Porous MOF with Highly Efficient Selectivity and Chemical Conversion for CO2

Highly efficient CO2 capture and chemical fixation of a microporous (3, 36)-connected txt-type Cu(II)-MOF with multifunctional sites

Incorporating multiple functional sites in porous frameworks to enormously enhance the host-guest interactions is an effective strategy to obtain high-performance CO2 capture and chemical fixation MOF materials. Herein, we designed and constructed a microporous (3, 36)-connected txt-type Cu(II)-based MOF (HNUST-17) from dicopper(II)-paddlewheel clusters and a novel pyridine-based acylamide-linking V-shape diisophthalate ligand with amino groups. Interestingly, with a high density of multiple strong CO2-philic sites (open metal sites, acylamide and amino functionalities) integrated in the framework, which have been identified by GCMC (Grand canonical Monte Carlo) simulations and DFT (Density functional theory) calculations, HNUST-17 exhibits high and selective capture for CO2 over CH4 and N2 at ambient temperature. Moreover, HNUST-17 possesses efficiently catalytic activity and recyclability for chemical fixation of CO2 coupling with epoxides into cyclic carbonates in the presence of tetrabutylammonium bromide as the cocatalyst under mild, solvent-free conditions.

Two Sustainable Pathways of MOF-Catalyzed Room Temperature Chemical Fixation of CO2 inside Alkynes under Atmospheric Pressure

The rising atmospheric CO2 levels necessitate the development of effective materials for its mitigation. Utilization of adsorbent materials for the reversible physisorption of CO2 has a significantly less impact. Recognizing this need, herein, we present a nitrogen-rich, aqua-stable, Ag(0)-nanoparticle-doped metal-organic framework (MOF) designed for the irreversible chemical conversion of CO2 into valuable fine chemicals. We demonstrate two sustainable pathways for CO2 fixation, utilizing the catalyst, 1'@Ag NPs. The designed catalyst facilitates the cyclization of propargylic amines and alcohols under ambient temperature and pressure conditions. Remarkably, this is the first MOF-based catalyst that allows for quantitative conversion of propargylic amines into 2-oxazolidinones at room temperature with atmospheric CO2 pressure. The process successfully transforms various propargylic amines and alcohols into 2-oxazolidinones and α-alkylidene cyclic carbonates under the CO2 atmosphere. Additionally, the catalyst shows excellent recyclability, maintaining its activity and structural integrity across multiple reuse cycles. Control experiments revealed that the catalytic efficiency of 1'@Ag NPs is attributed to the highly exposed alkynophilic Ag(0) sites on its pore walls. Computational studies further elucidate the mechanistic pathway for CO2 fixation. This work highlights the potential of 1'@Ag NPs to enhance environmental sustainability by converting CO2 into valuable bioactive chemicals under mild conditions.

A novel porphyrin MOF catalyst for efficient conversion of CO2 with propargyl amines

The capture and conversion of carbon dioxide (CO2) into valuable chemical products under mild conditions is an important and challenging approach for contemporary industry. Carboxylic acid ligands are widely used in the development of functionalized metal organic framework materials due to their excellent stability. Herein, a novel mixed-metal organic framework Cu-TCPP(Fe) was assembled from iron-(Fe)-porphyrin ligands, which can efficiently catalyze the reaction of propargylic amines and CO2 to synthesize 2-oxazolidinones.

Halogen-Decorated Metal-Organic Frameworks for Efficient and Selective CO2 Capture, Separation, and Chemical Fixation with Epoxides under Mild Conditions

In the present work, three novel halogen-appended cadmium(II) metal-organic frameworks [Cd2(L1)2(4,4'-Bipy)2]n·4n(DMF) (1), [Cd2(L2)2(4,4'-Bipy)2]n·3n(DMF) (2), and [Cd(L3)(4,4'-Bipy)]n·2n(DMF) (3) [where L1 = 5-{(4-bromobenzyl)amino}isophthalate; L2 = 5-{(4-chlorobenzyl)amino}isophthalate; L3 = 5-{(4-fluorobenzyl)amino}isophthalate; 4,4'-Bipy = 4,4'-bipyridine; and DMF = N,N'-dimethylformamide] have been synthesized under solvothermal conditions and characterized by various analytical techniques. The single-crystal X-ray diffraction analysis demonstrated that all the MOFs feature a similar type of three-dimensional structure having a binuclear [Cd2(COO)4(N)4] secondary building block unit. Moreover, MOFs 1 and 2 contain one-dimensional channels along the b-axis, whereas MOF 3 possesses a 1D channel along the a-axis. In these MOFs, the pores are decorated with multifunctional groups, i.e., halogen and amine. The gas adsorption analysis of these MOFs demonstrate that they display high uptake of CO2 (up to 5.34 mmol/g) over N2 and CH4. The isosteric heat of adsorption (Qst) value for CO2 at zero loadings is in the range of 18-26 kJ mol-1. In order to understand the mechanism behind the better adsorption of CO2 by our MOFs, we have also performed configurational bias Monte Carlo simulation studies, which confirm that the interaction between our MOFs and CO2 is stronger compared to those with N2 and CH4. Various noncovalent interactions, e.g., halogen (X)···O, Cd···O, and O···O, between CO2 and the halogen atom, the Cd(II) metal center, and the carboxylate group from the MOFs are observed, respectively, which may be a reason for the higher carbon dioxide adsorption. Ideal adsorbed solution theory (IAST) calculations of MOF 1 demonstrate that the obtained selectivity values for CO2/CH4 (50:50) and CO2/N2 (15:85) are ca. 28 and 193 at 273 K, respectively. However, upon increasing the temperature to 298 K, the selectivity value (S = 34) decreases significantly for the CO2/N2 mixture. We have also calculated the breakthrough analysis curves for all the MOFs using mixtures of CO2/CH4 (50:50) and CO2/N2 (50:50 and 15:85) at different entering gas velocities and observed larger retention times for CO2 in comparison with other gases, which also signifies the stronger interaction between our MOFs and CO2. Moreover, due to the presence of Lewis acidic metal centers, these MOFs act as heterogeneous catalysts for the CO2 fixation reactions with different epoxides in the presence of tetrabutyl ammonium bromide (TBAB), for conversion into industrially valuable cyclic carbonates. These MOFs exhibit a high conversion (96-99%) of epichlorohydrin (ECH) to the corresponding cyclic carbonate 4-(chloromethyl)-1,3-dioxolan-2-one after 12 h of reaction time at 1 bar of CO2 pressure, at 65 °C. The MOFs can be reused up to four cycles without compromising their structural integrity as well as without losing their activity significantly.

