Multifunctional Biomass-Based Ionic Liquids/CuCl-Catalyzed CO2-Promoted Hydration of Propargylic Alcohols: A Green Synthesis of α-Hydroxy Ketones.

α-Hydroxy ketones are a class of vital organic skeletons that generally exist in a variety of natural products and high-value chemicals. However, the traditional synthetic route for their production involves toxic Hg salts and corrosive H2SO4 as catalysts, resulting in harsh conditions and the undesired side reaction of Meyer-Schuster rearrangement. In this study, CO2-promoted hydration of propargylic alcohols was achieved for the synthesis of various α-hydroxy ketones. Notably, this process was catalyzed using an environmentally friendly and cost-effective biomass-based ionic liquids/CuCl system, which effectively eliminated the side reaction. The ionic liquids utilized in this system are derived from natural biomass materials, which exhibited recyclability and catalytic activity under 1 bar of CO2 pressure without volatile organic solvents or additives. Evaluation of the green metrics revealed the superiority of this CuCl/ionic liquid system in terms of environmental sustainability. Further mechanistic investigation attributed the excellent performance to the ionic liquid component, which exhibited multifunctionality in activating substrates, CO2 and the Cu component.

The Nature of Structural Defects in ZIF-8 Revealed with 1H and 31P MAS NMR and X-Ray Absorption Spectroscopy.

The metal-organic frameworks (MOFs) attract interest as potential catalysts whose catalytic properties are driven by defects. Several methods have been proposed for the defects-inducing synthesis of MOFs. However, the active species formed on the defective sites remain elusive and uncharacterized, as the spectroscopic fingerprints of these species are hidden by the regular structure signals. In this work, we have performed the synthesis of ZIF-8 MOF with defect-inducing procedures using fully deuterated 2-methylimidazolate ligands to enhance the defective sites' visibility. By combining 1H and 31P MAS NMR spectroscopy and X-ray absorption spectroscopy, we have found evidence for the presence of different structural hydroxyl Zn-OH groups in the ZIF-8 materials. It is demonstrated that the ZIF-8 defect sites are represented by Zn-OH hydroxyl groups with the signals at 0.3 and -0.7 ppm in the 1H MAS NMR spectrum. These species are of basic nature and may be responsible for the catalytic activity of the ZIF-8 material.

Recent Progress on the Synthesis and Modified Strategies of Zeolitic-Imidazole Framework-67 Towards Electrocatalytic Oxygen Evolution Reaction.

As a class of metal-organic framework, the zeolitic-imidazole framework-67 is constructed from bridging cobalt ions and 2-methylimidazole. The high content of abundant active cobalt species, uniform structure, ultrahigh porosity, and large surface area show the potential for multiple catalytic applications, especially electrocatalytic oxygen evolution reaction (OER). The design and synthetic strategies of catalyst-based ZIF-67 that approach the maximized catalytic performance are still challenging in further development. Herein, the current progress strategy on the structural design, synthetic route, and functionalization of electrocatalysts based on ZIF-67 to boost the catalytic performance of OER is reviewed. Besides, the structurally designed catalyst from various fabricated strategies corresponding to enhancing catalytic activity is discussed. The emphasized review for understanding design and synthetic structure with catalytic performance could guide researchers in further developing catalyst-based ZIF-67 for improving the efficient electrocatalytic OER.

Metal-organic frameworks for upgrading biogas via CO2 adsorption to biogas green energy.

In the midst of the global climate change phenomenon, mainly caused by fossil fuel burning to provide energy for our daily life and discharge of CO2 into the atmosphere, biogas is one of the important renewable energy sources that can be upgraded and applied as a fuel source for energy in daily life. The advantages of the production of hybrid materials, metal-organic framework (MOF) adsorbents, expected for the biogas upgrading, rely on the bulk separation of CO2 under near-ambient conditions. This review highlights the challenges for MOF adsorbents, which have the greatest upgrading abilities for biogas via selective passage of methane. The key factors improving the ideal MOF materials for these high CO2 capture and selectivity uses for biogas upgrading to produce bio-methane and reduce fossil-fuel CO2 emission will be discussed.

