials for high-speed electronic systems;

4. precursors for optical communication materials;

5. highly efficient thermal insulation materials;

6. porous electrodes for fuel cells;

7. separation media and electrodes for batteries;

8. fuels (including natural gas and hydrogen) Of the storage medium;

9. Selection of environmentally clean up absorbent;

10. Special reusable filter. These applications will have a profound impact on industrial applications and people’s daily lives.


References:1. J. Am. Chem. Soc., 1992, 114 (27), pp 10834-10843.2. Science 23 Jan 1998: 279, 5350, 548-552.3. Microporous and Mesoporous Materials 120 (2009) 447-453.4. Chem. Commun., 2001, 713-714.5. Bull. Chem. Soc. Jpn., 69, No. 5 (1996)6. J. Chem. Soc., Chem. Commun. 1993, 8, 680.7. Chem. Commun., 2003, 2136-2137.8. J. Phys. Chem. B, 103, 37, 1999.9. Angew. Chem. Int. Ed. 2005, 44, 7053-7059.

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