One-pot synthesis of hierarchical porous layered hybrid materials based on aluminosilicate sheets and organic functional pillars

Abstract

Layered hybrid materials (LHMs) based on ordered silicoaluminate sheets linked with organic fragments, perpendicularly located and stabilized in the interlayer space, were synthesized by one-pot direct hydrothermal process, in absence of structural directing agents (SDAs), and using bridged silsesquioxanes as organosilicon precursors. By following the synthesis described here, the preliminary preparation of inorganic layered precursors, post-synthesis swelling and/or pillaring treatments can be avoided. The physico-chemical and structural characteristics of the materials were studied by chemical and thermogravimetrical analyses, X-ray diffraction, TEM microscopy, spectroscopic techniques (NMR and FTIR) and textural measurements. The complete exchange of intracrystalline sodium cations by protons, without substantial structural alteration of hybrid materials, facilitated the generation of hybrid materials, which contained acid and base sites located in the inorganic (silicoaluminate layers) and in the organic interlayer linkers, respectively, being the resultant acid-base materials active and selective catalysts.

Organic‐Inorganic Hybrid Materials: Multi‐Functional Solids for Multi‐Step Reaction Processes

“…Furthermore, these lamellar hybrids should allow the combination of intrinsic active sites, associated to the organic and inorganic counterparts present in the framework, and those externally incorporated onto the surface of inorganic sheets by grafting, tethering, or simple deposition . Recently, direct one‐step hydrothermal synthesis routes have been developed to prepare pillared hybrid materials, avoiding long and expensive post‐synthesis treatments, modifying conventional lamellar inorganic precursors, and without using sophisticated swelling or intercalation agents . In these type of solids, so‐called Layered Hybrid Materials (LHMs), the synthesis gel was formed with high aluminum content and in the presence of bridged silsesquioxanes as the only organosilicon source.…”

“…[42] Recently,d irect one-step hydrothermal synthesis routes have been developed to preparep illared hybridm aterials, avoiding long and expensive post-synthesis treatments, modifying conventional lamellar inorganic precursors, and without using sophisticateds welling or intercalation agents. [43] In these type of solids, so-called Layered Hybrid Materials (LHMs), the synthesis gel was formed with high aluminum content andi nt he presence of bridgeds ilsesquioxanes as the only organosilicons ource.T he result is the direct synthesis of hybrid catalysts based on organizedp iled aluminosilicate layers,c ovalently linked between them by specific functional organic bridges. Advances performed with these materials made possible the preparation of non-connectedi ndividual (organo)silicoaluminate layers with different spatial organization by the use of severalo rgano(mono)siloxanes duringt he hydrothermals ynthesis process.…”

“…Lamellar hybrid material containinga cid and base sites formed by the direct assembly of functionalized (organo)aluminosilicate nanosheets. Figure adapted from refs [43]. and[44].…”

Catalytic use of layered materials for fine chemical syntheses

“…Layered hybrid materials based on ordered silicoaluminate sheets linked with organic pillars in the interlayer space were synthesized by a one-pot direct hydrothermal process without the need for initial swelling and/or pillaring the layered inorganic precursors. 113 Upon facile exchange of intracrystalline sodium cations with protons, localised acid centres were formed contributing to excellent catalytic activities in Knoevenagel condensations between ethylcyanoacetate and various aldehydes (Scheme 25). The hydrothermal processes were later extended to the synthesis of bifunctional acid-base hybrid materials based on ordered organic aluminosilicate sheets with amino and sulfonic groups located in the interlayer space.…”

Expandable Layered Hybrid Materials Based on Individual 1D Metalorganic Nanoribbons

“…Layered metallic oxides (titanates, vanadates, molybdates, etc. ), clays (such as montmorillonite), anionic clays (layered double hydroxides, LDHs) or silicoaluminates (such as magadiite or kenyaite) are representative families of layered solids based on the regular and homogeneous ordered distribution of inorganic sheets [3,4,5,6,7].…”