Tuning Coordination in ZIF-67 Through the Solid-State Thermal Synthesis for Balancing Structural Stability and Catalytic Reactivity.

Tailor-made unsaturated coordination of metal ions or organic linkers in zeolitic imidazole frameworks (ZIFs) has great potential in tuning the ZIFs' properties and reactivity for their applications. Taking advantage of the solid-state thermal (SST) method as a facile and eco-friendly synthesis method, the rational coordination of metal ions with imidazole ligands in ZIF-67 through the SST method is investigated. The rational precursor ratio (metal-to-ligand source) under the solvent-free SST method emerges as a perfect strategy to tune the coordinately unsaturated sites within the ZIF-67 frameworks. Different analysis techniques, computational methods (DFT), and catalytic model reactions examine unsaturated coordination in ZIF-67 materials (defect structures). The unsaturated coordination provides unique characteristic properties on materials with excellent catalytic performance. However, the higher reactive properties are negotiated with weaker structural stability on materials. In addition, the post-SST approach is applied to enable rational coordination and modify the pristine ZIF-67 materials. The post-SST method rearranges and modifies coordination in the framework of materials. These findings are crucial to understanding the role of the uncoordinated degree to balance with structural stability based on ZIF-67, which is critical for effective heterogeneous catalysts.

Correlating Single-Atomic Ruthenium Interdistance with Long-Range Interaction Boosts Hydrogen Evolution Reaction Kinetics.

Correlated single-atom catalysts (c-SACs) with tailored intersite metal-metal interactions are superior to conventional catalysts with isolated metal sites. However, precise quantification of the single-atomic interdistance (SAD) in c-SACs is not yet achieved, which is essential for a crucial understanding and remarkable improvement of the correlated metal-site-governed catalytic reaction kinetics. Here, three Ru c-SACs are fabricated with precise SAD using a planar organometallic molecular design and π-π molecule-carbon nanotube confinement. This strategy results in graded SAD from 2.4 to 9.3 Å in the Ru c-SACs, wherein tailoring the Ru SAD into 7.0 Å generates an exceptionally high turnover frequency of 17.92 H2 s-1 and a remarkable mass activity of 100.4 A mg-1 under 50 and 100 mV overpotentials, respectively, which is superior to all the Ru-based catalysts reported previously. Furthermore, density functional theory calculations confirm that Ru SAD has a negative correlation with its d-band center owing to the long-range interactions induced by distinct local atomic geometries, resulting in an appropriate electrostatic potential and the highest catalytic activity on c-SACs with 7.0 Å Ru SAD. The present study promises an attractive methodology for experimentally quantifying the metal SAD to provide valuable insights into the catalytic mechanism of c-SACs.

Combined experimental and simulation study on H2 storage in oxygen and nitrogen co-doped activated carbon derived from biomass waste: superior pore size and surface chemistry development.

In this study, heteroatom (O, N)-doped activated carbon (AC) is produced using urea and KOH activation from abundant and cost-effective biomass waste for H2 storage. The O and N co-doped AC exhibits the highest specific surface area and H2 storage capacity (2.62 wt%), increasing by 47% from unmodified AC at -196 °C and 1 bar. Surface modification helps develop superior pore sizes and volumes. However, the original AC is superior at lower pressures (<0.3 bar) because of its suitable pore width. This observation is then explained by molecular simulations. Optimal pore widths are 0.65 nm at <0.3 bar and 0.95-1.5 nm at pressures in moderate range (0.3-15 bar). Superior pore sizes are observed in the range of 0.8-1.3 nm at 1 bar, enhancing performance with co-doped AC to achieve uptake superior to that of other ACs described in the literature. However, above 15 bar, pore volume dominates capacity over pore width. Among the O and N groups, pyridinic-N oxide is the most substantial, playing a vital role at low and moderate pressures. These findings propose a strategy for superior H2 storage in porous carbons under various pressure conditions.

Single-thermal synthesis of bimetallic Co/Zn@NC under solvent-free conditions as an efficient dual-functional oxygen electrocatalyst in Zn-air batteries.

