Metal-Organic Frameworks for Liquid Phase Applications

Classifying and Predicting the Thermal Expansion Properties of Metal-Organic Frameworks: A Data-Driven Approach

Metal-organic frameworks (MOFs) are versatile materials for a wide variety of potential applications. Tunable thermal expansion properties promote the application of MOFs in thermally sensitive composite materials; however, they are currently available only in a handful of structures. Herein, we report the first data set for thermal expansion properties of 33,131 diverse MOFs generated from molecular simulations and subsequently develop machine learning (ML) models to (1) classify different thermal expansion behaviors and (2) predict volumetric thermal expansion coefficients (αV). The random forest model trained on hybrid descriptors combining geometric, chemical, and topological features exhibits the best performance among different ML models. Based on feature importance analysis, linker chemistry and topological arrangement are revealed to have a dominant impact on thermal expansion. Furthermore, we identify common building blocks in MOFs with exceptional thermal expansion properties. This data-driven study is the first of its kind, not only constructing a useful data set to facilitate future studies on this important topic but also providing design guidelines for advancing new MOFs with desired thermal expansion properties.

Unveiling the MIL-53(Al) MOF: Tuning Photoluminescence and Structural Properties via Volatile Organic Compounds Interactions

MIL-53(Al) is a metal-organic framework (MOF) with unique properties, including structural flexibility, thermal stability, and luminescence. Its ability to adsorb volatile organic compounds (VOCs) and water vapor makes it a promising platform for sensing applications. This study investigated the adsorption mechanism of MIL-53(Al) with different VOCs, including ketones, alcohols, aromatics, and water molecules, focusing on structural transformations due to pore size variation and photoluminescence properties. The reported results assess MIL-53(Al) selectivity towards different VOCs and provide insights into their fundamental properties and potential applications in sensing.

Laser-Driven Rapid Synthesis of Metal-Organic Frameworks and Investigation of UV-NIR Optical Absorption, Luminescence, Photocatalytic Degradation, and Gas and Ion Adsorption Properties

In this study, we designed a platform based on a laser-driven approach for fast, efficient, and controllable MOF synthesis. The laser irradiation method was performed for the first time to synthesize Zn-based MOFs in record production time (approximately one hour) compared to all known MOF production methods with comparable morphology. In addition to well-known structural properties, we revealed that the obtained ZnMOFs have a novel optical response, including photoluminescence behavior in the visible range with nanosecond relaxation time, which is also supported by first-principles calculations. Additionally, photocatalytic degradation of methylene blue with ZnMOF was achieved, degrading the 10 ppm methylene blue (MB) solution 83% during 1 min of irradiation time. The application of laser technology can inspire the development of a novel and competent platform for a fast MOF fabrication process and extend the possible applications of MOFs to miniaturized optoelectronic and photonic devices.

Biomimetic and bioorthogonal nanozymes for biomedical applications

Nanozymes mimic the function of enzymes, which drive essential intracellular chemical reactions that govern biological processes. They efficiently generate or degrade specific biomolecules that can initiate or inhibit biological processes, regulating cellular behaviors. Two approaches for utilizing nanozymes in intracellular chemistry have been reported. Biomimetic catalysis replicates the identical reactions of natural enzymes, and bioorthogonal catalysis enables chemistries inaccessible in cells. Various nanozymes based on nanomaterials and catalytic metals are employed to attain intended specific catalysis in cells either to mimic the enzymatic mechanism and kinetics or expand inaccessible chemistries. Each nanozyme approach has its own intrinsic advantages and limitations, making them complementary for diverse and specific applications. This review summarizes the strategies for intracellular catalysis and applications of biomimetic and bioorthogonal nanozymes, including a discussion of their limitations and future research directions.

Charge transfer in metal-organic frameworks

Metal-organic frameworks (MOFs, also known as porous coordination polymers or PCPs) are a novel class of crystalline porous material. The tailorable porous structure, in terms of size, geometry and function, has attracted the attention of researchers across all disciplines of materials science. One of the many exciting aspects of MOFs is that through directional and reversible coordination bonding, organic linkers (chromophores with metal-coordinating functional groups) and metal ions (and clusters) can be spatially organized in a preconceived geometry. The well-defined spatial geometry of the metals and linkers is very advantageous for optoelectronic functions (solar cells, light-emitting diodes, photocatalysts) of the materials. This feature article evaluates the scope of charge transfer (CT) interactions in MOFs, involving the organic linkers and metal ion or cluster components. Irrespective of the type (size, shape, electronic property) of organic chromophores involved, MOFs provide an insightful path to design and make the CT process efficient. The selected examples of MOFs with CT characteristics do not only illustrate the design principles but render a pathway towards understanding the complex photophysical processes and implementing those for future optoelectronic and catalytic applications.