Functionalization of Magnetic UiO-66-NH2 with a Chiral Cu(l-proline)2 Complex as a Hybrid Asymmetric Catalyst for CO2 Conversion into Cyclic Carbonates

In this study, a chiral [Cu(l-proline)2] complex-modified Fe3O4@SiO2@UiO-66-NH2(Zr) metal-organic framework [Fe3O4@SiO2@UiO-66-NH-Cu(l-proline)2] via multifunctionalization strategies was designed and synthesized. One simple approach to chiralize an achiral MOF-structure that cannot be directly chiralized using a chiral secondary agent like 4-hydroxy-l-proline. Therefore, this chiral catalyst was synthesized with a simple and multistep method. Accordingly, Fe3O4@SiO2@UiO-66-NH2 has been synthesized via Fe3O4 modification with tetraethyl orthosilicate and subsequently with ZrCl4 and 2-aminoterephthalic acid. The presence of the silica layer helps to stabilize the Fe3O4 core, while the bonding between Zr4+ and the -OH groups in the silica layer promotes the development of Zr-MOFs on the Fe3O4 surface, and then the surfaces of the synthesized magnetic MOFs composite are functionalized with 1,2-dichloroethane and Cu(II) complex with 4-hydroxy-l-proline, [Cu(l-proline)2] to afford the magnetically chiral nanocatalyst. Multiple techniques were employed to characterize this magnetically chiral nanocatalyst such as Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDX), powder X-ray diffraction (PXRD), circular dichroism (CD), inductively coupled plasma (ICP), thermogravimetric analysis (TGA), vibrating-sample magnetometry (VSM), and Brunauer-Emmett-Teller (BET) analyses. Moreover, a magnetically chiral nanocatalyst shows the asymmetric CO2 fixation reaction under solvent-free conditions at 80 °C and in ethanol under reflux conditions with up to 99 and 98% ee, respectively. Furthermore, the reaction mechanism was illustrated concerning the total energy of the reactant, intermediates and product, and the structural parameters were analyzed.

Coordination Unsaturation and Basic Site-Immobilized Nanochannel in a Chemorobust MOF for 3-Fold-Increased High-Temperature Selectivity and Fixation of CO2 under Mild Conditions with Nanomolar Recognition of Roxarsone

A multifaceted metal-organic framework (MOF) with task-specific site-engineered pores can promise high-temperature and moisture-tolerant capture and non-redox fixation of CO2 under mild conditions as well as ultrasensitive detection of carcinogenic contaminants in water. Herein, we report a pillar-bilayered MOF that holds a nanochannel with contrasting functionalities for both these sustainable applications with improved performance characteristics. The twofold entangled robust framework exhibits CO2 adsorption at elevated temperatures with considerable MOF-gas interaction. Interestingly, CO2 selectivity unveils nearly a 3-fold improvement upon the rise of temperature, affording a CO2/N2 value of 820 at 313 K, which outperforms many porous adsorbents. Additionally, breakthrough simulation establishes complete separation and attests the potential of this MOF in the separation of flue gas mixture. Importantly, minor CO2 loss during multiple capture-release cycles and under a relative humidity of 75% promise practical usability of the material. Density functional theory (DFT) not only portrays the atomistic level snapshots of temperature-triggered CO2 inclusion inside this microporous vessel alongside the role of diverse CO2-philic sites but also validates the basis of N2-phobicity of an azo-functionalized linker on such increased selectivity. The guest-free MOF further demonstrates non-redox and recyclable CO2 fixation with wide epoxide tolerance under solvent-free mild conditions and even works at atmospheric pressure and room temperature. The crucial roles of high-density acid-base sites in both adsorption and catalysis are supported by control experiments and by comparing the activity of an unfunctionalized MOF. The hydrolytic stability and strong luminescence signature benefit the framework in aqueous-phase selective and fast responsive detection of detrimental roxarsone (ROX) with high quenching (7.56 × 104 M-1) and very low sensitivity (68 nM). Apart from varying degrees of an energy-transfer mechanism, the fluorosensing of ROX is comprehensively supported by in-depth DFT studies that manifest alteration of MOF energy levels in the presence of organoarsenic compounds and depict MOF-analyte supramolecular interactions.

