Ir-Doped CuPd Single-Crystalline Mesoporous Nanotetrahedrons for Ethylene Glycol Oxidation Electrocatalysis: Enhanced Selective Cleavage of C-C Bond.

The development of highly efficient electrocatalysts for complete oxidation of ethylene glycol (EG) in direct EG fuel cells is of decisive importance to hold higher energy efficiency. Despite some achievements, their progress, especially electrocatalytic selectivity to complete oxidated C1 products, is remarkably slower than expected. In this work, we developed a facile aqueous synthesis of Ir-doped CuPd single-crystalline mesoporous nanotetrahedrons (Ir-CuPd SMTs) as high-performance electrocatalyst for promoting oxidation cleavage of C-C bond in alkaline EG oxidation reaction (EGOR) electrocatalysis. The synthesis relied on precise reduction/co-nucleation and epitaxial growth of Ir, Cu and Pd precursors with cetyltrimethylammonium chloride as the mesopore-forming surfactant and extra Br- as the facet-selective agent under ambient conditions. The products featured concave nanotetrahedron morphology enclosed by well-defined (111) facets, single-crystalline and mesoporous structure radiated from the center, and uniform elemental composition without any phase separation. Ir-CuPd SMTs disclosed remarkably enhanced electrocatalytic activity and excellent stability as well as superior selectivity of C1 products for alkaline EGOR electrocatalysis. Detailed mechanism studies demonstrated that performance improvement came from structural and compositional synergies, which kinetically accelerated transports of electrons/reactants within active sites of penetrated mesopores and facilitated oxidation cleavage of high-energy-barrier C-C bond of EG for desired C1 products. More interestingly, Ir-CuPd SMTs performed well in coupled electrocatalysis of anode EGOR and cathode nitrate reduction, highlighting its high potential as bifunctional electrocatalyst in various applications.

Ultrathin Two-dimensional Layered Composite Carbosilicates from in situ Unzipped Carbon Nanotubes and Exfoliated Bulk Silica.

A key task in today's inorganic synthetic chemistry is to develop effective reactions, routes, and associated techniques aiming to create new functional materials with specifically desired multilevel structures and properties. Herein, we report an ultrathin two-dimensional layered composite of graphene ribbon and silicate via a simple and scalable one-pot reaction, which leads to the creation of a novel carbon-metal-silicate hybrid family: carbosilicate. The graphene ribbon is in situ formed by unzipping carbon nanotubes, while the ultrathin silicate is in situ obtained from bulk silica or commercial glass; transition metals (Fe or Ni) oxidized by water act as bridging agent, covalently bonding the two structures. The unprecedented structure combines the superior properties of the silicate and the nanocarbon, which triggers some specific novel properties. All processes during synthesis are complementary to each other. The associated synergistic chemistry could stimulate the discovery of a large class of more interesting, functionalized structures and materials.

Multi-Dimensional Molecular Self-Assembly Strategy for the Construction of Two-Dimensional Mesoporous Polydiaminopyridine and Carbon Materials.

Two-dimensional (2D) mesoporous polymers, combining the advantages of organic polymers, porous materials, and 2D materials, have received great attention in adsorption, catalysis, and energy storage. However, the synthesis of 2D mesoporous polymers is not only challenged by the complex 2D structure construction, but also by the low yield and difficulty in controlling the dynamics of the assembly during the generation of mesopores. Herein, a facile multi-dimensional molecular self-assembly strategy is reported for the preparation of 2D mesoporous polydiaminopyridines (MPDAPs), which features tunable pore sizes (17-35 nm) and abundant N content up to 18.0 at%. Benefitting from the abundant N sites, 2D nanostructure, and uniform-large mesopores, the 2D MPDAPs exhibit excellent catalytic performance for the Knoevenagel condensation reaction. After calcination under N2 atmosphere, the obtained 2D N-doped mesoporous carbon (NMCs) with large and uniform pore sizes, high surface areas, abundant N content (up to 23.1%), and a high ratio of basic N species (57.0% pyridinic N and 35.9% pyrrolic N) can show an excellent CO2 uptake density (11.7 µmol m-2 at 273 K), higher than previously reported porous materials.

