Yi-nan Wu

Metal–Organic Frameworks with a Three-Dimensional Ordered Macroporous Structure: Dynamic Photonic Materials†

Tuning MOFs: When a metal-organic framework (MOF) with an ordered three-dimensional macroporous structure is integrated into a film, the resulting materials have an additional optical element, which can be used as a general and effective signal transducer. This, in combination with the hierarchical pore structure, makes these films interesting dynamic photonic materials with potential applications in sensors.

Magnetic Metal–Organic Frameworks: γ‐Fe2O3@MOFs via Confined In Situ Pyrolysis Method for Drug Delivery

A general one-step in situ pyrolysis route for the construction of metal-organic frameworks encapsulating superparamagnetic γ-Fe2O3NPs dispersed in the confined cavities of MOFs homogeneously is described. The integration of γ-Fe2O3 NPs or clusters into MOFs can endow these porous materials with superparamagnetic element. By the combination of the thermal stability of MOFs and pyrolysis of metal triacetylacetonate complex at matched conditions, the porous structure of MOFs are well maintained while the size-induced superparamagnetic property of nano γ-Fe2O3 is obtained. As a proof of concept, both the γ- Fe2O3@ZIF-8 and γ-Fe2O3@MIL-53(Al) were successfully prepared, and the latter was chosen to demonstrate its potential drug delivery as a magnetic MOF.

The removal of bisphenol A from aqueous solutions by MIL-53(Al) and mesostructured MIL-53(Al).

In this work, metal-organic framework MIL-53(Al){Al(OH)[O2C-C6H4-CO2]} and MIL-53(Al)-F127{Al(OH)[O2C-C6H4-CO2]} were synthesized and used as sorbents to remove bisphenol A (BPA) from aqueous system. The sorption kinetics data of BPA were found to be in agreement with the pseudo-second-order model. The equilibrium sorption amounts of BPA on MIL-53(Al) and MIL-53(Al)-F127 reached 329.2±16.5 and 472.7±23.6 mg g(-1), respectively, far more than that of commercial activated carbons (ranging from 129.6 to 263.1 mg g(-1)). Both MIL-53(Al) and MIL-53(Al)-F127 could remove BPA fast from aqueous solutions, and the required contact time to reach equilibrium was approximately 90 min for MIL-53(Al) and 30 min for MIL-53(Al)-F127, respectively. The optimum pH levels for the removal of BPA using MIL-53 (Al) and MIL-53(Al)-F127 were 4 and 6 separately. The optimum temperature for the sorption behavior of BPA on the two sorbents was 20 °C. The results performed show that the resulting products, as one kind of MOFs, can be regarded as a new class of sorbents for water treatment and could find great applications in the fields of environmental water pollution control and resources reuse.

Electrospun fibrous mats as skeletons to produce free-standing MOF membranes

Nanofibrous mats produced by electrospinning are ideal porous substrates for developing chemical systems due to their high specific surface area, large porosity, and enormous structural and chemical tunability. In this work, we report the fabrication of free-standing MOF membranes using electrospun nanofibrous mats as skeletons, and demonstrate the great potential of such nonwoven fiber mats as a new type of porous support in MOF research field. Direct deposition and seeded secondary growth approaches could be used to produce MOF materials within different nanofibrous skeletons, indicating that the developed method of generating MOF membranes has a remarkable flexibility. The characterizations performed show that the resulting products combine the unique properties of both electrospun nanofibers and MOFs, and can be regarded as a new class of hierarchically nanostructured functional materials.

Poly(ionic liquid) brush coated electrospun membrane: a useful platform for the development of functionalized membrane systems

In this work, poly(ionic liquid) brushes were successfully grafted to the electrospun SiO2 nanofiber surface with atom transfer radical polymerization (ATRP) technology. By adjusting the density of initiator sites on the nanofiber surface, the core–shell structure was fabricated, which could clearly be “seen” with transmission electron microscopy (TEM). Combining the unique properties of an ionic liquid and electrospun nanofibrous mat, this hierarchically structured membrane provides a useful platform for developing functionalized membrane systems. With counteranion exchange of the attached poly(ionic liquid) brushes, the properties and functionality of the prepared membrane can be easily adjusted or integrated on need. As a demonstration, such a membrane served as an nion-directed molecular gating system. With counteranion exchange, the surface properties of the membrane were reversibly altered between hydrophilic to hydrophobic, which makes pores withdraw or expel solvent molecules (H2O), thus controlling the transport of probe molecules through the membrane. As a further example, electroactive polyoxometalate (POM) units were incorporated into the membrane through simple counteranion exchange, and a functionalized membrane with electroactivity was also achieved. In this work, various characterization techniques including infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and electrochemical measurements were used to characterize the related membrane systems.

The Metal-Organic Framework MIL-53(Al) Constructed from Multiple Metal Sources: Alumina, Aluminum Hydroxide, and Boehmite

Three aluminum compounds, namely alumina, aluminum hydroxide, and boehmite, are probed as the metal sources for the hydrothermal synthesis of a typical metal-organic framework MIL-53(Al). The process exhibits enhanced synthetic efficiency without the generation of strongly acidic byproducts. The time-course monitoring of conversion from different aluminum sources into MIL-53(Al) is achieved by multiple characterization that reveals a similar but differentiated crystallinity, porosity, and morphology relative to typical MIL-53(Al) prepared from water-soluble aluminum salts. Moreover, the prepared MIL-53(Al) constructed with the three insoluble aluminum sources exhibit an improved thermal stability of up to nearly 600 °C and enhanced yields. Alumina and boehmite are more preferable than aluminum hydroxide in terms of product porosity, yield, and reaction time. The adsorption performances of a typical environmental endocrine disruptor, dimethyl phthalate, on the prepared MIL-53(Al) samples are also investigated. The improved structural stability of MIL-53(Al) prepared from these alternative aluminum sources enables double-enhanced adsorption performance (up to 206 mg g(-1)) relative to the conventionally obtained MIL-53(Al).