Spiral growth of multicomponent crystals: theoretical aspects

This paper presents recent advances in the theory of multicomponent crystal growth from gas or solution, focusing on the most common step-flow mechanisms: Burton-Cabrera-Frank, Chernov, and Gilmer-Ghez-Cabrera. Analytical expressions for the spiral crystal growth rate are presented, taking into account the properties of all species involved in the growth process. The paper also outlines theoretical approaches to consider these mechanisms in multicomponent systems, providing a foundation for future developments and exploration of previously unexplored effects. Some special cases are discussed, including the formation of nanoislands of pure components on the surface and their self-organization, the impact of applied mechanical stress on the growth rate, and the mechanisms of its influence on growth kinetics. The growth due to chemical reactions on the surface is also considered. Possible future directions for developing the theory are outlined. A brief overview of numerical approaches and software codes that are useful in theoretical studies of crystal growth is also given.

Redox-Active and Urea-Engineered-Entangled MOFs for High-Efficiency Water Oxidation and Elevated Temperature Advanced CO2 Separation Cum Organic-Site-Driven Mild-Condition Cycloaddition

Development of the multifaceted metal-organic framework (MOF) with in situ engineered task-specific sites can promise proficient oxygen evolution reaction (OER) and high-temperature adsorption cum mild-condition fixation of CO₂. In fact, effective assimilation of these attributes onto a single material with advance performance characteristics is practically imperative in view of renewable energy application and carbon-footprint reduction. Herein, we developed a three-fold interpenetrated robust Co(II) framework that embraces both redox-active and hydrogen-bond donor moieties inside the microporous channel. The activated MOF demonstrates notable OER catalysis in alkaline medium via quasi-reversible Co²⁺/Co³⁺ couple and unveils low overpotential with impressive 53.5 mV/dec Tafel slope that overpowers some benchmark, commercial, as well as contemporary materials. In particular, significantly increased turnover frequency (3.313 s^-1 at 400 mV) and fairly low charge-transfer resistance (3.02 Ω) compared to Co₃O₄, NiO, and majority of redox-active MOFs together with 91% Faradaic efficiency and notable framework durability after multiple OER cycles endorse high-performance water oxidation. Pore-wall decked urea groups benefit appreciable CO₂ adsorption even at elevated temperatures with considerable MOF-CO₂ interactions and exhibit recurrent capture-release cycles at diverse temperatures. Interestingly, CO₂ selectivity displays radical upsurge with temperature rise, affording 40% improved CO₂/N₂ value of 200 at 313 K, which outperforms many porous adsorbents and delineates real-time CO₂ scavenging potential. The guest-free MOF effectively catalyzes solvent-free CO₂ cycloaddition with broad substrate tolerance and satisfactory reusability under relatively mild condition. Opposed to the common Lewis acid-mediated reaction, two-point hydrogen-bonding activates the substrate, as supported from controlled experiments, juxtaposing the performance of an un-functionalized MOF and fluorescence modification-derived framework-epoxide interaction, providing valuable insights on unconventional cycloaddition route in the MOF.

Implementation of a Core-Shell Design Approach for Constructing MOFs for CO2 Capture

Adsorption-based capture of CO₂ from flue gas and from air requires materials that have a high affinity for CO₂ and can resist water molecules that competitively bind to adsorption sites. Here, we present a core-shell metal-organic framework (MOF) design strategy where the core MOF is designed to selectively adsorb CO₂, and the shell MOF is designed to block H₂O diffusion into the core. To implement and test this strategy, we used the zirconium (Zr)-based UiO MOF platform because of its relative structural rigidity and chemical stability. Previously reported computational screening results were used to select optimal core and shell MOF compositions from a basis set of possible building blocks, and the target core-shell MOFs were prepared. Their compositions and structures were characterized using scanning electron microscopy, transmission electron microscopy, and powder X-ray diffraction. Multigas (CO₂, N₂, and H₂O) sorption data were collected both for the core-shell MOFs and for the core and shell MOFs individually. These data were compared to determine whether the core-shell MOF architecture improved the CO₂ capture performance under humid conditions. The combination of experimental and computational results demonstrated that adding a shell layer with high CO₂/H₂O diffusion selectivity can significantly reduce the effect of water on CO₂ uptake.

Largely Entangled Diamondoid Framework with High-Density Urea and Divergent Metal Nodes for Selective Scavenging of CO2 and Molecular Dimension-Mediated Size-Exclusive H-Bond Donor Catalysis