Competition among Refined Hollow Structures in Schiff Base Polymer Derived Carbon Microspheres.

Synthetic polymer-derived hollow carbon spheres have great utilitarian value in many fields for which the synthesis of proper polymer precursors is a key process. The exploration of new suitable polymer precursors and the construction of refined hollow structures in emerging polymers are both of great significance for synthetic methodology and novel carbon materials. Here, for the first time Schiff base polymer (SBP) colloid spheres with refined hollow structures were synthesized by tandem gradient growth and confined polymerization processes. The Hill equation was employed as a mathematical model to explain the gradient growth of SBP spheres. The size-dependent inner structure of SBP spheres can be adjusted from hollow to multichamber-surrounded hollow, and then to a multichamber structure. SBP-derived carbon spheres having similar surface area and chemical composition but different inner structures provide an effective way to investigate the relationship between inner structure and performance.

Ordered Mesoporous Intermetallic Ga-Pt Nanoparticles: Phase-Controlled Synthesis and Performance in Oxygen Reduction Electrocatalysis.

The intermetallic phase control is a promising strategy to optimize the physicochemical properties of ordered intermetallic compounds and engineer their performance in various (electro)catalytic reactions. However, the intermetallic phase-dependent catalytic performance is still rarely reported because of the difficulty in synthesizing ordered intermetallics with precisely controlled phase structures at atomic level, especially having ordered mesoscopic structure/morphology. Here, we successfully reported a precise synthesis of two phase-pure mesoporous intermetallic gallium-platinum (meso-i-Ga-Pt) nanoparticles, including meso-i-Ga3 Pt5 with an orthorhombic space group and meso-i-Ga1 Pt1 with a non-symmorphic chiral cubic space group. The intermetallic phase control of ordered meso-i-Ga-Pt nanoparticles was realized by carefully tuning the induced Ga salts with different anions that optimized the free energies during the synthesis. The intermetallic phase-dependent catalytic performance of ordered meso-i-Ga-Pt was systematically evaluated for oxygen reduction reaction (ORR) electrocatalysis, with completely opposite catalytic performance in alkaline media. Interestingly, ordered meso-i-Ga1 Pt1 catalyst with chiral atomic arrangements disclosed unexpected high ORR activity and stability with 5.9 and 3.2 enhancement factors in mass activity compared to those of meso-i-Ga3 Pt5 and commercial Pt/C.

Efficient Selective Oxidation of Aromatic Alkanes by Double Cobalt Active Sites over Oxygen Vacancy-rich Mesoporous Co3 O4.

The development of efficient catalyst for selective oxidation of hydrocarbon to functional compounds remains a challenge. Herein, mesoporous Co3 O4 (mCo3 O4 -350) showed excellent catalytic activity for selective oxidation of aromatic-alkanes, especially for oxidation of ethylbenzene with a conversion of 42 % and selectivity of 90 % for acetophenone at 120 °C. Notably, mCo3 O4 presented a unique catalytic path of direct oxidation of aromatic-alkanes to aromatic ketones rather than the conventional stepwise oxidation to alcohols and then to ketones. Density functional theory calculations revealed that oxygen vacancies in mCo3 O4 activate around Co atoms, causing electronic state change from Co3+ (Oh) →Co2+ (Oh) . Co2+ (Oh) has great attraction to ethylbenzene, and weak interaction with O2 , which provide insufficient O2 for gradual oxidation of phenylethanol to acetophenone. Combined with high energy barrier for forming phenylethanol, the direct oxidation path from ethylbenzene to acetophenone is kinetically favorable on mCo3 O4 , sharply contrasted to non-selective oxidation of ethylbenzene on commercial Co3 O4 .