Electrospun fibrous mats as a skeleton for fabricating hierarchically structured materials as sorbents for Cu2

Based on the combination of the electrospinning and evaporation-induced self-assembly mesopore-forming technique, a facile strategy is developed to fabricate self-standing thiol-functionalized membranes with hierarchical structures (Macro-Mesopores and binding sites). This membrane is prepared using electrospun polystyrene (PS) fibers as the skeleton and non-ionic surfactant F127 as the structure-directing agent with co-condensation of tetraethyl orthosilicate (TEOS) and 3-mercaptopropyltrimethoxysilane (MPTMS). The prepared membranes were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), nitrogen sorption, mercury intrusion porosimetry, and Fourier transform infrared (FT-IR) spectra. The macropore constructed by the electrospun PS membrane ranged from 1 to 10 μm, while the highly ordered mesopore formed by F127 was around 5 nm and heavy metals binding cites of thiol groups were also presented, respectively. Using Cu2+ ions as the model bivalent cation, an excellent removal capacity of the prepared membrane was confirmed by the static sorption and dynamic filtration experiments with a high flux up to 1.30 × 104 L h−1 m−2bar−1. We find that regeneration of the membranes and the metal ion recovery can be facially realized by the treatment using acid solution. These results demonstrate that the developed strategy has significant potential for the design and fabrication of high-performance membranes with hierarchical structures and could find impactful application in the field of industrial catalysis, separation, and environmental pollution control and resources reuse.

General Deposition of Metal–Organic Frameworks on Highly Adaptive Organic–Inorganic Hybrid Electrospun Fibrous Substrates

Electrospun nanofibrous mats are ideal substrates for metal-organic frameworks (MOFs) crystal deposition because of their specific structural parameters and chemical tenability. In this work, we utilized organic-inorganic hybrid electrospun fibrous mats as support material to study the deposition of various MOF particles. HKUST-1 and MIL-53(Al) were produced through solvothermal method, while ZIF-8 and MIL-88B(Fe) were prepared using microwave-induced heating method. The synthesis procedure for both methods were simple and effective because the hybrid nanofibrous mats showed considerable affinity to MOF particles and could be used without additional modifications. The obtained MOF composites exhibited effective incorporation between MOF particles and the porous substrates. MIL-53(Al) composite was applied as fibrous sorbent and showed enhanced adsorption capacity and removal rate, as well as easier operation, compared with thepowdered sample. Moreover, MIL-53(Al) composite was easier to be regenerated compared with powder form.

Direct synthesis of novel vanadium oxide embedded porous carbon nanofiber decorated with iron nanoparticles as a low-cost and highly efficient visible-light-driven photocatalyst.

Template-free porous carbon nanofibers embedded by vanadium oxide and decorated with iron nanoparticles (Fe@V-CNF) were prepared in a time and cost-saving manner by combining electrospinning and heat treatment processes. Cost-saving ammonium metavanadate was used as a semiconductor precursor of vanadium oxide (VOx) as well as porogen. The generated pores in the carbon nanofiber (CNFs) matrix formed pathways between the embedded VOx and the surface of CNFs and Fe NPs, thus, facilitate photo-generated electron transfer. The characterization results revealed that Fe@V-CNF comprised graphitic fibers with well-dispersed distribution of nanosized Fe NPs (~7 nm) along the surface of CNF. Thereby, it enhanced the visible-light harvesting. The prepared Fe@V-CNF had remarkable light absorption in the visible region. It demonstrated much higher photocatalytic efficiency of photodegradation of organic dyes compared with the pure CNF and vanadium oxide embedded CNF (V-CNF). Notably, Fe@V-CNF achieved 99.9% dye degradation within 15-20 min. And, it could be conveniently recycled due to its one-dimensional nanostructural property.

Adsorption of Rhodamine B dye by biomimetic mesoporous SiO2 nanosheets

Efficient treatment of solutions and solid wastes containing Rhodamine B (RB), a common dye with potential carcinogenicity and sometimes used illegally in food industry, is of great importance because inappropriate treatment may lead to serious human and environmental risks. A novel nanomaterial, the mesoporous silica nanosheets prepared via electrospinning and calcination are applied to the adsorption of RB from aqueous solutions in this work. This sheet-like material is superior to classic powder adsorbents in recoverability, while good availability and stability favor its practical application. The effects of key parameters such as system pH, stirring rate, initial concentration, and contact time are studied. The adsorption isotherm type and the kinetic characteristic are analyzed. The results show that the mesoporous SiO2 nanosheets are efficient in removing RB from aqueous phase, presenting great potential to become a practical dye adsorbent. Regeneration experiments show that this novel adsorbent can be activated by ethanol extraction process. This study provides the academic field with a successful application case of nanostructured materials, which can be applied to a wider range of dyes similar to RB in physicochemical properties, showing prosperous value in advanced environmental purification.