Development of Amino-Functionalized Silica by Co-condensation and Alkylation for Direct Air Capture.

CO chemisorption using amine-based sorbents is one of the most effective techniques for carbon capture and storage. Solid CO sorbents with amines immobilized on their surface have been attracting attention due to the easy collection of sorbents and reusability. In this study, we developed a solid CO adsorbent by co-condensation of a silanizing reagent having a chloroalkyl group and tetraethyl ethoxysilane, followed by alkylation of the chloroalkyl group with diamine.

QXAFS study of CO and H adsorption on Pt in [PtAu(PPh)]-H[PMoO] solid.

The adsorption behaviors of H and CO molecules in crown-motif [PtAu(PPh)]-H[PMoO] (PtAu8-PMo12) solids were investigated by quick-scan X-ray absorption fine structure (QXAFS) measurements with a time resolution of 0.1 s. The electronic state of Pt in PtAu8-PMo12 was drastically changed by the adsorption of H and CO molecules because of the formation of Pt-H/Pt-CO interactions.

Low-Temperature Desorption of CO from Carbamic Acid for CO Condensation by Direct Air Capture.

The high temperature requirement for the desorption of absorbed CO is one of the issues for the widespread use of direct air capture (DAC), which is a promising technology to reduce atmospheric CO concentration. This work realized a liquid diamine absorbent-solid carbamic acid (CA) phase-change DAC system with CO desorption at a low temperature by using a MeOH solvent. The CA of isophoronediamine [3-(aminomethyl)-3,5,5-trimethylcyclohexylamine, CA-IPDA] readily desorbed CO in MeOH at 50 °C, while IPDA showed the capacity to absorb low-concentration CO from air with an IPDA/CO ratio of 1:1.

Electronic state modulation of Ag nanoclusters within a ring-shaped polyoxometalate.

Atomically precise Ag nanoclusters display distinctive properties that are dictated by their structures and electronic states. However, manipulating the electronic states of Ag nanoclusters is challenging owing to their inherent instability and susceptibility to undesired structural changes, decomposition, and aggregation. Recently, we reported the synthesis of a body-centered cubic {Ag} nanocluster encapsulated within a ring-shaped polyoxometalate (POM) [PWO] by reacting 16 Ag-containing [PWO] with Ag using ,-dimethylformamide (DMF) as a mild reducing agent.

Synthesis of a Gold-Silver Alloy Nanocluster within a Ring-Shaped Polyoxometalate and Its Photocatalytic Property.

Alloying is an effective method for modulating metal nanoclusters to enrich their structural diversity and physicochemical properties. Recent investigations have demonstrated that polyoxometalates (POMs) can act as effective multidentate ligands for silver (Ag) nanoclusters to endow them with synergistic properties, reactivity, catalytic properties, and stability. However, the application of POMs as ligands has been confined predominantly to monometallic nanoclusters.

Small Copper Nanoclusters Synthesized through Solid-State Reduction inside a Ring-Shaped Polyoxometalate Nanoreactor.

Cu nanoclusters exhibit distinctive physicochemical properties and hold significant potential for multifaceted applications. Although Cu nanoclusters are synthesized by reacting Cu ions and reducing agents by covering their surfaces using organic protecting ligands or supporting them inside porous materials, the synthesis of surface-exposed Cu nanoclusters with a controlled number of Cu atoms remains challenging. This study presents a solid-state reduction method for the synthesis of Cu nanoclusters employing a ring-shaped polyoxometalate (POM) as a structurally defined and rigid molecular nanoreactor.

Ultra-stable and highly reactive colloidal gold nanoparticle catalysts protected using multi-dentate metal oxide nanoclusters.

Owing to their remarkable properties, gold nanoparticles are applied in diverse fields, including catalysis, electronics, energy conversion and sensors. However, for catalytic applications of colloidal gold nanoparticles, the trade-off between their reactivity and stability is a significant concern. Here we report a universal approach for preparing stable and reactive colloidal small (~3 nm) gold nanoparticles by using multi-dentate polyoxometalates as protecting agents in non-polar solvents.

Counteranion-induced structural isomerization of phosphine-protected PdAu and PtAu clusters.

Controlling the geometric structures of metal clusters through structural isomerization allows for tuning of their electronic state. In this study, we successfully synthesized butterfly-motif [PdAu(PPh)] (PdAu8-B, B means butterfly-motif) and [PtAu(PPh)] (PtAu8-B) by the structural isomerization from crown-motif [PdAu(PPh)] (PdAu8-C, C means crown-motif) and [PtAu(PPh)] (PtAu8-C), induced by association with anionic polyoxometalate, [MoO] (Mo6) respectively, whereas their structural isomerization was suppressed by the use of [NO] and [PMoO] as counter anions. DR-UV-vis-NIR and XAFS analyses and density functional theory calculations revealed that the synthesized [PdAu(PPh)][MoO] (PdAu8-Mo6) and [PtAu(PPh)][MoO] (PtAu8-Mo6) had PdAu8-B and PtAu8-B respectively because PdAu8-Mo6 and PtAu8-Mo6 had bands in optical absorption at the longer wavelength region and different structural parameters characteristic of the butterfly-motif structure obtained by XAFS analysis.

Size-Controlled Synthesis of Luminescent Few-Atom Silver Clusters via Electron Transfer in Isostructural Redox-Active Porous Ionic Crystals.