Interface and Charge Induced Molecular Self-Assembly Strategy for the Synthesis of Reduced Graphene Oxide Coated with Mesoporous Platinum Sheets.

The design of porous noble metal catalysts holds great promise in various electrocatalytic applications. However, it is still a challenge to improve the durability performance through constructing stable framework. Here, an interface and charge induced strategy is developed to synthesize large-sized continuous reduced graphene oxide@mesoporous platinum (denoted as rGO@mPt) sheets under kinetic control by molecular self-assembly design. Graphene oxide (GO) is a promising large-sized growth interface for platinum. Cationic surfactant dioctadecyldimethylammonium chloride bridges the negatively charged GO and platinum precursors, while creating interconnected mesopores. The successful synthesis of rGO@mPt sheets relies on proper kinetic control, which is achieved by controlling pH, temperature, and the complexation of bromide ions. rGO@mPt sheets present strong crystallinity with a pure face-centered cubic Pt phase. Worm-like mesostructures with an average pore size of 2.2 nm exist throughout the sheets. rGO@mPt sheets possess both stable framework and abundant active sites, which markedly improve the durability on methanol oxidation reaction while maintaining relatively good catalytic activity. Long-term stability test shows a slight loss of 1.2% activity after 250 cycles. Amperometric i-t curves reveal the mass current three times higher compared to commercial Pt/C at 3000 s.

Liquid Na/K Alloy Interfacial Synthesis of Functional Porous Carbon at Ambient Temperature.

The functional groups in porous carbon generally suffer a severe loss during the high-temperature carbonization. Instead, the low-temperature synthesis of carbon featuring porous structures and abundant functional groups is not only a solution that evades the pitfalls of pyrolysis but also is of significance for the development of synthetic methodology. Herein, a liquid metal interfacial engineering strategy is reported for the synthesis of porous carbon using CCl4 as the carbon precursor and sodium-potassium alloy (NaK) as the reducing agent, which is superior to traditional synthetic methods because it enables the engineering of a highly active liquid metal alloy microemulsion to directly generate porous carbon at ambient temperature. As synthesized porous carbon featured abundant carbon-chlorine bonds can be tandem-grafted with imidazole and 1,2-dibromoethane to achieve a CO2 cycloaddition catalyst, which exhibits excellent catalytic activity, in addition to exceptional stability.

A Modular Co-assembly Strategy for Ordered Mesoporous Perovskite Oxides with Abundant Surface Active Sites.

The ordered mesoporous perovskite oxides with well-defined mesostrcture and versatile metal sites are attractive, but their successful synthesis faces challenges of complicated assembly dynamics and pore collapse in crystalline calcination. Here, we propose an energy balance concept to reveal interplay relationship in assembly process and realize regulation of porous structure for mesoporous perovskite oxides. A series of ordered mesoporous perovskite oxides with unique porous structure were prepared by a modular co-assembly method. Mesoporous La2 Zr2 O7 shows 94 % conversion and 99 % selectivity for hydrogenation of 5-hydroxymethylfurfural (HMF) to 2,5-bis(hydroxymethyl)furan. Experiments reveal that rich Lewis acid sites, active Zr species, and favorable porous structure promote interaction between mesoporous La2 Zr2 O7 and HMF and reduce catalytic energy barrier. This work provides the insight into molecule co-assembly and developing multiple component ordered mesoporous materials.

A General Polymer-Oriented Acid-Mediated Self-Assembly Approach toward Crystalline Mesoporous Metal Sulfides.