A straightforward in situ thermal (IST) method is developed to synthesize bimetallic Co/Zn embedded in nitrogen-doped three-dimensional carbon (CoZn@NC_IST). The facile IST process is a single-step thermal treatment of a mixture of metals (Co/Zn) and 2-methylimidazole precursors under solvent-free conditions. This straightforward method is advantageous over the traditional synthesis derived from CoZn-ZIF (CoZn@NC_Solv). During the IST method, the bimetallic Co/Zn bridged with 2-methylimidazole forming zeolitic-imidazole frameworks (ZIFs) under low-temperature (<200 °C) conditions before being de-coordinated and sacrificed their structure into a carbon material at high temperature (>500 °C). Loading zinc into the mixture of precursors contributed to the metal distribution and increased the surface area compared with the sample without zinc (Co@NC_IST). CoZn@NC_IST exhibits a bifunctional electrocatalytic ability for the ORR (0.855 V@E1/2) and OER (overpotential of 325 mV@10 mA cm-2). Applying CoZn@NC_IST in a zinc-air battery confirmed its excellent and effective dual-function electrocatalytic performance. Herein, using the advanced single-step method of IST in the absence of any solvent, we provide a powerful and green synthesis of an electrocatalyst that is a potential candidate for industrial applications.

Strategies for induced defects in metal-organic frameworks for enhancing adsorption and catalytic performance.

Metal-organic frameworks (MOFs) have emerged among porous materials. The designable structure and specific functionality make them stand out for diverse applications. In conceptual MOF, the metal ions/clusters and organic ligands are perfectly coordinated to form a network framework as an ideal crystal structure. However, in reality, uncoordinated metal and ligands or vacancies in the crystal structure are already confirmed and known as defects. Defects in the MOF structure have inner effects on the functional properties and uniquely influence the MOF's applications. Thus, besides various methods for MOF development, the strategy of structural design, and functionalization, manufacturing defects in MOF could be another modification strategy of MOFs. These tailorable strategies to induce defects in the MOF structure not only change the MOFs properties but also improved the performance in various applications. This review overviews the progress of strategies for inducing structural defects, aiming to provide knowledge for defective MOFs. Subsequently, the influence of these methods on the MOFs properties and applications, especially adsorption and catalysis, were discussed.

Simultaneous transformation of 2D to 3D and doped metal transitions of zeolitic imidazole frameworks under solid phase and free-solvent conditions.

The post-thermal treatment (PTT) method was applied for crystal transformation on the structure of zeolitic imidazolate frameworks (ZIFs) from 2D to 3D under solvent-free conditions. The investigation was performed based on bridging of the cobalt ions by the 2-methylimidazole linker to form the ZIF structure. Extensive characterization revealed that the reaction mechanism was a transformation in the solid crystal phase and resulted from the de-coordination of the framework and reformation of the crystalline structure. In addition, the PTT method opens the opportunity to simultaneously dope transition metals (Zn, Co, Fe, Ni, and Mn) in the framework during the transformation of ZIFs. The materials with doped metals showed enhanced properties and excellent performance for applications including gas adsorption, dye degradation, and the catalytic activity of CO2 fixation.

Kinetic modeling of heterogeneous esterification reaction using initial reaction rate analysis: data extraction and evaluation of mass transfer criteria.

This data article provides detailed guidance to obtain heterogeneous reaction rate expressions and the corresponding initial reaction rates and their application. Explanation is provided to deal with specific criteria to rule out internal and external concentration gradients, so that the usage of intrinsic catalytic data is guaranteed. Overall, the main goal is to provide an easy tool to evaluate both aforementioned results by simple plug-and-play of available reaction data.

Cross-Linked Mixed-Matrix Membranes Using Functionalized UiO-66-NH2 into PEG/PPG-PDMS-Based Rubbery Polymer for Efficient CO2 Separation.

