Engineering polyoxometalates with emergent properties

Abstract

Polyoxometalates are clusters of metal-oxide units, comprising a large diversity of nanoscale structures, and have many common building blocks; in fact polyoxometalate clusters are perhaps the largest non-biologically derived molecules structurally characterised. Not only can polyoxometalates have gigantic nanoscale molecular structures, but they also a have a vast array of physical properties, many of which can be specifically 'engineered-in'. Here we describe how building block libraries of polyoxometalates can be used to construct systems with important catalytic, electronic, and structural properties. We also show that it is possible to construct complex chemical systems based upon polyoxometalates, manipulating the templating/self templating rules to exhibit emergent processes from the molecular to the macroscopic scale.

Classical Keggin Intercalated into Layered Double Hydroxides: Facile Preparation and Catalytic Efficiency in Knoevenagel Condensation Reactions

“…They are constructed via a condensation reaction between their metal oxide polyhedra (MOx: M = W VI , Mo VI , V V , Nb V , Ta V , etc., and x = 4-7) bridged together in a corner-, edge-, or rarely in a face-shared fashion. [1][2][3] POMs found to be very attractive systems due to their fascinating properties which can be finely tuned by appropriate choice of metal ion(s), heteroatoms and counter ions. [4][5][6] One the POMs' important properties is their superior catalytic performance in numerous processes which has been exploited in industrial processes.…”

Gas-Phase Fragmentation Pathways of Mixed Addenda Keggin Anions: PMo12-nWnO403– (n = 0–12)

“…Scheme 1 shows the structure of the Mo 12 POM ion reported in our previous study [34]. For simplicity, we will hereafter use the number of Mo and W atoms in the structure to represent the triply charged POM anions (e.g., PMo 6 12 POM molar ratios of 3:9, 6:6, and 9:3. An ESI mass spectrum obtained by mixing equal volumes of all three solutions is shown in Figure 1.…”

“…Introduction P olyoxometalates (POMs) are a class of inorganic materials that are of interest for a variety of applications because of their remarkable redox, photochemical, and magnetic properties [1][2][3][4][5][6][7][8][9]. The Keggin POM [10], a class of stable, redox-active, triply-charged anions comprised of a metal-oxide cage structure (M 12 O 36 ; M = early transition metal) with an internal XO 4 n-group (typically X = Si, P; n = 4, 3, respectively), is one of the most widely studied POM systems.…”

Solvent-Free Biginelli Reactions Catalyzed by Hierarchical Zeolite Utilizing a Ball Mill Technique: A Green Sustainable Process

“…The utilization of solid heteropolyacids (HPAs) as alternative heterogeneous catalysts for conventionally homogenous analogs, such as hydrofluoric and sulfuric acids, has been well known for many years [25]. However, HPAs, which are utilized as an acid catalyst for the transformation reactions [26], suffer from their recovery and reuse in presence of water and organic solvents [27,28]. To overcome these drawbacks, heterogenization of HPAs into different host supports like silica [29] and activated carbon [30] were selectivity with minimal waste amounts.…”

“…The utilization of solid heteropolyacids (HPAs) as alternative heterogeneous catalysts for conventionally homogenous analogs, such as hydrofluoric and sulfuric acids, has been well known for many years [25]. However, HPAs, which are utilized as an acid catalyst for the transformation reactions [26], suffer from their recovery and reuse in presence of water and organic solvents [27,28]. To overcome these drawbacks, heterogenization of HPAs into different host supports like silica [29] and activated carbon [30] were The commonly-used homogeneous catalysts for Biginelli reactions, such as BF 3 ·Et 2 O, InCl 3 , LaCl 3 , Sr(NO 3 ) 2 , and ceric ammonium nitrate have several drawbacks, such as separation difficulties, recovery processes, pre-used catalyst's disposal, toxicity and corrosion [20][21][22][23][24].…”