Mesoporous metal sulfides (MMSs) with high surface areas and large pore volumes show great potential in many applications such as gas sensing, photodetection, and catalysis. However, the synthesis of MMSs is still challenging due to the uncontrollable fast precipitation between metal ions and S2- ions and the large volume contraction during the conversion of metal precursors to sulfides. Here, a general polymer-oriented acid-mediated self-assembly method to synthesize highly crystalline MMSs (e.g., ZnS, CdS, Ni3 S4 , CuS, and Znx Cd1- x S) by using polyethylenimine (PEI) as pore-forming agent is reported. In this method, acetic acid is designed as pH regulator and coordination agent to control the interactions between inorganic precursors and PEI, and adjust the reaction kinetics of metal ions and thioacetamide. This method endows a high degree of control over crystal structure and porous structure of MMSs. The surface areas and pore volumes of obtained MMSs are as high as 157 m2 g-1 and 1.149 cm3 g-1 , respectively. Benefiting from the abundant mesopores and homojunctions, mesoporous Zn0.56 Cd0.44 S shows a superior photocatalytic H2 generation rate of 14.3 mmol h-1 g-1 .

The Synthesis of Porous Na3 V2 (PO4 )3 for Sodium-Ion Storage.

Na3 V2 (PO4 )3 (NVP) has been regarded as a potential cathode material for sodium-ion batteries (SIBs) due to its excellent structural stability and rapid Na+ conductivity. However, its electrochemical performances are restricted by the large bulk structure and poor electronic conductivity. The construction of porous NVP materials is a powerful method to improve the electrochemical properties. This concept aims to provide an overview of recent progress of porous NVP materials for SIBs. Herein, the synthetic strategies and formation mechanisms of porous NVP materials as well as the relationship between the porous structures and electrochemical performances of NVP materials are reviewed. Furthermore, the challenges and prospects for the preparation of porous NVP materials in this field are outlined.

A Resol-Assisted Cationic Coordinative Co-assembly Approach to Mesoporous ABO3 Perovskite Oxides with Rich Oxygen Vacancy for Enhanced Hydrogenation of Furfural to Furfuryl Alcohol.

It is a challenge to obtain ABO3 perovskite oxides with favorable crystal phase and well-defined porous structure via existing approaches. Here, we design an effective and versatile strategy to construct mesoporous ABO3 perovskite oxides with functionalized nanocrystal frameworks and abundant oxygen vacancy sites via a resol-assisted cationic coordinative co-assembly approach. The as-prepared oxygen vacancy-rich mesoporous LaMnO3 as heterogeneous catalyst exhibits remarkable catalytic activity and stability for hydrogenation of furfural to furfuryl alcohol, including over 99 % conversion and 96 % selectivity. Combined with density functional theory calculation, the catalytic mechanism is elucidated, revealing that porous LaMnO3 nanocrystal framework is conducive to expose oxygen deficiency sites, which can facilitate the interaction between catalyst surface and catalytic substrate, leading to lower barrier in hydrogenation process.

A Solvent-Polarity-Induced Interface Self-Assembly Strategy towards Mesoporous Triazine-Based Carbon Materials.

Triazine-based materials with porous structure have recently received numerous attentions as a fascinating new class because of their superior potential for various applications. However, it is still a formidable challenge to obtain triazine-based materials with precise adjustable meso-scaled pore sizes and controllable pore structures by reported synthesis approaches. Herein, we develop a solvent polarity induced interface self-assembly strategy to construct mesoporous triazine-based carbon materials. In this method, we employ a mixed solvent system within a suitable range of polarity (0.223≤Lippert-Mataga parameter (Δf) ≤0.295) to induce valid self-assembly of skeleton precursor and surfactant. The as-prepared mesoporous triazine-based carbon materials possess uniform tunable pore sizes (8.2-14.0 nm), high surface areas and ultrahigh nitrogen content (up to 18 %). Owing to these intriguing advantages, the fabricated mesoporous triazine-based carbon materials as functionalized porous solid absorbents exhibit predominant CO2 adsorption performance and exceptional selectivity for the capture of CO2 over N2 .

Polymer Stabilized Droplet Templating towards Tunable Hierarchical Porosity in Single Crystalline Na3 V2 (PO4 )3 for Enhanced Sodium-Ion Storage.

