Structure of Porous Aggregates of the Ammonium Salt of Dodecatungstophosphoric Acid, (NH4)3PW12O40:  Unidirectionally Oriented Self-Assembly of Nanocrystallites

Ito, Takeru; Inumaru, Kei; Misono, Makoto

doi:10.1021/jp9714835

Cited by 77 publications

(63 citation statements)

References 26 publications

(48 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The XRD patterns of (NH 4 ) 3 PW 12 O 40 /SiO 2 having W/Si molar ratio of 2/8 revealed that the Keggin structure of (NH 4 ) 3 PW 12 O 40 was maintained which was calcined at 450°C or less. The XRD pattern of (NH 4 ) 3-PW 12 O 40 /SiO 2 is consistent to that of (NH 4 ) 3 PW 12 O 40 in the reported papers [22,23]. Izumi et al have reported that (NH 4 ) 3 PW 12 O 40 was converted to (NH 4 ) 2-HPW 12 O 40 when it was heated at 450°C for 2 h, which was determined by thermogravimetric analysis [24].…”

Section: Resultssupporting

confidence: 81%

Polymer synthesis by solid-acid catalyst based on heteropolyacid ammonium salt

et al. 2015

View full text Add to dashboard Cite

Ring-opening polymerizations of four kinds of monomers such as glycidyl phenyl ether, oxetane (OX), e-caprolactone (CL), and 2,2-dimethyltrimethylene carbonate were performed with a silica-supported catalyst based on heteropolyacid ammonium salt, (NH 4 ) 3 PW 12 O 40 /SiO 2 . Preparation of the catalyst was done by an impregnation of (NH 4 ) 3 PW 12 O 40 onto SiO 2 in aqueous ammonia, followed by its calcination. Selectivities for skeletal isomerizations of 1-butene exhibited a strong acidity of the (NH 4 ) 3 PW 12 O 40 /SiO 2 . Among four monomers, the OX and CL were the promising monomers for this polymerization system. The resulting poly(OX) and poly(CL) with number-average molecular weight (M n ) of 2900-6500 and 5500-8600 were obtained in 65-80 and 93-96 % yields, respectively. Furthermore, copolymerization of OX and CL successfully proceeded, affording poly(OX-co-CL) with compositions of OX:CL = 63:37, 50:50, and 37:63 having M n = 2400-3800 in 64-84 % yields.

show abstract

Section: Resultssupporting

confidence: 81%

Polymer synthesis by solid-acid catalyst based on heteropolyacid ammonium salt

et al. 2015

View full text Add to dashboard Cite

show abstract

“…[76][77][78] Self-organization seems to allow control even at the supramolecular scale. [46,79,80] In situ studies cast considerable doubt, however, on the allegation that these solids are active in their as-prepared form; their surfacse seem to exhibit differences from the crystalline bulk, and hence a detailed understanding of their structural dynamics is required to control the genesis and stability of the active sites. [81,82] Another strategy is to reduce the size of the active site to a very small number of atoms to prepare "single-site" catalysts, which offer the chance to exactly control the active site and its environment on the molecular scale.…”

Section: Alternative Routes To Controlled Synthesismentioning

confidence: 99%

Nanocatalysis: Mature Science Revisited or Something Really New?

2004

View full text Add to dashboard Cite

"Nanomania" has reached the area of heterogeneous catalysis. Nanosized catalyst constituents are important for functions that require structural control over several scales of dimension. Nanocatalysis may be understood as a redefinition of catalyst synthesis: multidimensional structural control is exerted by considering catalysts as inorganic polymers rather than as close-packed crystals. Primary, secondary, and tertiary structural hierarchies translate into molecular building blocks and linkers, the defect structure of crystals, and particle morphology. High-throughput techniques and in situ synthetic analysis are the tools required to arrive at better defined catalytic materials that can fulfil the high expectations created by the incorporation of catalysts into the "nano" research field.