Ag clusters with a controlled number of atoms have received significant interest because they show size-dependent catalytic, optical, electronic, or magnetic properties. However, the synthesis of size-controlled, ligand-free, and air-stable Ag clusters with high yields has not been well-established. Herein, it is shown that isostructural porous ionic crystals (PICs) with redox-active polyoxometalates (POMs) can be used to synthesize Ag clusters via electron transfer from POMs to Ag .

Improved activity for the oxygen evolution reaction using a tiara-like thiolate-protected nickel nanocluster.

Practical electrochemical water splitting and carbon-dioxide reduction are desirable for a sustainable energy society. In particular, facilitating the oxygen evolution reaction (OER, the reaction at the anode) will increase the efficiency of these reactions. Nickel (Ni) compounds are excellent OER catalysts under basic conditions, and atomically precise Ni clusters have been actively studied to understand their complex reaction mechanisms.

Dual functional catalysis of [NbO]-modified Au/AlO.

A catalyst prepared by modifying the surface of Au nanoparticles (NPs) on AlO with [NbO] clusters had specific base and reduction abilities, and the reduction of -nitrophenol to -aminophenol using H as a reductant proceeded efficiently with the dual functional catalyst. At the interface between Au NPs and basic [NbO], heterolytically cleaved hydrogen species are generated, which can efficiently react with nitrophenolate ions generated by base catalysis. Moreover, this surface modification strategy was applicable to the reduction of other nitro compounds.

Control over Ligand-Exchange Positions of Thiolate-Protected Gold Nanoclusters Using Steric Repulsion of Protecting Ligands.

Organic ligands on gold nanoclusters play important roles in regulating the structures of gold cores. However, the impact of the number and positions of the protecting ligands on gold-core structures remains unclear. We isolated thiolate-protected Au cluster anions, and ( = 2-phenylethanethiolate), obtained by ligand exchange of with one or two porphyrinthiolate () ligands as mixtures of regioisomers.

Variable control of the electronic states of a silver nanocluster protonation/deprotonation of polyoxometalate ligands.

The properties of metal nanoclusters depend on both their structures and electronic states. However, in contrast to the significant advances achieved in the synthesis of structurally well-defined metal nanoclusters, systematic control of their electronic states is still challenging. In particular, stimuli-responsive and reversible control of the electronic states of metal nanoclusters is attractive from the viewpoint of their practical applications.

Supported Anionic Gold Nanoparticle Catalysts Modified Using Highly Negatively Charged Multivacant Polyoxometalates.

Although supported anionic gold nanoparticle catalysts have been theoretically investigated for their efficacy in activating O in aerobic oxidation reactions, limited studies have been reported due to the difficulty of designing these catalysts. Herein, we developed a feasible method for preparing supported anionic gold nanoparticle catalysts using multivacant lacunary polyoxometalates with high negative charges. We confirmed the strong and robust electronic interaction between gold nanoparticles and multivacant lacunary polyoxometalates, and the electronic states of the supported gold nanoparticle catalysts can be sequentially modulated.

Simple and high-yield preparation of carbon-black-supported ∼1 nm platinum nanoclusters and their oxygen reduction reactivity.

The improvement of oxygen reduction reaction (ORR) catalysts is essential before polymer electrolyte fuel cells can be used widely. To this end, we established a simple method for the size-selective synthesis of a series of ligand-protected platinum nanoclusters with ∼1 nm particle size (Pt NCs; = ∼35, ∼51, and ∼66) and narrow size distribution (±∼4 Pt atoms) under atmospheric conditions. Using this method, each ligand-protected ∼1 nm Pt NC was obtained in a relatively high yield (nearly 80% for Pt).

Creation of High-Performance Heterogeneous Photocatalysts by Controlling Ligand Desorption and Particle Size of Gold Nanocluster.

Recently, the creation of new heterogeneous catalysts using the unique electronic/geometric structures of small metal nanoclusters (NCs) has received considerable attention. However, to achieve this, it is extremely important to establish methods to remove the ligands from ligand-protected metal NCs while preventing the aggregation of metal NCs. In this study, the ligand-desorption process during calcination was followed for metal-oxide-supported 2-phenylethanethiolate-protected gold (Au) 25-atom metal NCs using five experimental techniques.

Imparting CO reduction selectivity to ZnGaO photocatalysts by crystallization from hetero nano assembly of amorphous-like metal hydroxides.

Imparting an enhanced CO reduction selectivity to ZnGaO photocatalysts has been demonstrated by controlled crystallization from interdispersed nanoparticles of zinc and gallium hydroxides. The hydroxide precursor in which Zn(ii) and Ga(iii) are homogeneously interdispersed was prepared through an epoxide-driven sol-gel reaction. ZnGaO obtained by a heat-treatment exhibits a higher surface basicity and an enhanced affinity for CO molecules than previously-reported standard ZnGaO.

Investigation of the electrochemical and photoelectrochemical properties of Ni-Al LDH photocatalysts.

Layered double hydroxide (LDH) photocatalysts, including Ni-Al LDH, are active for the photocatalytic conversion of CO2 in water under UV light irradiation. In this study, we found that a series of LDHs exhibited anodic photocurrent which is a characteristic feature corresponding to n-type materials. Also, we estimated the potentials of photogenerated electrons and holes for LDHs, which are responsible for the photocatalytic reactions, using electrochemical techniques.