Na3 V2 (PO4 )3 (NVP) is regarded as a potential cathode material for sodium-ion batteries, whereas, its performance is usually limited by inherent low electronic conductivity and dense bulk structure. Herein, we develop a facile polymer stabilized droplet template strategy to synthesize porous single crystal structured NVP. The pore structures (macrostructures, hierarchically meso/macrostructures, and mesostructures), pore sizes (5-2000 nm), and specific surface areas (26-158 m2 g-1 ) of the samples can be readily controlled by tuning the sizes of droplet templates. The resultant hierarchically meso/macropores NVP demonstrates superior sodium storage performances, because its porous single crystal structure owns solid-liquid Na+ transmission mode, shortens ion diffusion distance and provides large electrode-electrolyte contact area, greatly facilitating fast ionic transport. We believe the presented method will supply a novel avenue to prepare porous single crystal structured materials for anticipative applications.

Ligand-Assisted Coordinative Self-Assembly Method to Synthesize Mesoporous ZnxCd1-xS Nanospheres with Nano-Twin-Induced Phase Junction for Enhanced Photocatalytic H2 Evolution.

The designed synthesis of nanotwin architectures and thus-induced phase junctions expresses huge significance for semiconductor photocatalysts. However, current methods of producing nanotwins mainly involve high-temperature thermal treatment and tedious reaction steps, generally resulting in large bulk structure with ill-defined morphology and low specific surface area. Here, we propose a mild ligand-assisted coordinative self-assembly method to synthesize uniform mesoporous ZnxCd1-xS nanospheres with ultrahigh surface areas (148-312 m2 g-1) and controllable diameter (90-370 nm). Moreover, the sample possesses abundant phase junctions induced by nanotwins containing both hexagonal and cubic segments. With the synergy of the twin-induced phase junctions and high surface area, the as-prepared mesoporous Zn0.82Cd0.18S nanospheres exhibit a remarkable photocatalytic H2 evolution rate of 13.46 mmol h-1 g-1 with free noble metal. The mechanism of photocarrier dynamics was studied by transient photovoltage spectroscopy, manifesting that the photocarrier lifetime of Zn0.82Cd0.18S is largely prolonged and therefore improves the charge separation efficiency and photocatalytic activity.

Mesoporous anion-cation-codoped Co9S8 nanorings for enhanced electrocatalytic oxygen evolution reactions.

Recently, the design and synthesis of Co9S8 micro/nanostructures have attracted attention as electrochemical energy storage and conversion devices due to their low cost and environmental friendliness. Herein, Co9S8 nanorings were synthesized via a one-step solvothermal method with the incorporation of Fe ions, subsequently, properly selenized to boost their electrocatalytic performance. The morphology and structure of the series of cation and anion regulated Co9S8 nanorings were characterized, the electrochemical oxygen evolution reaction (OER) properties were assessed. It is worth noting that the as-prepared catalysts, especially the innovative Fe and Se ions double doped Co9S8 nanorings, denoted as Se/Fe-Co9S8-0.14, exhibited good electrocatalytic OER performance with low overpotential (298 mV) and high durability under alkaline conditions. This work provides a new perspective to develop non-noble metal Co9S8-based OER electrocatalysts with a superior electrocatalytic performance.

Holey Lamellar High-Entropy Oxide as an Ultra-High-Activity Heterogeneous Catalyst for Solvent-free Aerobic Oxidation of Benzyl Alcohol.

The development of noble-metal-free heterogeneous catalysts is promising for selective oxidation of aromatic alcohols; however, the relatively low conversion of non-noble metal catalysts under solvent-free atmospheric conditions hinders their industrial application. Now, a holey lamellar high entropy oxide (HEO) Co0.2 Ni0.2 Cu0.2 Mg0.2 Zn0.2 O material with mesoporous structure is prepared by an anchoring and merging process. The HEO has ultra-high catalytic activity for the solvent-free aerobic oxidation of benzyl alcohol. Up to 98 % conversion can be achieved in only 2 h, to our knowledge, the highest conversion of benzyl alcohol by oxidation to date. By regulating the catalytic reaction parameters, benzoic acid or benzaldehyde can be selectively optimized as the main product. Analytical characterizations and calculations provide a deeper insight into the catalysis mechanism, revealing abundant oxygen vacancies and holey lamellar framework contribute to the ultra-high catalytic activity.

