Polyoxometalate‐Soft Matter Composite Materials: Design Strategies, Applications, and Future Directions

Abstract

Molecular metal oxides, or polyoxometalates (POMs) offer unrivalled properties in areas ranging from catalysis and energy conversion through to molecular electronics, biomimetics and theranostics. While POMs are ubiquitous metal oxide model systems studied in most areas of chemistry and materials science, their technological deployment is often hampered by their molecular nature, as this leads to increased degradation, leaching and loss of reactivity, particularly when harsh applications, such as water electrolysis, thermal catalysis or highly basic/acidic reaction solutions are targeted. Therefore, immobilization of POMs on heterogeneous substrates has recently become a central theme in POM research. While early studies focused mainly on metal oxide and semiconductor supports, more recently, POM integration in soft matter matrices including polymers, conductive polymers, hydrogels and stimuliresponsive matrices have led to breakthroughs in multifunctional composite design. This Progress Report will summarize the recent pioneering studies in this emerging field, highlight current challenges which need to be overcome to allow a more widespread technological deployment and provide the authors' view of some of the most promising future directions of the research field. In addition, we provide an unprecedented summary of the correlations between structure (on the molecular, nano-and microscale) and resulting reactivity, so that materials design beyond empirical studies can be further developed. We believe that this timely Progress Report will serve as a focal point to further develop the field, as well as point of reference for newcomers in the area of knowledge-driven bottom up materials design. Given this broad range of interest groups, we believe that Advanced Functional Materials is the ideal journal for this Progress Report.

Controllable Transition Metal-Directed Assembly of [Mo2O2S2]2+ Building Blocks into Smart Molecular Humidity-Responsive Actuators

“…The transmission electron microscopy image shows that the { Bi 8 Mo 48 } particles are dispersed in the composite without serious agglomeration (Figure S16). In addition, the solid-state 31 P NMR in Figure b also proves that { Bi 8 Mo 48 } retains its structure during the composite formation, and the chemical shifts of { Bi 8 Mo 48 } (δ 1 = +28.22 ppm, δ 2 = +23.75 ppm) are substantially consistent with those of Bi 8 Mo 48 -PDDA (δ 3 = +29.27 ppm, δ 4 = +23.73 ppm).…”

“…The transmission electron microscopy image shows that the {Bi 8 Mo 48 } particles are dispersed in the composite without serious agglomeration (Figure S16). 43 In addition, the solidstate 31 Humidity-Driven Actuation of the Bi 8 Mo 48 -PDDA/ PVDF Bilayer Film. Furthermore, the as-pressed Bi 8 Mo 48 -PDDA film was further coupled with a commercial hydrophobic PVDF film by the lamination method under 2 MPa pressure, and the two layers were tightly bound together without delamination (Figures S12 and S13).…”

Advanced Formulations Based on Poly(ionic liquid) Materials for Additive Manufacturing

“…Our group has demonstrated, for the first time, the possibility of successfully designing functional advanced multi-materials and devices based on PILs with embedded hybrid organic–inorganic polyoxometalates (POMs). POMs are self-assembled large mixed metal oxides, typically composed of W, Mo, and V. They possess an unusually large size for inorganic molecules and an array of interesting physico-chemical properties, including redox, catalytic, and photochromism [ 191 , 192 , 193 ]. This work exemplified how the unique photo/redox properties of nanostructured POMs could be translated into a macroscopic material using DLP, as shown Figure 7 .…”

Exploring the Reactivity of Polyoxometalates toward Proteins: From Interactions to Mechanistic Insights

“…1,2 Hence, research areas addressing the synergy between metallic clusters and proteins are rapidly growing due to their potential in the development of new types of drugs, 3,4 sensors, 5,6 artificial enzymes, 7,8 and novel biomaterials. 9,10 Metal-oxo clusters in particular are one of the most diverse and versatile groups among the many families of metallic clusters. 11 These clusters can be anionic or cationic in nature.…”

“…Moreover, these hybrid systems serve important biological functions in living organisms, playing a key role in vital biochemical transformations, typically in combination with proteins. Clear examples of this are the CaMn 4 O 5 metal-oxo core of photosystem II, which catalyzes water-splitting during photosynthesis in certain organisms, and iron–sulfur clusters, which act as protein cofactors in many biochemical processes. , Hence, research areas addressing the synergy between metallic clusters and proteins are rapidly growing due to their potential in the development of new types of drugs, , sensors, , artificial enzymes, , and novel biomaterials. , …”