Directional Shunting of Photogenerated Carriers in POM@MOF for Promoting Nitrogen Adsorption and Oxidation

Boosting CO2 photoreduction over perovskite quantum dots decorated with dispersed ruthenium nanoparticles

High efficiency CO2 conversion materials are ideal for solar to carbon fuel conversion. Halide perovskite quantum dots (QDs) are highly desirable as catalysts and have been extensively investigated in the field of CO2 photoreduction. The major challenge lies in the severe charge recombination and the weak ability to activate CO2. Herein, we have identified dispersed Ru nanoparticles anchored on CsPbBr3 (CPB) QDs as prospective photocatalysts for CO2 reduction at ambient pressure with light irradiation. The optimized 0.45 % CPB@Ru reduced CO2 to CO at a rate of 28.12 μmol g-1 h-1 without any sacrificial agent and co-catalysts, about 4 times higher than that of the CPB QDs (7.03 μmol g-1 h-1). Experiments and DFT calculations reveal that the as-prepared CPB@Ru showed increased photogenerated charge separation, CO2 adsorption/activation and lower energy barriers for the formation of *COOH intermediate, which are crucial for enhancing the photocatalytic CO2 reduction activity. This work provides a convenient pathway for designing high-performance perovskite photocatalysts with high selectivity and high catalytic activity using metal nanoparticle loading technology.

Lattice Distortion Broadens the eg Band of Co3O4 to Facilitate p-d Hybridization for Enhanced Electrochemical Nitrate Synthesis

The electrochemical nitrogen oxidation reaction (NOR) presents a sustainable pathway for nitrate synthesis under mild conditions; however, the process is hindered by the inadequate adsorption and activation of N2 on electrocatalysts. In this study, we utilized Co3O4 as a model catalyst and engineered lattice distortions by introducing oxygen vacancies, which expanded the eg band of the active sites to enhance N2 activation. The modified Co3O4 catalyst achieved a Faradaic efficiency of 10.68% and a nitrate yield of 58.80 μg·h-1·mgcat-1. Comprehensive experimental and density functional theory (DFT) analyses demonstrated that these modifications resulted in a shortened Co-N bond length and an elongated N≡N bond, leading to improved p-d hybridization between N2 and Co sites. Moreover, the enhancements in catalytic performance were also attributed to the improved electron transfer properties stemming from the altered band structure of Co3O4. This work provides innovative design principles for catalysts aimed at facilitating complex electrocatalytic reactions with multiple kinetics.

Dual Regulation of Sensitizers and Cluster Catalysts in Metal-Organic Frameworks to Boost H2 Evolution

Photocatalytic efficiency is closely correlated to visible-light absorption ability, electron transfer efficiency and catalytic center activity of photocatalysts, nevertheless, the concurrent management of these factors to improve photocatalytic efficiency remains underexplored. Herein, we proposed a sensitizer/catalyst dual regulation strategy on the polyoxometalate@Metal-Organic Framework (POM@MOF) molecular platform to construct highly efficient photocatalysts. Impressively, Ni-Sb9@UiO-Ir-C6, obtained by coupling strong sensitizing [Ir(coumarin 6)2(bpy)]+ with Ni-Sb9 POM with extremely exposed nickel site [NiO3(H2O)3], can drive H2 evolution with a turnover number of 326923, representing a record value among all the POM@MOF composite photocatalysts. This performance is over 34 times higher than that of the typical Ni4P2@UiO-Ir constructed from [Ir(ppy)2(bpy)]+ and Ni4P2 POM. Systematical investigations revealed that dual regulation of sensitizing and catalytic centers endowed Ni-Sb9@UiO-Ir-C6 with strong visible-light absorption, efficient inter-component electron transfer and high catalytic activity to concurrently promote H2 evolution. This work opens up a new avenue to develop highly active POM@MOF photocatalysts by dual regulation of sensitizing/catalytic centers at the molecular level.