Solvent-Free Self-Assembly for Scalable Preparation of Highly Crystalline Mesoporous Metal Oxides.

Mesoporous metal oxides (MMOs) have been demonstrated great potential in various applications. Up to now, the direct synthesis of MMOs is still limited to the solvent induced inorganic-organic self-assembly process. Here, we develop a facile, general, and high throughput solvent-free self-assembly strategy to synthesize a series of MMOs including single-component MMOs and multi-component MMOs (e.g., doped MMOs, composite MMOs, and polymetallic oxide) with high crystallinity and remarkable porous properties by grinding and heating raw materials. Compared with the traditional solution self-assembly process, the avoidance of solvents in this method not only greatly increases the yield of target products and synthesis efficiency, but also reduces the environmental pollution and the consumption of cost and energy. We believe the presented approach will pave a new avenue for scalable production of advanced mesoporous materials for various applications.

Dendritic Mesoporous Silica Nanoparticle Adjuvants Modified with Binuclear Aluminum Complex: Coordination Chemistry Dictates Adjuvanticity.

Aluminum-containing adjuvants used in vaccine formulations suffer from low cellular immunity, severe aggregation, and accumulation in the brain. Conventional aluminosilicates widely used in the chemical industry focus mainly on acidic sites for catalytic applications, but they are rarely used as adjuvants. Reported here is an innovative "ligand-assisted steric hindrance" strategy to create a high density of six-coordinate VI Al-OH groups with basicity on dendritic mesoporous silica nanoparticles as new nanoadjuvants. Compared to four-coordinate IV Al-modified counterparts, VI Al-OH-rich aluminosilicate nanoadjuvants enhance cellular delivery of antigens and provoke stronger cellular immunity. Moreover, the aluminum accumulation in the brain is more reduced than that with a commercial adjuvant. These results show that coordination chemistry can be used to control the adjuvanticity, providing new understanding in the development of next-generation vaccine adjuvants.

Effects of water on the stochastic motions of propane confined in MCM-41-S pores.

Hydrocarbons confined in porous media find applications in a wide variety of industries and therefore their diffusive behavior is widely studied. Most of the porous media found in natural environments are laden with water, which might affect the confined hydrocarbons. To quantify the effect of hydration, we report here a combined quasielastic neutron scattering (QENS) and molecular dynamics (MD) simulation study on the dynamics of propane confined in the 1.5 nm-wide micropores of MCM-41-S in the presence of water at 230 and 250 K. To eliminate the strong incoherent signal from water and emphasize the propane signal we have used heavy water (D2O). QENS data show two dynamically different populations of propane in MCM-41-S and suggest that the presence of water hinders the diffusion of propane. Weak elastic contributions to the QENS spectra suggest that only long-range translational motion of propane molecules contributes to the quasielastic broadening. MD simulations carried out using a model cylindrical silica pore of 1.6 nm diameter filled with water and propane agree with the experimental finding of water hindering the diffusion of propane. Further, the simulation results suggest that the slowing down of propane motions is a function of the water content within the pore and is stronger at higher water contents. At high water content, the structure and the dynamics, both translational and rotational, of propane are severely impacted. Simulation data suggest that the rotational motion of the propane molecule occurs on time scales much faster than those accessible with the QENS instrument used, and thus explain the weak elastic contribution to the QENS spectra measured in the experiments. This study shows the effects of hydration on the structure and dynamics of volatiles in porous media, which are of interest for fundamental understanding and applied studies of confined fluids.