Mixed-matrix membranes (MMMs) with an ideal polymer-filler interface and high gas separation performance are very challenging to fabricate because of incompatibility between the fillers and the polymer matrix. This work provides a simple technique to prepare a series of cross-linked MMMs (xMMM@n) by covalently attaching UiO-66-NB metal-organic frameworks (MOFs) within the PEG/PPG-PDMS copolymer matrix via ring-opening metathesis polymerization and in situ membrane casting. The norbornene-modified MOF (UiO-66-NB) is successfully copolymerized and dispersed homogeneously into a PEG/PPG-PDMS matrix because of very fast polymer formation and strong covalent interaction between MOFs and the rubbery polymer. A significant improvement in gas permeability is achieved in membranes up to a 5 wt % MOF loading compared to the pristine polymer membrane without affecting selectivity. The CO2/N2 separation performance of xMMM@1, xMMM@3, and xMMM@5 with 1, 3, and 5 wt % MOF loading, respectively, surpassed Robeson's 2008 upper bound. In addition, the best performing membrane, xMMM@3 (PCO2 = 585 Barrer and CO2/N2 ∼53), approaches the 2019 upper bound, indicating that the cross-linked MMMs (xMMM@n) are very promising for CO2 separation from flue gas. The experimental results of our study were evaluated and are supported by theoretical data obtained using the Maxwell model for MMMs. Moreover, the developed MMMs, xMMM@ns, displayed outstanding antiplasticization performance at pressures of up to 25 atm and very stable antiaging performance for up to 11 months with good temperature switching behaviors.

Thermochemical transformation in the single-step synthesis of zeolitic imidazole frameworks under solvent-free conditions.

An environmentally friendly and economical route for the synthesis of zeolitic imidazole frameworks (ZIFs) was developed based on the thermal treatment of mixed solid precursors in the absence of solvent and additive compounds. This facile, rapid, and one-step synthetic method involves the heat treatment of a mixture of solid precursors (metal and linker). The solid mixture was transformed into a porous crystalline material without post-treatment and in the absence of any solvent. The synthesized materials are nanocrystals (200-500 nm) with sodalite topology, similar to conventionally prepared ZIFs. The properties of the synthesized materials were evaluated using powder X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, porosity and surface area analysis, gas adsorption, and thermal gravimetric analysis. The metal-oxide precursor, which is typically considered to be inert in the context of chemical synthesis, was readily transformed into a ZIF using this thermochemical method. The developed solvent-free, fast, and eco-friendly synthetic method for the preparation of porous ZIFs may be applicable for large-scale industrial synthesis.

Tunable Metal⁻Organic Frameworks for Heat Transformation Applications.

Metal⁻Organic Frameworks (MOFs) are a subclass of porous materials that have unique properties, such as varieties of structures from different metals and organic linkers and tunable porosity from a structure or framework design. Moreover, modification/functionalization of the material structure could optimize the material properties and demonstrate high potential for a selected application. MOF materials exhibit exceptional properties that make these materials widely applicable in energy storage and heat transformation applications. This review aims to give a broad overview of MOFs and their development as adsorbent materials with potential for heat transformation applications. We have briefly overviewed current explorations, developments, and the potential of metal⁻organic frameworks (MOFs), especially the tuning of the porosity and the hydrophobic/hydrophilic design required for this specific application. These materials applied as adsorbents are promising in thermal-driven adsorption for heat transformation using water as a working fluid and related applications.

Data for the synthesis of ß-oxopropylcarbamates from propargylic alcohols, secondary amines and CO2 catalyzed by a recyclable AgBr/ionic liquid system under ambient pressure.

Data presented here are related with the research article entitled "Synthesis of ß -oxopropylcarbamates in a recyclable AgBr/ionic liquid catalytic system: An efficient assembly of CO2 under ambient pressure" (Song et al., 2018) [1]. In this data article, the general synthetic procedures of ß-oxopropylcarbamates through the three-component reaction of propargylic alcohols, secondary amines and carbon dioxide (CO2) catalyzed by a recyclable AgBr/ionic liquid (IL) system under mild pressure are described. Furthermore, the process for recycling the catalysts is supplied as well. Specifically, the investigative data for the temperature, amount of ILs, reaction time as well as the state of silver in the system are also reported. Finally, all the target products are confirmed by 1H NMR, 13C NMR, and high-resolution mass spectroscopy (HR-MS).

MoO3NPs/ZIF-8 composite material prepared via RCVD for photodegradation of dyes.