show abstract

“…Moreover, necks between the crystallites were found to grow epitaxially during the formation process, enabling the nanocrystallites to form strong connection with each other; a phenomenon we defined as ''Epitaxial Self Assembly'' [17][18][19][20][21][22][23], as shown in figure 1. In this non-classical crystallization mechanism, the nanocrystallites form in supersaturated solutions, aggregating in an ordered manner, gaining higher crystallinity in the process.…”

Section: Introductionmentioning

confidence: 99%

“Sponge Crystal”: a novel class of microporous single crystals formed by self-assembly of polyoxometalate (NH4)3PW12O40 nanocrystallites

Inumaru

2006

Catal Surv Asia

Self Cite

View full text Add to dashboard Cite

In this account, a new concept of ''sponge crystals'' is presented on the basis of new interpretation of our previous results of porous heteropolyacids, that is, porous aggregates of self-assembled (NH 4 ) 3 PW 12 O 40 nanocrystallites (Ito, Inumaru, and Misono, J. Phys. Chem. B 101 (1997) 9958; Chem. Mater. 13 (2001) 824) ''Sponge crystals'' are defined as single crystals having continuous voids within them, but unlike zeolites, no intrinsic structural pores. This new category includes molecular single crystals having continuous voids originating from series of neighboring vacancies ( ‡1 nm) of the constituent large molecules, affording nanospaces in the crystals. A typical example of ''sponge crystals'' is (NH 4 ) 3 PW 12 O 40 , which is formed via the dropwise addition of ammonium hydrogen carbonate into an H 3 PW 12 O 40 aqueous solution (titration method) at 368 K. The resulting (NH 4 ) 3 PW 12 O 40 nanocrystallites (ca. 6-8 nm) then self-assemble with the same crystal orientation to form porous dodecahedral aggregates in the solution. During the formation process, necks grow epitaxially between the surfaces of the nanocrystallites (''Epitaxial SelfAssembly'') to form aggregates of which each aggregate has an ordered structure as a whole single crystal. Although the crystal structure of (NH 4 ) 3 PW 12 O 40 has no intrinsic structural(''built-in'') pores, X-ray diffraction, electron diffraction and gas adsorption experiments all reveal that each (NH 4 ) 3 PW 12 O 40 aggregate is comprised of a single crystal bearing many micropores. These pores are considered to be continuous spaces as neighboring vacancies of the molecules (anions and cations) originating from the residual spaces between the self-assembled nanocrystallites. The porous (NH 4 ) 3 PW 12 O 40 single crystals are considered a special case of ''mesocrystals,'' as was recently discussed by Co¨lfen and Antonietti (Angew. Chem. Int. Ed. 44 (2005) 5576). In contrast to most ''mesocrystals,'' which are generally polycrystalline in nature, each aggregate of (NH 4 ) 3 PW 12 O 40 is a characteristic porous single crystal. Furthermore, the micropores of (NH 4 ) 3 PW 12 O 40 are totally different from those found in other microporous crystals: zeolites have ''built-in'' pores defined by their crystal structure, while the (NH 4 ) 3 PW 12 O 40 nanocrystallites have none. Since (NH 4 ) 3 PW 12 O 40 micropores are continuous spaces as neighboring vacancies of the molecules, the shapes of the (NH 4 ) 3 PW 12 O 40 pores can in principle, assume various connectivities or networks within the crystal, and as such, are subsequently termed: ''sponge crystals.''

show abstract

Structure of Porous Aggregates of the Ammonium Salt of Dodecatungstophosphoric Acid, (NH₄)₃PW₁₂O₄₀: Unidirectionally Oriented Self-Assembly of Nanocrystallites

Cited by 77 publications

References 26 publications

Polymer synthesis by solid-acid catalyst based on heteropolyacid ammonium salt

Polymer synthesis by solid-acid catalyst based on heteropolyacid ammonium salt

Nanocatalysis: Mature Science Revisited or Something Really New?

“Sponge Crystal”: a novel class of microporous single crystals formed by self-assembly of polyoxometalate (NH4)3PW12O40 nanocrystallites

Contact Info

Product

Resources

About