Pore environment modulation with high-density polarizing groups in metal-organic frameworks (MOFs) can effectively accomplish selective and multicyclic carbon dioxide (CO₂) adsorption, whereas the incorporation of task-specific organic sites inside these porous vessels promise to evade self-quenching, solubility, and recyclability issues in hydrogen-bond donating (HBD) catalysis. However, concurrent amalgamation of both these attributes over a single platform is rare but extremely demanding in view of sustainable applications. We designed a robust diamondoid framework CSMCRI-17 (CSMCRI = Central Salt and Marine Chemicals Research Institute) from the mixed-ligand assembly of azo group-containing dicarboxylate ligand, urea-functionalized pyridyl linker, and Zn(II) nodes with specific divergent coordination. Seven-fold interpenetration to the microporous structure largely augments N-rich functionality that facilitates high CO₂ uptake in the activated form (17a) with good CO₂ selectivity over N₂ and CH₄ that outperform many reported materials. The framework displays very strong CO₂ affinity and no reduction in adsorption capacity over multiple uptake-release cycles. Benefitting from the pore-wall decoration with urea functionality from the pillaring strut, 17a further demonstrates hydrogen-bond-mediated Friedel-Crafts alkylation of indole with β-nitrostyrene under mild conditions, with multicyclic usability and excellent reactivity toward wide ranges of substituted nucleophiles and electrophiles. Interestingly, interpenetration-generated optimum-sized pores induce poor conversion to sterically encumbered substrate via molecular dimension-mediated size selectivity that is alternatively ascribed from additional control experiments and support the occurrence of HBD reaction within the MOF cavity. The catalytic path is detailed in light of the change of emission intensity of the framework by the electrophile as well as the judicious choice of the substrate, which authenticates the prime role of urea moiety-governed two-point hydrogen bonding.

Unlocking Molecular Secrets in a Monomer-Assembly-Promoted Zn-Metalated Catalytic Porous Organic Polymer for Light-Responsive CO2 Insertion

Anthropogenic carbon dioxide (CO₂) emission is soaring day by day due to fossil fuel combustion to fulfill the daily energy requirements of our society. The CO₂ concentration should be stabilized to evade the deadly consequences of it, as climate change is one of the major consequences of greenhouse gas emission. Chemical fixation of CO₂ to other value-added chemicals requires high energy due to its stability at the highest oxidation state, creating a tremendous challenge to the scientific community to fix CO₂ and prevent global warming caused by it. In this work, we have introduced a novel monomer-assembly-directed strategy to design va isible-light-responsive conjugated Zn-metalated porous organic polymer (Zn@MA-POP) with a dynamic covalent acyl hydrazone linkage, via a one-pot condensation between the self-assembled monomer 1,3,5-benzenetricarbohydrazide (TPH) and a Zn complex (Zn@COM). We have successfully explored as-synthesized Zn@MA-POP as a potential photocatalyst in visible-light-driven CO₂ photofixation with styrene epoxide (SE) to styrene carbonate (SC). Nearly 90% desired product (SC) selectivity has been achieved with our Zn@MA-POP, which is significantly better than that for the conventional Zn@TiO₂ (∼29%) and Zn@gC₃N₄ (∼26%) photocatalytic systems. The excellent light-harvesting nature with longer lifetime minimizes the radiative recombination rate of photoexcited electrons as a result of extended π-conjugation in Zn@MA-POP and increased CO₂ uptake, eventually boosting the photocatalytic activity. Local structural results from a first-shell EXAFS analysis reveals the existence of a Zn(N₂O₄) core structure in Zn@MA-POP, which plays a pivotal role in activating the epoxide ring as well as capturing the CO₂ molecules. An in-depth study of the POP-CO₂ interaction via a density functional theory (DFT) analysis reveals two feasible interactions, Zn@MA-POP-CO₂-A and Zn@MA-POP-CO₂-B, of which the latter has a lower relative energy of 0.90 kcal/mol in comparison to the former. A density of states (DOS) calculation demonstrates the lowering of the LUMO energy (EL) of Zn@MA-POP by 0.35 and 0.42 eV, respectively, for the two feasible interactions, in comparison to Zn@COM. Moreover, the potential energy profile also unveils the spontaneous and exergonic photoconversion pathways for the SE to SC conversion. Our contribution is expected to spur further interest in the precise design of visible-light-active conjugated porous organic polymers for CO₂ photofixation to value-added chemicals.

Selective and Multicyclic CO2 Adsorption with Visible Light-Driven Photodegradation of Organic Dyes in a Robust Metal-Organic Framework Embracing Heteroatom-Affixed Pores

Pore environment modulation with polarizing groups is one of the essential prerequisites for selective carbon dioxide (CO₂) adsorption in metal-organic frameworks (MOFs), wherein judicious installation of the photocatalytic feature can promise visible light-triggered degradation of toxic organic dye molecules. However, astute amalgamation of both these attributes over a single MOF is rather rare, yet much anticipated in view of sustainable applications. Pore engineering is effectively harnessed in a Zn(II)-based three-dimensional (3D) MOF, CSMCRI-16 (CSMCRI = Central Salt and Marine Chemicals Research Institute), through mixed-ligand assembly of a N-rich linker (L), 4,4'-oxybis(benzoic acid) (H₂oba) ligand, and [Zn₂(CO₂)₄N₂] paddle-wheel secondary building units (SBUs). The noninterpenetrated structure contains unbound nitrogen and accessible oxygen atom-decorated porous channels and exhibits admirable stability in diverse organic solvents, open air, and at elevated temperatures. The heteroatom-decorated porous channels facilitated excellent CO₂ uptake in the activated MOF (16a) with high selectivity over N₂ (CO₂/N₂: 155.3) at 273 K. The framework further exhibits reasonable CO₂ affinity and multicyclic CO₂ sorption recurrence without a significant loss in the uptake capacity. Benefitting from the presence of the [Zn₂(CO₂)₄N₂] cluster in conjugation with π-conjugated organic ligands, the extended 3D network revealed an optical band gap energy of 2.55 eV, which makes the MOF an efficient photocatalyst toward the degradation of the cationic dyes crystal violet (CV) and methylene blue (MB) in the presence of a simple 40 W visible light lamp without any assistance of external oxidants. The catalyst exhibits multicyclic performance and short reaction time in addition to the fact that catalytic efficiencies (CV: 97.2%, MB: 97.8%) are comparable to those of contemporary materials.

