Polyoxometalate (POM)-mediated cluster catalysis has emerged as a promising strategy for the development of efficient and selective catalysts because of its unique advantages in activity modulation, interface engineering, and electron/proton transfer. In this study, a series of sub-nanowire hybrid catalysts (denoted as Pd-PMo_12−xV_x, x = 0–3) is successfully constructed via a self-assembly strategy involving Keggin-type POMs and Pd⁰ clusters. Among them, Pd-PMo₁₀V₂ exhibits excellent catalytic performance for the selective hydrogenation of phenol to cyclohexanone, achieving 99.9% phenol conversion and 95.4% product selectivity. Experimental results demonstrate that POMs not only effectively stabilize sub-nano Pd⁰ clusters but also modulate their electronic structures, thereby enhancing the catalytic activity. Compared with tungsten-based POMs, molybdenum-based analogs exhibit stronger reducibility and superior electron/proton acceptance capabilities, which provide more efficient active hydrogen transfer channels for multi-hydrogenation processes. Moreover, increasing the reaction temperature can help overcome the energy barrier associated with the electron-coupled proton transfer process, thereby enabling the full utilization of redox active sites within POMs. This work provides a novel design strategy and mechanistic insight for the development of highly active and selective noble-metal cluster catalysts.

Clusters exhibit unique activity and selectivity in catalysis. However, research on the interactions between clusters and their synergistic catalysis is still in its infancy. Herein, ultrafine sub-nanowires composed of Pd⁰ sub-nanoclusters and polyoxometalates (POMs) stacked by cluster–cluster are successfully constructed (abbreviated as Pd-POMs). Notably, Pd-PW₁₂ exhibits exceptional activity (99%) and selectivity (99%) for the hydrogenation of C=C bonds in 4-vinylbenzaldehyde, significantly outperforming other supported Pd-based catalysts. Density functional theory (DFT) calculation results indicate that POMs can stabilize and adjust the electronic structure of Pd clusters, promoting the specific adsorption and reducing hydrogenation energy barriers of C=C bonds. Moreover, the electron–coupled proton (e⁻/H⁺) transfer process at the interface can be regulated by altering the redox properties of POMs, achieving extra regulations of the catalytic activity. This work reveals the synergistic optimization effects of POMs on the activity and selectivity of Pd clusters, providing new insights into the rational design of highly efficient catalysts.

The development of novel proton exchange membranes (PEMs) with high proton conductivity and good mechanical performance as alternatives to Nafion is crucial. Polyoxometalates (POMs), a type of solid-state nanoclusters, possess high proton conductivity and good structural stability, making them suitable functional inorganic fillers to improve the performance of PEMs. Herein, the Keggin-type POM H₃PW₁₂O₄₀·nH₂O (PW₁₂) was introduced into sulfonated polyaryletherketone (SPAEK) with closely packed and flexible side chains to construct hybrid membranes (SPAEK-PW₁₂-x%, x = 5, 10, 13, 15). Because of its structural characteristics, the nanosized PW₁₂ induced precise hybridization of the nanophase structure of this ionomeric polymer and the formation of proton transport channels. Additionally, the hydrogen-bonding networks formed by PW₁₂ and sulfonic acid groups increased the proton conductivity and mechanical strength of the resulting hybrid PEMs and improved the close-packed structure of the PEMs to achieve an appropriate balance between conductivity and fuel permeation. In particular, SPAEK-PW₁₂-13% achieved an enhanced proton conductivity of 0.167 S∙cm⁻¹ at 80 °C, which was 2.2 times greater than that of the pristine membrane. Moreover, the mechanical properties, chemical stability, resistance to methanol penetration, and ionic selectivity of the hybrid membrane were significantly improved upon addition of a moderate amount of PW₁₂. This work provides an approach for the design and development of new-generation organic–inorganic hybrid membranes through precise hybridization of POMs.

Solar vapor generation (SVG) represents a promising technique for seawater desalination to alleviate the global water crisis and energy shortage. One of its main bottleneck problems is that the evaporation efficiency and stability are limited by salt crystallization under high-salinity brines. Herein, we demonstrate that the 3D porous melamine-foam (MF) wrapped by a type of self-assembling composite materials based on reduced polyoxometalates (i.e. heteropoly blue, HPB), oleic acid (OA), and polypyrrole (PPy) (labeled with MF@HPB-PPy_n-OA) can serve as efficient and stable SVG material at high salinity. Structural characterizations of MF@HPB-PPy_n-OA indicate that both hydrophilic region of HPBs and hydrophobic region of OA co-exist on the surface of composite materials, optimizing the hydrophilic and hydrophobic interfaces of the SVG materials, and fully exerting its functionality for ultrahigh water-evaporation and anti-salt fouling. The optimal MF@HPB-PPy₁₀-OA operates continuously and stably for over 100 h in 10 wt% brine. Furthermore, MF@HPB-PPy₁₀-OA accomplishes complete salt-water separation of 10 wt% brine with 3.3 kg m⁻² h⁻¹ under 1-sun irradiation, yielding salt harvesting efficiency of 96.5%, which belongs to the record high of high-salinity systems reported so far and is close to achieving zero liquid discharge. Moreover, the low cost of MF@HPB-PPy₁₀-OA (2.56 ＄ m⁻²) suggests its potential application in the practical SVG technique.