Activation of Bi2MoO6/Zn0.5Cd0.5S charge transfer through interface chemical bonds and surface defects for photothermal catalytic CO2 reduction

The photocatalytic reduction of CO2 to high-value fuels has been proposed as a solution to the energy crisis caused by the depletion of energy resources. Despite significant advancements in photocatalytic CO2 reduction catalyst development, there are still limitations such as poor CO2 adsorption/activation and low charge transfer efficiency. In this study, we employed a defect-induced heterojunction strategy to construct atomic-level interface Cd-O bonds and form Bi2MoO6/Zn0.5Cd0.5S heterojunctions. The sulfur vacancies (VS) formed in Bi2MoO6/Zn0.5Cd0.5S acted as activation sites for CO2 adsorption. While the interfacial stability provided by the Cd-O bonds served as an electron transfer channel that facilitated the movement of electrons from the interface to the catalytic site. The VS and Cd-O bonds simultaneously influence the distribution of charge, inducing the creation of an interface electric field that facilitates the upward displacement of the center of the d-band. This enhances the adsorption of reaction intermediates. The optimized Bi2MoO6/Zn0.5Cd0.5S heterostructure exhibited high selectivity and stability of photoelectrochemical properties for CO, generating 42.97 μmol⋅g-1⋅h-1 of CO, which was 16.65-fold higher than Zn0.5Cd0.5S under visible light drive. This research provides valuable insights for designing photocatalyst interfaces with improved CO2 adsorption conversion efficiency.

A Sucker-Reactor Polyoxometalate Assembled Superstructures for Efficient Photocatalytic Nitrogen Fixation

Designing a reaction system that integrates reactant capture and transformation in an artificial photosynthesis system to achieve high reaction efficiency remains challenging. Here, an ionic liquid (IL) -polyoxometalate (POM) superstructure photocatalyst (P2HPMo) is reported, where the anisotropy of the superstructure is allowed by adjusting the alkyl chain lengths of ILs. Experimental data and theoretical simulation show that ILs and POM serve as the "sucker" and "reactor" of the reaction system to capture and transform the reactants, respectively. In particular, the addition of quaternary phosphorous IL cations is not only conducive to the adsorption of N2 but also effectively promotes the activation of N2 by manipulating the energy band and electronic structure. Consequently, the synthesized P2HPMo exhibits an ammonia synthesis rate of 98 µmol·gcat -1·h-1, which is one of the highest values available in a sacrificial agent-free system.

Development of polyoxometalate-loaded MOFs for heterogeneous catalysis and enhanced dye adsorption

This study focuses on the enhancement of MIL-117 functionality by incorporating a well-known polyoxometalate (POM), tetrabutylammonium octamolybdate [(n-C4H9)4N]4[Mo8O26]. Using an encapsulation method with conventional heating, Mo8O264- anions were for the first time successfully integrated into MIL-117 tubular channels (Mo8O26@MIL-117). Comprehensive characterization of the material through FTIR, XRD, BET, FE-SEM, EDX, and XPS confirmed the uniform distribution of Mo8O264- within MIL-117 without compromising its structural integrity. The Mo8O26@MIL-117 composite demonstrates exceptional catalytic performance in oxidative C-N bond formation and Paal-Knorr pyrrole synthesis, achieving high yields under optimized conditions with diverse amine substrates. Characterization and stability assessments confirm Mo8O26@MIL-117 as a robust and recyclable catalyst, maintaining structural integrity and catalytic activity over multiple cycles, highlighting its potential for sustainable applications in synthetic chemistry. The composite material was also evaluated for its efficacy in dye removal, specifically targeting methylene blue (MB) and Rhodamine B (RHB) from aqueous solutions. Mo8O26@MIL-117 exhibited superior adsorption capacity for MB compared to MIL-117 alone, demonstrating high efficiency even at elevated concentrations. The composite showed improved selectivity towards MB over RHB, highlighting its potential for selective dye removal in wastewater treatment applications.