Toxic wastewaters from the textile industry have made its way into rivers and other waterways, posing a serious health treat on both human and wildlife. Herein, this data set presents the potential use of MoO3 nanoparticles supported on ZIF-8 in the photodegradation of a cationic dye molecule. The data presented in this article report a concise description of experimental conditions for the spray-dried ZIF-8 synthesis and subsequent deposition of MoO3 nanoparticles via rotary chemical vapor deposition (RCVD). The photodegradation and analysis data reviled that the MoO3-NPs@ZIF-8 3 wt% displayed the ability of degrading methylene blue up to 82% and 95% after 180 and 300 min, respectively.

Ring-Opening Polymerization of l-Lactide to Cyclic Poly(Lactide) by Zeolitic Imidazole Framework ZIF-8 Catalyst.

The catalytic activity of ZIF-8 in the ring-opening polymerization of l-lactide without solvents or cocatalysts is presented for the first time. Two different synthetic strategies have been applied for synthesizing ZIF-8, either under solvothermal condition or by spray-drying procedure. Their catalytic activities are found to be correlating with the presence of open active sites in ZIF-8 structure. The structural defects that afford active acid and basic sites are supposed to cooperatively catalyze the reaction. ZIF-8 assembled by spray-drying technique, displays a superior catalytic activity at temperature of 160 °C, leading to the formation of high molecular weight cyclic polylactide. The ZIF-8 catalysts could be recycled and reused without any significant loss of catalytic activity.

CO2 Cycloaddition to Epoxides by using M-DABCO Metal-Organic Frameworks and the Influence of the Synthetic Method on Catalytic Reactivity.

A series of high-quality M2(BDC)2(DABCO) metal-organic frameworks (abbreviated as M-DABCO; M=Zn, Co, Ni, Cu; BDC=1,4-benzene dicarboxylate; DABCO=1,4-diazabicyclo[2.2.2]octane), were synthesized by using a solvothermal (SV) method, and their catalytic activity for the cycloaddition of CO2 to epoxides in the absence of a co-catalyst or solvent was demonstrated. Of these metal-organic frameworks (MOFs), Zn-DABCO exhibited very high activity and nearly complete selectivity under moderate reaction conditions. The other members of this MOF series (Co-DABCO, Ni-DABCO, and Cu-DABCO) displayed lower activity in the given sequence. Samples of Zn-DABCO, Co-DABCO, and Ni-DABCO were recycled at least three times without a noticeable loss in catalytic activity. The reaction mechanism can be attributed to structural defects along with the acid-base bifunctional characteristics of these MOFs. Moreover, we illustrate that the synthetic method of M-DABCO influences the yield of the reaction. In addition to the SV method, Zn-DABCO was synthesized by using spray drying due to its industrial attractiveness. It was found that the synthesis procedure clearly influenced the crystal growth and thus the physicochemical properties, such as surface area, pore volume, and gas adsorption, which in turn affected the catalytic performance. The results clarified that although different synthetic methods can produce isostructural MOFs, the application of MOFs, especially as catalysts, strongly depends on the crystal morphology and textural properties and, therefore, on the synthesis method.

Water Oxidation by In Situ Generated [RuII (OH2 )(NCNHC O)(pic)2 ].

A dinuclear ruthenium complex [RuII (NCNHC O)(pic)2 ]22+ (2) was firstly prepared and characterized spectroscopically and electrochemically. Instead of the conventional ligand exchange, complex 2 dissociates in situ to afford two single-site Ru aqua complexes, [RuII (OH2 )(NCNHC O)(pic)2 ]+ , which mediates water oxidation through proton-coupled electron transfer events. In electrokinetic studies, complex 2 demonstrated a TOF of 150.3 s-1 comparable to those state-of-the-art catalysts at neutral conditions. TONs of 2173 and 217 were attained in chemical and photochemical water oxidation when 2 was used as a catalyst, exhibiting good stability. Notably, a TOF of 1.3 s-1 was achieved at CAN-driven water oxidation, which outperformed most of the reported single-site Ru complexes, indicating that complex 2 is one of most active water oxidation catalysts (WOCs) to date. The unique coordination configuration and outstanding catalytic performance of complex 2 might shed light on the design of novel molecular WOCs.