Synthesis and Characterization of Polymer-Templated Mesoporous Silicas Containing Niobium

Abstract

A series of niobium-containing mesoporous silicas (Nb-MS) with different pore diameters has been synthesized via an acid-mediated route by using different kinds of nonionic triblock copolymers. The effect of the chain length of poly(propylene oxide) (PO) and poly(ethylene oxide) (EO) units on the structure of Nb-MS materials has been studied. The samples were characterized by X-ray diffraction (XRD), nitrogen adsorption, transmission electron microscopy (TEM), and temperature-programmed reduction (TPR). The pore diameter of Nb-MS increased with increasing the PO chain length in triblock copolymer. The microporosity was not affected by the type of the copolymer used.

“Hard” vs. “Soft” Templating Synthesis of Mesoporous Nb2O5 Catalysts for Oxidation Reactions

“…The cubic-type mesophases resulted from the application of poly(ethyleneoxide)-poly(propyleneoxide)-poly(ethyleneoxide) triblock copolymer (Pluronic F127, (EO) 106 (PO) 70 (EO) 106 ), whereas hexagonal mesophase were formed when Pluronic P123 ((EO) 20 (PO) 70 (EO) 20 )) was employed. Also, mesoporous niobium oxide with 3D-hexagonal structure was prepared by the same method but applying a triblock copolymer P85 (EO) 26 (PO) 39 (EO) 26 [33], whereas 2D-hexagonally ordered mesoporous niobium and tantalum mixed oxides were obtained when P123 triblock copolymer was used [34]. Another 3D-material of niobium, lithium niobate, was prepared by templating colloidal crystals of polyelectrolyte-coated spheres [35].…”

Multiple Functionalization of Mesoporous Silica in One‐Pot: Direct Synthesis of Aluminum‐Containing Plugged SBA‐15 from Aqueous Nitrate Solutions

“…[28] Apart from the incorporation of heteroatoms in the framework of siliceous SBA-15 materials, various methods of generating 'plugs' and/or 'constrictions' in the main mesopore of SBA-15 have also been recently developed for modification and/or adjustment of the pore structures of SBA-15. [29][30][31][32][33][34] 'Plugs'-containing SBA-15 material, usually referred to as plugged hexagonal templated silica (PHTS), was first explored by Van Der Voort et al by the method of introducing excessive silica source (TEOS) in the initial reaction mixture of SBA-15. [31] PHTS is the porous analogue of SBA-15, and it possesses the same two-dimensional (2D) hexagonal symmetry as SBA-15 but some of its cylindrical mesopores have internal porous plugs.…”

“…[32,33] Therefore, it has a relatively higher micropore volume and a higher stability than regular SBA-15, which makes this material very promising. [34] Although the coexistence of combined meso-and micropores is one of the interesting properties of SBA-15, [35] plugged SBA-15 materials with increased micropores and pore wall thickness will offer unusual advantages such as improved hydrothermal stability, multifunctionality to process a large variety of feedstocks, capability to encapsulate waste in the micropores, controlled leaching rates for a constant and gradual release of an active component, etc. [31b] In general, PHTS is synthesized by using a high amount of TEOS (TEOS/ P123 larger than 59), and it can even be synthesized under high stirring temperature.…”

“…[31b] In general, PHTS is synthesized by using a high amount of TEOS (TEOS/ P123 larger than 59), and it can even be synthesized under high stirring temperature. [34] No PHTS is obtained when using the normal amount of TEOS (TEOS/P123 = 59) for the conventional synthesis of SBA-15. Furthermore, structurally integral SBA-15 can be synthesized under slightly high pH (2)(3)(4)(5) conditions by pre-hydrolyzing the TEOS.…”

Adsorption properties of ordered mesoporous silicas synthesized in the presence of block copolymer Pluronic F127 under microwave irradiation

“…This important finding opened new perspectives for the development and applications of nanomaterials as well as stimulated further advancements in nanoscience and nanotechnology (Van Der Voort et al 2008;Ciesla and Schuth 1999;Sayari and Hamoudi 2001;Oye et al 2001;Stein 2003;Taguchi and Schuth 2005;Cejka and Mintova 2007;Izqierdo-Barba et al 2008;Ispas et al 2009;Jaroniec et al 1998;Nowak et al 2004;Kruk et al 2002b). There is a wide interest in OMSs, especially those with organic functionalities, which can be synthesized by using commercially available organosilanes in the presence of structure directing agents such as ionic surfactants Asefa et al 1999;Jaroniec 1999, 2000;Kruk et al 2002b;Lim and Stein 1999), neutral surfactants and non-ionic block copolymers (Olkhovyk and Jaroniec 2005b;Grudzien et al 2006aGrudzien et al , 2006b.…”