Dynamic Metal-Iodide Bonds in a Tetracoordinated Cadmium-Based Metal-Organic Framework Boosting Efficient CO2 Cycloaddition under Solvent- and Cocatalyst-Free Conditions

Due to the inherent thermodynamic stability and kinetic inertness of CO₂, heterogeneous catalytic conversion of CO₂ to cyclic carbonates often requires harsh operating conditions, high temperature and high pressure, and the addition of cocatalysts. Therefore, the development of efficient heterogeneous catalysts under cocatalyst-free and mild conditions for CO₂ conversion has always been a challenge. Herein, an infrequent tetracoordinated Cd-MOF was synthesized and used to catalyze CO₂ cycloaddition reactions efficiently without the addition of any cocatalyst, and its catalytic mechanism was systematically investigated through a series of experiments, including fluorescence analysis, X-ray photoelectron spectroscopy, microcalorimetry, and density functional theory (DFT) calculation. Cd-MOF features a 3D supermolecule structure with 1D 11.6 × 7.7 Ų channels, and the abundant Lewis acid/base and I^- sites located in the confined channel boost efficient CO₂ conversion with a maximum yield of 98.2% and a turnover number value of 1080.11 at 60 °C and 0.5 MPa, far surpassing most pristine MOF-based catalytic systems. A combined experimental and DFT calculation demonstrates that the exposed Cd(II) Lewis acid sites rapidly participate in coordination to activate the epoxides, and the resulting large steric hindrance facilitates leaving of the coordinated iodide ions in a reversibly dynamic fashion convenient for the rate-determining step ring-opening as a strong nucleophile. Such a pristine MOF catalyst with self-independent catalytic ring-opening overcomes the complicated operation limitation of the traditional cocatalyst-free MOF systems based on encapsulating/postmodifying cocatalysts, providing a whole new strategy for the development of simple, green, and efficient heterogeneous catalysts for CO₂ cycloaddition.

Designing Multicomponent Metal-Organic Frameworks with Hierarchical Structure-Mimicking Distribution for High CO2 Capture Performance

By utilizing a mixed-ligand strategy, a novel multicomponent Cu-metal-organic framework (MOF) (JLU-MOF107) has been successfully synthesized. JLU-MOF107 has an unusual hierarchical structure-mimicking distribution structure. The triangular 4,4',4″-benzene-1,3,5-triyl-tribenzoate (BTB) ligand and the binuclear Cu cluster form a threefold interpenetration layer, while the linear ligand 1,4-phenylene-4,4'-bis(1,2,4-triazole) (p-tr₂ph) and tetranuclear Cu cluster form a noninterpenetration pillared-layer structure. Then, the two types of layers are connected by tetranuclear Cu clusters to construct the final sandwichlike framework. JLU-MOF107 exhibits good water and humidity stability. Due to the presence of various active sites and pores, JLU-MOF107 shows an outstanding performance for CO₂ capture (171.0 cm³ g^-1 at 273 K). Density functional theory (DFT)-based calculations further prove the interactions between CO₂ molecules and multiple active sites. The innovative synthesis of this multicomponent structure offers a new perspective on making hierarchical porous materials and multifunctional MOFs.

CO2 uptake prediction of metal–organic frameworks using quasi-SMILES and Monte Carlo optimization

The first report of quasi-SMILES-based QSPR models for CO2 capture of MOFs based on experimental data.

Template-directed synthesis of three-dimensional metal organic framework 199-derived highly porous copper nano-foam fiber for solid-phase microextraction of some antibiotics prior to their quantification by High performance liquid chromatography

The in-situ preparation of three-dimensional MOF-199 (3D MOF-199) derived from the electrochemically prepared highly porous nano Cu foam on the surface of a flexible copper wire is reported. The 3D-Cu foam coating was used as a precursor and template for fabrication of MOF-199. The microextraction ability of the in-situ prepared 3D-MOF-199 fiber was evaluated using the prepared fiber for solid phase microextraction (SPME) of selected antibiotics including amoxicillin, azithromycin, ciprofloxacin, cefixime and gentamicin coupled to high-performance liquid chromatography with UV detection. Under the optimized condition, the calibration curves were linear in the range of 1-100 µg L ^- 1 (r² above 0.9921) for both water and urine matrices. Limits of detection and limits of quantification were 0.14-0.62 µg L ^- 1 and 0.53-2.17 µg L ^- 1 in the selected matrices, respectively. In addition, the repeatability of the method was evaluated by considering the relative standard deviation (RSD%). The intra-day and inter-day RSDs of the method with the single fiber was in the range of 2.8% to 4.9% and from 3.1% to 4.9%, respectively. Furthermore, the fiber-to-fiber reproducibility ranged from 2.9% to 5.5%. The enrichment factors were also in the range of 32 to 55. Finally, the method was successfully used for analysis of amoxicillin, azithromycin, ciprofloxacin, cefixime and gentamicin in urine samples. Relative recoveries for spiked urine samples were in the range of 90-105%.