Separation of Aromatic Hydrocarbons in Porous Materials

Industrial-scale thermal separation processes have contributed greatly to the rise in carbon dioxide emissions. Porous materials, such as metal-organic frameworks (MOFs), can potentially reduce these emissions by achieving nonthermal chemical separations through the physical adsorption of targeted species with high selectivity. Here, we report the synthesis of the channel-based MOFs NU-2000 and NU-2001, which are constructed from three-dimensional (3D) linkers, to separate the industrially relevant xylene isomers under ambient conditions by leveraging sub-Ångstrom differences in the sizes of each isomer. While the rotation of two-dimensional (2D) linkers in MOFs often affords changes in pore apertures and pore sizes that are substantial enough to hinder separation efficiency, increasing the linker dimensionality from 2D to three-dimensional (3D) enables precise control of the MOF pore size and aperture regardless of the linker orientation, establishing this design principle as a broadly applicable strategy.

Heterogeneous Dendrimer-Based Catalysts

The present review compiles the advances in the dendritic catalysis within the last two decades, in particular concerning heterogeneous dendrimer-based catalysts and their and application in various processes, such as hydrogenation, oxidation, cross-coupling reactions, etc. There are considered three main approaches to the synthesis of immobilized heterogeneous dendrimer-based catalysts: (1) impregnation/adsorption on silica or carbon carriers; (2) dendrimer covalent grafting to various supports (silica, polystyrene, carbon nanotubes, porous aromatic frameworks, etc.), which may be performed in a divergent (as a gradual dendron growth on the support) or convergent way (as a grafting of whole dendrimer to the support); and (3) dendrimer cross-linking, using transition metal ions (resulting in coordination polymer networks) or bifunctional organic linkers, whose size, polarity, and rigidity define the properties of the resulted material. Additionally, magnetically separable dendritic catalysts, which can be synthesized using the three above-mentioned approaches, are also considered. Dendritic catalysts, synthesized in such ways, can be stored as powders and be easily separated from the reaction medium by filtration/centrifugation as traditional heterogeneous catalysts, maintaining efficiency as for homogeneous dendritic catalysts.

A Materials Science Perspective of Midstream Challenges in the Utilization of Heavy Crude Oil

An increasing global population and a sharply upward trajectory of per capita energy consumption continue to drive the demand for fossil fuels, which remain integral to energy grids and the global transportation infrastructure. The oil and gas industry is increasingly reliant on unconventional deposits such as heavy crude oil and bitumen for reasons of accessibility, scale, and geopolitics. Unconventional deposits such as the Canadian Oil Sands in Northern Alberta contain more than one-third of the world's viscous oil reserves and are vital linchpins to meet the energy needs of rapidly industrializing populations. Heavy oil is typically recovered from subsurface deposits using thermal recovery approaches such as steam-assisted gravity drainage (SAGD). In this perspective article, we discuss several aspects of materials science challenges in the utilization of heavy crude oil with an emphasis on the needs of the Canadian Oil Sands. In particular, we discuss surface modification and materials' design approaches essential to operations under extreme environments of high temperatures and pressures and the presence of corrosive species. The demanding conditions for materials and surfaces are directly traceable to the high viscosity, low surface tension, and substantial sulfur content of heavy crude oil, which necessitates extensive energy-intensive thermal processes, warrants dilution/emulsification to ease the flow of rheologically challenging fluids, and engenders the need to protect corrodible components. Geopolitical reasons have further led to a considerable geographic separation between extraction sites and advanced refineries capable of processing heavy oils to a diverse slate of products, thus necessitating a massive midstream infrastructure for transportation of these rheologically challenging fluids. Innovations in fluid handling, bitumen processing, and midstream transportation are critical to the economic viability of heavy oil. Here, we discuss foundational principles, recent technological advancements, and unmet needs emphasizing candidate solutions for thermal insulation, membrane-assisted separations, corrosion protection, and midstream bitumen transportation. This perspective seeks to highlight illustrative materials' technology developments spanning the range from nanocomposite coatings and cement sheaths for thermal insulation to the utilization of orthogonal wettability to engender separation of water-oil emulsions stabilized by endogenous surfactants extracted during SAGD, size-exclusion membranes for fractionation of bitumen, omniphobic coatings for drag reduction in pipelines and to ease oil handling in containers, solid prills obtained from partial bitumen solidification to enable solid-state transport with reduced risk of damage from spills, and nanocomposite coatings incorporating multiple modes of corrosion inhibition. Future outlooks for onsite partial upgradation are also described, which could potentially bypass the use of refineries for some fractions, enable access to a broader cross-section of refineries, and enable a new distributed chemical manufacturing paradigm.