Recent Advances in Metal-Organic Frameworks and Their Derivatives for Adsorption of Radioactive Iodine

Radioactive iodine (131I) with a short half-life of ~8.02 days is one of the most commonly used nuclides in nuclear medicine. However, 131I easily poses a significant risk to human health and ecological environment. Therefore, there is an urgent need to develop a secure and efficient strategy to capture and store radioactive iodine. Metal-organic frameworks (MOFs) are a new generation of sorbents with outstanding physical and chemical properties, rendering them attractive candidates for the adsorption and immobilization of iodine. This review focuses on recent research advancements in mechanisms underlying iodine adsorption over MOFs and their derivatives, including van der Waals interactions, complexing interactions, and chemical precipitation. Furthermore, this review concludes by outlining the challenges and opportunities for the safe disposal of radioactive iodine from the perspective of the material design and system evaluation based on our knowledge. Thus, this paper aims to offer necessary information regarding the large-scale production of MOFs for iodine adsorption.

Enhanced photocatalytic U(VI) reduction via double internal electric field in CoWO4/covalent organic frameworks p-n heterojunction

Photoreduction of highly toxic U(VI) to less toxic U(IV) is crucial for mitigating radioactive contamination. Herein, a CoWO4/TpDD p-n heterojunction is synthesized, with TpDD serving as the n-type semiconductor substrate and CoWO4 as the p-type semiconductor grown in situ on its surface. The Fermi energy difference between TpDD and CoWO4 provides the electrochemical potential for charge-hole separation. Moreover, the Coulombic forces from the distinct carrier types between the two materials synergistically facilitate the transfer of electrons and holes. Hence, an internal electric field directed from TpDD to CoWO4 is established. Under photoexcitation conditions, charges and holes migrate efficiently along the curved band and internal electric field, further enhancing charge-hole separation. As a result, the removal capacity of CoWO4/TpDD increases from 515.2 mg/g in the dark to 1754.6 mg/g under light conditions. Thus, constructing a p-n heterojunction proves to be an effective strategy for remediating uranium-contaminated environments.

Modulating charge oriented accumulation via interfacial chemical-bond on In2O3/Bi2MoO6 heterostructures for photocatalytic nitrogen fixation

Photocatalytic nitrogen fixation presents an eco-friendly approach to converting atmospheric nitrogen into ammonia (NH3), but the process faces challenges due to rapid interface charge recombination. Here, we report an innovative charge transfer and oriented accumulation strategy using an In-O-Mo bond-modulated S-scheme heterostructure composed of In2O3/Bi2MoO6 (In/BMO) synthesized using a simple electrostatic assembly. The unique interfacial arrangement with optimal photocatalyst configuration (3 % In/BMO) enabled enhanced photogenerated electron separation and transfer, leading to a remarkable nitrogen fixation rate of approximately 150.9 μmol·gcat-1·h-1 under visible light irradiation. The performance of the photocatalyst was 9-fold and 27-fold higher than that of its pristine components, Bi2MoO6 and In2O3, respectively. The experimental and theoretical evaluation deemed interfacial In-O-Mo bonds crucial for rapid transfer and charge-oriented accumulation. Whereas the generated internal electric field drove the spatial separation and transfer of photo-generated electrons and holes, significantly enhancing the photocatalytic N2-to-NH3 conversion efficiency. The proposed work lays the foundation for designing S-scheme heterostructures with highly efficient interfacial bonds, offering a promising avenue for substantial improvements in photocatalytic nitrogen fixation.