Nanochannel {InZn}-Organic Framework with a High Catalytic Performance on CO2 Chemical Fixation and Deacetalization-Knoevenagel Condensation

The rare combination of In^III 5p and Zn^II 3d in the presence of a structure-oriented TDP^6- ligand led to a robust hybrid material of {(Me₂NH₂)[InZn(TDP)(OH₂)]·4DMF·4H₂O}_n (NUC-42) with the interlaced hierarchical nanochannels (hexagonal and cylindrical) shaped by six rows of undocumented [InZn(CO₂)₆(OH₂)] clusters, which represented the first 5p-3d nanochannel-based heterometallic metal-organic framework. With respect to the multifarious symbiotic Lewis acid-base and Brønsted acid sites in the high porous framework, the catalytic performance of activated NUC-42a upon CO₂ cycloaddition with styrene oxide was evaluated under solvent-free conditions with 1 atm of CO₂ pressure, which exhibited that the reaction could be well completed at ambient temperature within 48 h or at 60 °C within 4 h with high yield and selectivity. Moreover, because of the acidic function of metal sites and a central free pyridine in the TDP^6- ligand, deacetalization-Knoevenagel condensation of acetals and malononitrile could be efficiently facilitated by an activated sample of NUC-42a under lukewarm conditions.

A magnetic copper organic framework material as an efficient and recyclable catalyst for the synthesis of 1,2,3-triazole derivatives

In this study, a core-shell magnetic metal organic framework (MOF) catalyst was introduced based on Fe3O4 magnetic nanoparticles (MNPs) and copper organic frameworks. In this catalyst, Fe3O4 MNPs have been coated with MOFs in which copper was the inorganic nodes and 1,3,5-benzenetricarboxylic acid was the organic linkers. Then, the core-shell structures and catalytic efficiency have been confirmed properly and completely with various analyses such as FT-IR, TEM, SEM, TEM mapping, SEM mapping, EDX, PXRD, TGA, ICP and VSM. The Cu moieties in MOF and shell structures can catalyze the synthesis of 1,2,3-triazole derivatives with good to excellent yields in the presence of water as a green solvent. Moreover, this catalyst showed the high reusability due to the super paramagnetic properties.

Azo-Functionalized Zirconium-Based Metal-Organic Polyhedron as an Efficient Catalyst for CO2 Fixation with Epoxides

Chemical fixation of CO₂ as C1 source at ambient temperature and low pressure is an energy-saving way to make use of the green-house gas, but it still remains a challenge since efficient catalyst with high catalytic active sites is required. Here, a novel monoclinic azo-functionalized Zr-based metal-organic polyhedron (Zr-AZDA) has been prepared and applied in CO₂ fixation with epoxides. The inherent azo groups not only endow Zr-AZDA with good solubilization, but also act as basic sites to enrich CO₂ showing efficient synergistic catalysis as confirmed by TPD-CO₂ analysis. XPS results demonstrate that the Zr active sites in Zr-AZDA possess suitable Lewis acidity, which satisfies both substrates activation and products desorption. DFT calculation indicates the energy barrier of the rate-determining step in CO₂ cycloaddition could be reduced remarkably (by ca. 60.9 %) in the presence of Zr-AZDA, which may rationalize the mild and efficient reaction condition employed (80 °C and 1 atm of CO₂ ). The work provides an effective multi-functional cooperative method for improvement of CO₂ cycloaddition.

The difference in the CO2 adsorption capacities of different functionalized pillar-layered metal-organic frameworks (MOFs)

The excessive use of fossil energy has caused the CO2 concentration in the atmosphere to increase year by year. MOFs are ideal CO2 adsorbents that can be used in CO2 capture due to their excellent characteristics. Studies of the structure-activity relationship between the small structural differences in MOFs and the CO2 adsorption capacities are helpful for the development of efficient MOF-based CO2 adsorbents. Therefore, a series of pillar-layered MOFs with similar structural and different functional groups were designed and synthesized. The CO2 adsorption tests were carried out at 273 K to explore the relationship between the small structural differences in MOFs caused by different functional groups and the CO2 adsorption capacities. Significantly, compound 6 which contains a pyridazinyl group has a 30.9% increase in CO2 adsorption capacity compared to compound 1 with no functionalized group.

Synthesis of Bifunctional Porphyrin Polymers for Catalytic Conversion of Dilute CO2 to Cyclic Carbonates

Development of efficient solid catalysts for catalytic conversion of dilute CO2 is of extreme importance for carbon capture and utilization. We report the synthesis of bifunctional polymers co-incorporated with porphyrin-Zn as Lewis acid sites and Br- as nucleophiles for the cycloaddition of dilute CO2 with epoxides in this work. It was found that the Br-/Zn ratio has a volcano relation with the activity of bifunctional polymers in a cycloaddition reaction, indicating the synergy effect between Lewis acid sites and nucleophiles. The turnover frequency (TOF) of the bifunctional polymer is more than four-fold that of the physical mixture of tetrabutylammonium bromide and porphyrin-Zn-incorporated polymer, implying the enhanced cooperation between Br- and porphyrin-Zn in the polymer network. The bifunctional polymer with optimized Br-/Zn afforded 99% conversion, 99% selectivity, and a TOF as high as 12,000 h-1 for the cycloaddition of CO2 and propylene oxide, which is among the most active solid catalysts ever reported. Furthermore, the bifunctional polymer could efficiently catalyze the cycloaddition of epichlorohydrin with dilute CO2 (7.5% CO2 balanced by N2) even under ambient conditions, demonstrating its potential application in industrial-scale production.

