Andrew J. Binder

Template-Free Synthesis of Hierarchical Porous Metal-Organic Frameworks

A template-free synthesis of a hierarchical microporous-mesoporous metal-organic framework (MOF) of zinc(II) 2,5-dihydroxy-1,4-benzenedicarboxylate (Zn-MOF-74) is reported. The surface morphology and porosity of the bimodal materials can be modified by etching the pore walls with various synthesis solvents for different reaction times. This template-free strategy enables the preparation of stable frameworks with mesopores exceeding 15 nm, which was previously unattained in the synthesis of MOFs by the ligand-extension method.

An efficient and reusable “hairy” particle acid catalyst for the synthesis of 5-hydroxymethylfurfural from dehydration of fructose in water

Poly(4-styrenesulfonic acid) brush-grafted silica particles, synthesized by surface-initiated atom transfer radical polymerization, were employed as a reusable acid catalyst for dehydration of fructose to 5-hydroxymethylfurfural (HMF) in water. The particles exhibited a high activity with the HMF yield of up to 31%, in contrast to 26% from the corresponding free homopolymer catalyst.

Hierarchically Superstructured Prussian Blue Analogues: Spontaneous Assembly Synthesis and Applications as Pseudocapacitive Materials

Hierarchically superstructured Prussian blue analogues (hexacyanoferrate, M=Ni(II) , Co(II) and Cu(II) ) are synthesized through a spontaneous assembly technique. In sharp contrast to macroporous-only Prussian blue analogues, the hierarchically superstructured porous Prussian blue materials are demonstrated to possess a high capacitance, which is similar to those of the conventional hybrid graphene/MnO2 nanostructured textiles. Because sodium or potassium ions are involved in energy storage processes, more environmentally neutral electrolytes can be utilized, making the superstructured porous Prussian blue analogues a great contender for applications as high-performance pseudocapacitors.

Macroporous monoliths for trace metal extraction from seawater

The viability of seawater-based uranium recovery depends on the uranium adsorption rate and capacity, since the concentration of uranium in the oceans is relatively low (3.3 μg L−1). An important consideration for a fast adsorption is to maximize the adsorption properties of adsorbents such as surface areas and pore structures, which can greatly improve the kinetics of uranium extraction and the adsorption capacity simultaneously. Following this consideration, macroporous monolith adsorbents were prepared from the copolymerization of acrylonitrile (AN) and N,N′-methylene-bis(acrylamide) (MBAAm) based on a cryogel method using both hydrophobic and hydrophilic monomers. The monolithic sorbents were tested with simulated seawater containing a high uranyl concentration (∼6 ppm) and the uranium adsorption results showed that the adsorption capacities are strongly influenced by the ratio of monomer to the crosslinker, i.e., the density of the amidoxime groups. The preliminary seawater testing indicates the high salinity content of seawater does not hinder the adsorption of uranium.

Three-Phase Catalytic System of H2O, Ionic Liquid, and VOPO4–SiO2 Solid Acid for Conversion of Fructose to 5-Hydroxymethylfurfural

Efficient transformation of biomass-derived feedstocks to chemicals and fuels remains a daunting challenge in utilizing biomass as alternatives to fossil resources. A three-phase catalytic system, consisting of an aqueous phase, a hydrophobic ionic-liquid phase, and a solid-acid catalyst phase of nanostructured vanadium phosphate and mesostructured cellular foam (VPO-MCF), is developed for efficient conversion of biomass-derived fructose to 5-hydroxymethylfurfural (HMF). HMF is a promising, versatile building block for production of value-added chemicals and transportation fuels. The essence of this three-phase system lies in enabling the isolation of the solid-acid catalyst from the aqueous phase and regulation of its local environment by using a hydrophobic ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][Tf2N]). This system significantly inhibits the side reactions of HMF with H2O and leads to 91 mol % selectivity to HMF at 89 % of fructose conversion. The unique three-phase catalytic system opens up an alternative avenue for making solid-acid catalyst systems with controlled and locally regulated microenvironment near catalytically active sites by using a hydrophobic ionic liquid.

In situ growth synthesis of heterostructured LnPO4–SiO2 (Ln = La, Ce, and Eu) mesoporous materials as supports for small gold particles used in catalytic CO oxidation

A general in situ growth method was successfully employed to prepare lanthanide phosphate–SiO2 mesostructured cellular foams (MCFs) (LnPO4–MCFs; Ln = La, Ce, and Eu; MCFs = SiO2). These heterostructured MCFs (LnPO4–MCFs) feature binary interpenetrating LnPO4 and silica frameworks, large surface areas, and uniform mesopore diameters. They were characterized by small-angle X-ray scattering, X-ray diffraction, nitrogen sorption, and transmission electron microscopy. The essence of this in situ growth synthesis lies in the controlled heterogeneous reaction of highly dispersed lanthanide oxides embedded in MCFs with phosphate ions in solution, leading to the formation of highly dispersed crystalline phosphate nanorods (nanocrystalline LnPO4) on the walls of MCFs. The resultant heterostructured LnPO4–MCFs were used as a novel support system for gold catalysts in CO oxidation at low temperatures. Gold precursor species can be readily introduced on LnPO4 nanophases of LnPO4–MCFs via a simple deposition–precipitation method. The resulting Au–LnPO4–MCF (2 wt% Au) catalysts exhibited high catalytic activities even below room temperatures. Because of the alteration of surface properties engineered by the in situ growth methodology and the strong interaction of metallic gold species with LnPO4, these catalysts are highly sinter-resistant. Although some cationic Au species are also present on the LnPO4–MCF surfaces, the metallic gold species are shown to be the key catalytic active sites for CO oxidation via in situ infrared spectroscopy.

Synthesis of metal–organic framework particles and thin films via nanoscopic metal oxide precursors

Metal–organic frameworks (MOFs) are a diverse family of hybrid inorganic–organic crystalline solids synthesized by assembling secondary building units (SBUs) and organic ligands into a periodic and porous framework. Microporous MOF materials, due to their high permeability and size selectivity, have attracted tremendous interest in gas storage and separation, large molecule adsorption, catalysis, and sensing. Despite the significant fabrication challenges, nanosized MOF particles can be fabricated to display enhanced gas storage and separation abilities in comparison to the parent MOF bulk counterparts under special synthesis conditions. So far, the majority of MOF nanocrystals have been derived from the controlled nucleation and growth of molecular precursors in homogeneous solutions. However, synthesis protocols based on nucleation and growth from dilute solution precursors are difficult to adapt to the synthesis of other nanoscopic materials, such as thin film and mixed-matrix membranes, which limits the practical applications of MOFs. This article discusses the current status of synthetic methods that have been utilized to fabricate MOF-based nanoscopic materials and ultrathin membranes from nanoscopic metal oxide precursors.

Heterostructured BaSO4–SiO2 mesoporous materials as new supports for gold nanoparticles in low-temperature CO oxidation

Nanosized BaSO4-based mesoporous hybrid materials have been developed and identified as new efficient inorganic salt-based support systems for ultrastable gold nanoparticles in low-temperature CO oxidation.

Deposition-Precipitation and Stabilization of a Silica-Supported Au Catalyst by Surface Modification with Carbon Nitride

A silica support is modified by carbon nitride in order to allow for the deposition–precipitation of Au, which is normally unfavorable. The resulting catalyst is highly stable even after the removal of the carbon nitride layer at high temperature and shows good catalytic activity for the oxidation of CO in air.Graphical Abstract