Preparation of monosodium 2-sulfoterephthalate to make a MIL-101(Cr)–SO3H catalyst

MIL-101(Cr)-SO3H has excellent thermal and chemical stabilities, making it an ideal porous acid catalyst for many organic reactions and petrochemical industries. It's starting ligand can be lab-prepared.

Synthesis and characterization of tetraethylene pentamine functionalized MIL-101(Cr) for removal of metals from water

PURPOSE

Metal contamination in water is a worldwide persistent problem. We developed a nano-adsorbent, TEPA-MIL-101(Cr) that exhibits effective removal of heavy metals from real water samples.

METHODS

MIL-101(Cr) was synthesized under solvo-thermal condition. Then MIL-101(Cr) was dehydrated and degassed at high temperature under vacuum to generate the coordinately unsaturated sites which are used for tetraethylene pentamine (TEPA) grafting. The structures, morphologies, and compositions of the sorbents have been characterized. Langmuir and Freundlich isotherm models were applied for describing the adsorption process onto TEPA-MIL-101(Cr).

RESULTS

The successful grafting of TEPA on MIL-101(Cr) was verified by Fourier transform infrared. The results of X-ray diffraction, scanning electron microscopy, and CHN analysis show that the structure of TEPA-MIL-101(Cr) retains the original structure of MIL-101(Cr). Thermogravimetric analysis indicates thermo-stability of the adsorbent up to 300 °C. Optimal conditions for adsorption were determined as pH = 6.5 and contact time = 1 h. The adsorption capacities of TEPA-MIL-101(Cr) for Pb(II), Cu(II), Cd(II), and Co(II) from aqueous samples were 227.5, 217.7, 221.4, and 215.6 mg/g respectively, which is on average more than 8 times that of MIL-101(Cr). Analysis of Langmuir and Freundlich models for describing the adsorption isotherms of TEPA-MIL-101(Cr) reveals that the metal ions were absorbed onto TEPA-MIL-101(Cr) by a favorable physical absorption process.

CONCLUSIONS

TEPA-MIL-101(Cr) was synthesized successfully by a simple, and cost-effective method. The removal efficiency of TEPA-MIL-101(Cr) for the metal ions achieved more than 95 % in real water samples, which in addition to its thermal stability character make it a promising candidate for water treatment purposes.

Fabrication of microporous organic network@silica composite for high-performance liquid chromatographic separation of drugs and proteins

Microporous organic networks (MONs) that exhibit good stability and hydrophobicity are promising candidates for performing HPLC separation of small organic compounds. However, their applications in separating large analytes as well as biomolecules are still limited by the microporous nature of MONs. Herein, we demonstrated the fabrication of a MON-functionalized silica (MON@SiO₂ ), exhibiting micro and mesopores for the HPLC separations of small drugs as well as large analytes, such as flavones, nonsteroidal anti-inflammatory drugs (NSAIDs), endocrine disrupting chemicals (EDCs), and proteins. MON was successfully modified on SiO₂ microspheres to yield the uniform and mono-dispersed MON@SiO₂ . The separation mechanisms and performance of the MON@SiO₂ packed column were evaluated for a wide range of analytes, including neutral, acidic, basic compounds, drugs, and proteins. Compared with commercial C18 and SiO₂ -NH₂ packed columns, the proposed MON@SiO₂ column afforded superior performance in the separations of flavones, NSAIDs, EDCs, and proteins. Moreover, the MON@SiO₂ column also offered good repeatability with intraday RSDs (n = 7) of <0.1%, <2.0%, <2.3%, and <0.7% for the retention time, peak height, peak area, and half peak width, respectively, for separating EDCs. This work proved the potential of using MONs in the HPLC separations of drugs and proteins.