Molecular engineering in a family of pillared-layered metal-organic frameworks for tuning gas adsorption behavior

In this work, inspired by a water-assisted three-dimensional supramolecular structure 1, we use a mixed-ligand strategy to form a 3D pillared-layered matrix by the introduction of linear ligands to compete against the water molecules. The resulting analogue microporous MOFs of 2-H, 2-F and 2-N, decorated with different functional groups, similarly show the CO2 uptake. Thanks to the negligible N2 adsorption capacity, enhanced selective adsorption towards CO2 is achieved in compound 2-N. That is, we present here an alternative plan for the high CO2 selective adsorption performance. In addition, the structure stability and moderate affinity for CO2 of these microporous MOFs endow them with excellent reusability.

Efficient and Highly Selective CO2 Capture, Separation, and Chemical Conversion under Ambient Conditions by a Polar-Group-Appended Copper(II) Metal-Organic Framework

A polar sulfone-appended copper(II) metal-organic framework (MOF; 1) has been synthesized from the dual-ligand approach comprised of tetrakis(4-pyridyloxymethylene)methane and dibenzothiophene-5,5'-dioxide-3,7-dicarboxylic acid under solvothermal conditions. This has been studied by different techniques that included single-crystal X-ray diffractometry, based on which the presence of Lewis acidic open-metal sites as well as polar sulfone groups aligned on the pore walls is identified. MOF 1 displays a high uptake of CO₂ over N₂ and CH₄ with an excellent selectivity (S = 883) for CO₂/N₂ (15:85) at 298 K under flue gas combustion conditions. Additionally, the presence of Lewis acidic metal centers facilitates an efficient size-selective catalytic performance at ambient conditions for the conversion of CO₂ into industrially valuable cyclic carbonates. The experimental investigations for this functional solvent-free heterogeneous catalyst are also found to be in good correlation with the computational studies provided by configurational bias Monte Carlo simulation for both CO₂ capture and its conversion.

A 2-Fold Interpenetrated Nitrogen-Rich Metal-Organic Framework: Dye Adsorption and CO2 Capture and Conversion

A bifunctional ligand strategy for modification of the functional pores is of great significance in the structural design of metal-organic frameworks (MOFs). Herein, a new 2-fold interpenetrated "pillared-layer" 3D Co-MOF, {[Co(HL)(4,4'-bipy)]·DMF·2H₂O}_n (1), was successfully synthesized by using two kinds of ligands, imidazolecarboxylic acid and pyridine. The metal-carboxylic layers are pillared by the 4,4'-bipy ligand, displaying a 3D framework with rectangular 3D channels (high BET surface of 190.9 m² g^-1 and maximum aperture of 3.9 Å) that are decorated with abundant uncoordinated N and O atoms. 1 shows good water stability and thermal stability (320 °C). The proper pores and active sites endowed 1 with a selective adsorption of Congo red in aqueous solution. In addition, a high CO₂ adsorption capacity and an excellent CO₂ chemical conversion were observed.

Microwave-Assisted Air Epoxidation of Mixed Biolefins over a Spherical Bimetal ZnCo-MOF Catalyst

Here, we report the synthesis of spherical bimetal ZnCo-MOF materials by a hydrothermal rotacrystallization method and their catalytic activity on the air epoxidation of mixed biolefins enhanced by microwaves. The structural and chemical properties of the ZnCo-MOF materials were fully characterized by XRD, IR, SEM, TG, XPS, and NH₃-TPD. The morphology of the material exhibited a three-dimensional spherical structure. From an NH₃-TPD test of the ZnCo-MOF catalyst, it could be concluded that the Zn_0.1Co₁-MOF-H-150 rpm material had the highest acidic content and the strongest acidity among the catalysts synthesized by different methods, which gave the best performance in the epoxidation of mixed biolefins. The air epoxidation reaction was carried out under atmospheric pressure and microwave conditions, in the absence of any initiator or coreducing agent. Moreover, the Zn_0.1Co₁-MOF catalyst could be recycled six times without reducing the catalytic activity significantly, which showed the stability of spherical catalyst material under microwaves.

The multifunctional design of metal–organic framework by applying linker desymmetrization strategy: synergistic catalysis for high CO2-epoxide conversion

A novel copper-organic framework was synthesized by a linker desymmetrization strategy. Synergistic catalysis with Lewis and Brønsted acid sites promoted a high catalytic efficiency towards the CO2-propylene oxide cycloaddition reaction.

A multi-functional two-dimensional Zn(ii)-organic framework for selective carbon dioxide adsorption, sensing of nitrobenzene and Cr2O72−

A novel two-dimensional coordination polymer {[(CH3)2NH2][Zn2(L)2]·DMF}n was synthesized. It exhibits good selective adsorption for CO2; moreover, it shows high selectivity and sensitivity for NB and Cr2O72− ions.

A Porous CoII-MOF for CO2 Cycloaddition and the Protective Effect against Staphylococcus aureus Systemic Infection in the Department of Ultrasound

A new metal-organic framework (MOF) based on CoII ions as nodes, [Co2(H2O)3(cada)](DMF)4, which has coordinated water molecules at the occupied CoII sites along with a suitable pore environment, was constructed by reaction of 5,5′-(9H-carbazole-2,7-diyl)diisophthalic acid (H4cada) and Co(NO3)2·6H2O in a water and DMF mixed solvent. The resulting activated MOF 1ais able to uptake considerable amounts of CO2 at room temperature, and be further used for the efficient conversion of epoxides along with CO2 into cyclic carbonates under mild conditions without a co-catalyst. To control intra-hospital cross-infection in the Department of Ultrasound, the anti-bacterial activity of the compound was assessed in a systemic Staphylococcus aureus infection mouse model. The survival rate of systemic Staphylococcus aureus infected mice after compound treatment was determined to evaluate protective effect of the compound invivo. The number of colony-forming units (CFUs) in the organs of infected mice was also counted for further verification.