Construction of Fe(III) Active Sites on Phenanthroline-Grafted g-C3N4: Reduced Work Function and Enhanced Intramolecular Charge Transfer for Efficient N2 Photofixation

Photocatalytic nitrogen fixation is one of the important pathways for green and sustainable ammonia synthesis, but the extremely high bonding energy of the N≡N triple bond makes it difficult for conventional nitrogen fixation photocatalysts to directly activate and hydrogenate. Given this, we covalently grafted the phenanthroline unit onto graphitic carbon nitride nanosheets (CN) by the simple thermal oxidation method and complexed it with transition metal Fe3+ ions to obtain stable dispersed Fe active sites, which can significantly improve the photocatalytic activity. The Fe(III)-4-P-CN photocatalyst morphology consists of porous lamellar structures internally connected by nanowires. The special morphology of the catalysts gives them excellent nitrogen fixation performance, with an average NH3 yield of 492.9 μmol g-1 h-1, which is 6.5 times higher than that of the pristine CN, as well as better photocatalytic cycling stability. Comprehensive experiments and density-functional theory results show that Fe(III)-4-P-CN is more favorable than pristine CN for *N2 activation, effectively lowering the reaction energy barrier. Moreover, other byproducts (such as nitrate and H2O2) are also produced during the photocatalytic nitrogen fixation process, which also provides a new way for nitrogen-fixing photocatalysts to achieve multifunctional applications.

Selective Electrocatalytic Conversion of Nitric Oxide to High Value-Added Chemicals

The artificial disturbance in the nitrogen cycle has necessitated an urgent need for nitric oxide (NO) removal. Electrochemical technologies for NO conversion have gained increasing attention in recent years. This comprehensive review presents the recent advancements in selective electrocatalytic conversion of NO to high value-added chemicals, with specific emphasis on catalyst design, electrolyte composition, mass diffusion, and adsorption energies of key intermediate species. Furthermore, the review explores the synergistic electrochemical co-electrolysis of NO with specific carbon source molecules, enabling the synthesis of a range of valuable chemicals with C─N bonds. It also provides in-depth insights into the intricate reaction pathways and underlying mechanisms, offering valuable perspectives on the challenges and prospects of selective NO electrolysis. By advancing comprehension and fostering awareness of nitrogen cycle balance, this review contributes to the development of efficient and sustainable electrocatalytic systems for the selective synthesis of valuable chemicals from NO.

Schottky Junctions with Bi@Bi2MoO6 Core-Shell Photocatalysts toward High-Efficiency Solar N2-to-Ammonnia Conversion in Aqueous Phase

The photocatalytic nitrogen reduction reaction (NRR) in aqueous solution is a green and sustainable strategy for ammonia production. Nonetheless, the efficiency of the process still has a wide gap compared to that of the Haber-Bosch one due to the difficulty of N2 activation and the quick recombination of photo-generated carriers. Herein, a core-shell Bi@Bi2MoO6 microsphere through constructing Schottky junctions has been explored as a robust photocatalyst toward N2 reduction to NH3. Metal Bi self-reduced onto Bi2MoO6 not only spurs the photo-generated electron and hole separation owing to the Schottky junction at the interface of Bi and Bi2MoO6 but also promotes N2 adsorption and activation at Bi active sites synchronously. As a result, the yield of the photocatalytic N2-to-ammonia conversion reaches up to 173.40 μmol g-1 on core-shell Bi@Bi2MoO6 photocatalysts, as much as two times of that of bare Bi2MoO6. This work provides a new design for the decarbonization of the nitrogen reduction reaction by the utilization of renewable energy sources.

2,5-Thiophenedicarboxylic Acid Bridging Hexameric CeIII-Substituted Selenotungstate and Its Application for Detecting Mucin 1

