Microporous Aluminoborates with Large Channels: Structural and Catalytic Properties

Abstract

Channel zapping: PKU-1 and newly synthesized PKU-2 (Al(2)B(5)O(9)(OH)(3)⋅n H(2)O; see picture) possess microporous structures with 18-ring and 24-ring channels, respectively. They show high reactivity and size selectivity in the cyanosilylation of aldehydes as heterogeneous Lewis acid catalysts. The different channel sizes determine the substrate selectivity. These examples demonstrate the potential of octahedron-based aluminoborate channels in catalysis.

A Series of Aluminoborates Templated or Supported by Zinc–Amine Complexes

“…The large pores of PKU-2 contain 24 edge-sharing AlO 6 octahedra, andB 2 O 5 and B 3 O 7 units attach to the walls of AlÀOb ackbones. [6] The channels built by BÀOÀBb onds are also known;N azar andc o-workers obtained an ew cobalt borate with at unnels tructurec onsisting of B 3 O 7 and B 4 O 9 units, and metali ons located in the small pockets of BÀOn etwork. [7] In addition, mesoporous vanadoborate has been made by employing the scale chemistryt heory with nanosized MÀOÀBclusters.…”

“…[4] Recent interests have been focused on the open-framework metal borates, extending their uses in catalysis and ion-exchange processes. [5][6][7][8][9] Ac ommon structuralf eature of these open-framework structures is the strict alternation of oxo boron clusters and metal (M) centers. An illustrativee xample is NDTB-1,w ith an unusual super-tetrahedral3 Dcationic framework containing crown-like B 10 O 24 groups and thorium ions, [5] which has shown superb anion-exchange capabilities.…”

“…[10][11][12] Since 2003, the molten boric acid flux methodh as been extensively studied to make open-framework ABOs (PKUn), the detailed structures of PKU-1,P KU-2,P KU-5, PKU-6 and PKU-8w ere established by using powder X-ray diffraction techniques. [6,13] Recently,w eh ave focusedo nt he hydro(solvo)thermal synthesis of open-framework ABOs using Al(iPrO) 3 as Al source, which promotes the growth of good-qualitys ingle crystalsa nd has led to greata dvances in systemso fi norganic cation-,o rganic amine-, and metal complex-templated ABOs. [14,15] These open-framework materials integrate the uniform porosity of zeolites with the extraordinaryo ptical properties of metal borates.…”

PKU-3: An HCl-Inclusive Aluminoborate for Strecker Reaction Solved by Combining RED and PXRD

“…10−19 When weakly interacted species such as H 3 BO 3 , H 2 O are involved in the channels, the obtained aluminoborates are stable after calcination and can be used as catalysts in different reactions. 13,16,20 Unfortunately, aluminoborates synthesized with weakly interacted guest species normally crystallized in small sizes, and most of their structures were difficult to be elucidated by single crystal X-ray diffraction (SC-XRD). 16 17,18,21,22 One typical example is PKU-3 in this work, which was synthesized more than 10 years ago without a structure model.…”

“…13,16,20 Unfortunately, aluminoborates synthesized with weakly interacted guest species normally crystallized in small sizes, and most of their structures were difficult to be elucidated by single crystal X-ray diffraction (SC-XRD). 16 17,18,21,22 One typical example is PKU-3 in this work, which was synthesized more than 10 years ago without a structure model. The sample shows preferred orientation with a needle-like morphology, and the severe peak overlapping due to the trigonal symmetry (P3̅ c1) and relatively large unit cell dimensions.…”