Theoretical aspects of the growth of a non-Kossel crystal from vapours: role of advacancies

The growth of an arbitrary multicomponent non-Kossel crystal via the Burton–Cabrera–Frank mechanism is studied, considering the effect of advacancies and their recombination with adatoms on the surface. An analysis is...

Aminoethylimidazole ionic liquid-grafted MIL-101-NH2 heterogeneous catalyst for the conversion of CO2 and epoxide without solvent and cocatalyst

An aminoethylimidazole IL-functionalized MIL-101-NHIM-NH₂ catalyst efficiently catalyzes the cycloaddition reaction of CO₂ and epoxide without solvent and cocatalyst, owing to the synergistic effects of Cr, –NH₂ and Br⁻ active sites.

A binuclear Co-based metal-organic framework towards efficient oxygen evolution reaction

The search for low-cost and high-performance electrocatalysts for oxygen evolution reaction (OER) has aroused enormous research interest in the last few years. Reported herein is the topotactic construction of a binuclear Co-based metal-organic framework (Co2-tzpa) using a solvothermal reaction. Prominently, as a porous catalyst, Co2-tzpa holds its activity for at least 25 hours and exhibits low OER overpotentials of 336 and 396 mV to achieve the current density of 10 mA cm-2 in 1 M KOH and 0.1 M KOH, respectively. The excellent OER performance should be attributed to each cobalt site coordinated with two tetrazolate N atoms.

Metal Organic Framework-Polyethersulfone Composite Membrane for Iodine Capture

A variety of metal organic frameworks (MOFs) were synthesized and evaluated for their iodine adsorption capacity. Out of the MOFs tested, ZIF-8 showed the most promising result with an iodine vapor uptake of 876.6 mg/g. ZIF-8 was then incorporated into a polymer, polyethersulfone (PES), at different proportions to prepare mixed matrix membranes (MMMs), which were then used to perform further iodine adsorption experiments. With a mixing ratio of 40 wt % of ZIF-8, the iodine adsorption capacity reached 1387.6 mg/g, wherein an astounding 60% improvement in adsorption was seen with the MMMs prepared compared to the original ZIF-8 powder.

Unprecedented High Temperature CO2 Selectivity and Effective Chemical Fixation by a Copper-Based Undulated Metal-Organic Framework

Post- and precombustion CO₂ capture and separation are the vital challenges from industrial viewpoint, as the accessible technologies are not cost-effective and cumbersome. Thus, the development of functional metal-organic frameworks (MOFs) that are found to be promising materials for selective CO₂ capture, separation, and conversion is gaining an importance in the scientific world. Based on the strategic design, a new functionalized triazine-based undulated paddle-wheel Cu-MOF (1), {[Cu(MTABA)(H₂O)]·4H₂O·2EtOH·DMF}_n (where, H₂MTABA = 4,4'-((6-methoxy-1,3,5-triazine-2,4-diyl)bis(azanediyl))dibenzoic acid), has been synthesized under solvothermal conditions and fully characterized. MOF 1 contains a one-dimensional channel along the a-axis with pore walls decorated with open metal sites, and multifunctional groups (amine, triazine, and methoxy). Unlike other porous materials, activated 1 (1') possesses exceptional increment in CO₂/N₂ and CO₂/CH₄ selectivity with increased temperature calculated by the ideal adsorbed solution theory. With an increase in temperature from 298 to 313 K, the selectivity of CO₂ rises from 350.3 to 909.5 at zero coverage, which is unprecedented till date. Moreover, 1' behaves as a bifunctional heterogeneous catalyst through Lewis acid (open metal) and Brönsted acid sites to facilitate the chemical fixation of CO₂ to cyclic carbonates under ambient conditions. The high selectivity for CO₂ by 1' even at higher temperature was further corroborated with configurational bias Monte Carlo molecular simulation that ascertains the multiple CO₂-philic sites and epoxide binding sites in 1' to further decipher the mechanistic pathway.

Artificial Metalloenzymes: Recent Developments and Innovations in Bioinorganic Catalysis

Cellular life is orchestrated by the biochemical components of cells that include nucleic acids, lipids, carbohydrates, proteins, and cofactors such as metabolites and metals, all of which coalesce and function synchronously within the cell. Metalloenzymes allow for such complex chemical processes, as they catalyze a myriad of biochemical reactions both efficiently and selectively, where the metal cofactor provides additional functionality to promote reactivity not readily achieved in their absence. While the past 60 years have yielded considerable insight on how enzymes catalyze these reactions, a need to engineer and develop artificial metalloenzymes has been driven not only by industrial and therapeutic needs, but also by innate human curiosity. The design of miniature enzymes, both rationally and through serendipity, using both organic and inorganic building blocks has been explored by many scientists over the years and significant progress has been made. Herein, recent developments over the past 5 years in areas that have not been recently reviewed are summarized, and prospects for future research in these areas are addressed.