The development of polyoxometalate chemistry not only is derived from the continuous discovery of novel polyoxometalates (POMs) but also stems from the exploitation of their new functionalities. In this work, we obtained a rigid sulfur-containing heterocyclic ligand-linking aggregate [N(CH3)4]10Na6H6[Ce8(H2O)26W8(HTDA)2(TDA)2O20][SeW4O18]2[SeW9O33]4·112H2O (1) (H2TDA = 2,5-thiophenedicarboxylic acid). Its polyanionic unit consists of one [Ce4(H2O)13W4O10(HTDA)(TDA)O10]18+ cluster and two kinds of Keggin-type [SeW4O18] and [SeW9O33] segments. It is noteworthy that H2TDA ligands not only work as connectors to link two symmetrical {[Ce4(H2O)13W4(HTDA)(TDA)O10][SeW4O18][SeW9O33]2}11- units but also function as ornaments to graft to the polyanionic backbone. Furthermore, 1 and 3,4-ethylenedioxythiophene (EDOT) were deposited on the glassy carbon electrode (GCE) by the electropolymerization (EPM) method, resulting in a 1-poly(3,4-ethylenedioxythiophene) (1-PEDOT) composite film, which can provide sufficient binding sites to immobilize Au nanoparticles (Au NPs). Hereafter, the Au NPs-immobilized 1-PEDOT modified electrode (Au/1-PEDOT/GCE) was used to construct an electrochemical aptasensor to detect mucin 1, showing a low detection limit of 29.5 fM in the Tris solution. This work not only demonstrates that rigid heterocyclic ligands are beneficial for the creation of novel rare-earth-substituted selenotungstate hybrids but also provides more enlightenment for POM-based materials used for electrochemical detection of cancer markers.

Drawing Inspiration from Nature: Trinitarian Strategies for Designing Polyoxometalates and Metal-Organic Framework-Based Biomimetic Microhoneycomb Electromagnetic Wave-Absorbing Materials

Trinitarian designs in the morphology, components, and microstructure remain challenging for advanced electromagnetic wave absorption (EMWA) materials with light weight, strong absorption, and well-defined structure-function relationships. Herein, a series of X-doped MoS2/Cu9S5 with multilevel honeycomb structures (X-MoS2/Cu9S5 MHs, X = P, Si, Ge) were designed by space-confined growth and in situ sulfidation of a polyoxometalate-based metal-organic framework. X-MoS2/Cu9S5 MHs possess low density, high surface area, and abundant cation-cuprum and anion-sulfur double vacancies (VCu and VS) simultaneously that are unmatched by conventional EMWA materials. Also, the systematic investigation of the doping effect of various polyoxometalate heteroatoms on VCu and VS in the microhoneycomb has been conducted. Experimental results and density functional theory calculations reveal that the excellent EMWA performance (-56.21 dB) results from the synergistic effect of morphology design, component optimization, and vacancy regulation. This study not only provides an important opportunity to understand a morphology-component-microstructure strategy in electromagnetic wave absorption but also builds a noteworthy bridge between bioinspired engineering and microscale absorbers.

Photosynthetic System Based on a Polyoxometalate-Based Dehydrated Metal-Organic Framework for Nitrogen Fixation

In nature, biological nitrogen fixation is accomplished through the π-back-bonding mechanism of nitrogenase, which poses significant challenges for mimic artificial systems, thanks to the activation barrier associated with the N≡N bond. Consequently, this motivates us to develop efficient and reusable photocatalysts for artificial nitrogen fixation under mild conditions. We employ a charge-assisted self-assembly process toward encapsulating one polyoxometalate (POM) within a dehydrated Zr-based metal-organic framework (d-UiO-66) exhibiting nitrogen photofixation activities, thereby constructing an enzyme-mimicking photocatalyst. The dehydration of d-UiO-66 is favorable for facilitating nitrogen chemisorption and activation via the unpaired d-orbital electron at the [Zr6O6] cluster. The incorporation of POM guests enhanced the charge separation in the composites, thereby facilitating the transfer of photoexcited electrons into the π* antibonding orbital of chemisorbed N2 for efficient nitrogen fixation. Simultaneously, the catalytic efficiency of SiW9Fe3@d-UiO-66 is enhanced by 9.0 times compared to that of d-UiO-66. Moreover, SiW9Fe3@d-UiO-66 exhibits an apparent quantum efficiency (AQE) of 0.254% at 550 nm. The tactics of "working-in-tandem" achieved by POMs and d-UiO-66 are extremely vital for enhancing artificial ammonia synthesis. This study presents a paradigm for the development of an efficient artificial catalyst for nitrogen photofixation, aiming to mimic the process of biological nitrogen fixation.