Zn-based Metal-organic Framework Research Articles

Constructing Zn-based MOF-MXene nanoarchitectures to stabilize ultrafine Pt nanocrystals with enhanced methanol oxidation performance

Although the development of direct methanol fuel cell technology is regarded as one rational option to against severe energy crises and environmental pollution, the low efficiency and considerable costs of current Pt-based anode catalysts largely impede the broad-scale commercialization. Herein, a convenient bottom-up approach is developed to the spatial construction of ultrafine Pt nanocrystals stabilized on a porous heterojunction matrix built from Zn-based metal organic frameworks and Ti3C2Tx MXene nanolamellas (Pt/ZIF-Ti3C2Tx) through the stepwise solvothermal reactions. The intercalation of metal organic frameworks produces plentiful cavities and channels for the dispersion and immobilization of small-sized Pt nanoparticles, while the incorporation of Ti3C2Tx nanosheets optimizes the Pt electronic structure and ensures a high electron conductivity. As a consequence, the as-acquired Pt/ZIF-Ti3C2Tx nanoarchitectures manifest exceptional electrocatalytic methanol oxidation abilities in terms of a large electrochemically active surface area of 110.5 m2 g−1, a high mass activity of 1900.1 mA mg−1, and preferable long-term stability, all of which are significantly superior to those of conventional Pt/carbon and Pt/unmodified Ti3C2Tx catalysts.

Gas-phase continuous synthesis of metal-organic framework-derived hybrid catalysts for combined CO2 and CO hydrogenation to methanol

Aerosol-based continuous synthesis for metal–organic framework (MOF) derived catalyst materials, in combination with real-time gas-phase electrophoresis for material characterization, is demonstrated for methanol production via combined CO2 and CO hydrogenation. Cu-based and Zn-based MOF colloids were prepared as the templates for the synthesis of Cu-ZnO catalysts supported on either Al2O3 or CeO2. The results showed the incorporation of real-time gas-phase electrophoresis enabled traceability of continuous catalyst production. Optimal selectivity of 90.52 %, and space–time yield of 7.50 mmol gcat−1h−1 were achievable in the methanol production. Interestingly, the space–time yield of methanol was shown to be linearly proportional to metal surface area of the catalyst. This study demonstrated significant advances in the continuous production of MOF-derived hybrid catalysts through aerosol-phase synthesis with real-time characterization. The high catalytic performance of the developed materials in the combined CO2 and CO hydrogenation to methanol bears promise for applications in the field of CO2 utilization.

Detection of acetamiprid residues in vegetables by a self-enhanced bimetallic luminescent MOF-based electrochemiluminescence-electrochemistry dual-mode aptasensor

In this study, a dual-mode aptasensor based on the competition mechanism was constructed to detect acetamiprid (ACE) residues in vegetables. With 3,5-dicarboxyphenylboronic acid (5-bop) as a ligand, a bimetallic RuZn-based metal-organic framework (RuZn-MOF) was synthetized by applying a hydrothermal method to achieve efficient electrochemiluminescence (ECL) and electrochemistry (EC) dual-mode detection of ACE. Compared with the monometallic Zn-based metal-organic framework (Zn-MOF) of the same structure, the bimetallic RuZn-MOF exhibited a greater ability to transfer electrons due to the synergistic effect between different metal and the 5-bop ligand. Meanwhile, the complementary DNA (cDNA) probe for bonding the ACE aptamer was modified with ferrocene (Fc) and methylene blue (MB). When the target pesticide of ACE was present, ACE competed with the cDNA probe, so that the ECL achieved the "signal on" and the EC achieved the "signal off". ECL and EC detection being combined, the results showed that the two detection methods corroborated each other and worked synergistically, i.e., they effectively reduced the systematic errors and background signals, and improved the reliability of the detection. The linear ranges of the ECL and EC aptasensors were 1 pg/mL-1 μg/mL with the limit of detection (LOD) of 0.33 pg/mL, and 1 fg/mL-1 ng/mL with LOD of 0.33 fg/mL (S/N=3), respectively. The dual-mode strategy had good stability and specificity, providing some valuable support for the detection and analysis of other substances.

A highly sensitive and selective Zn-based luminescent MOF for specific detection of trinitrotoluene in aqueous phase

The existence of nitroaromatic compounds, specifically 2,4,6-trinitrotoluene (TNT), in water reservoirs poses significant health risks, necessitating robust detection and monitoring strategies. In this study, we leverage the exceptional properties of the previously synthesized metal-organic framework (MOF), PUC2 as a highly luminescent probe for selective and sensitive detection of TNT in aqueous media. PUC2 exhibits remarkable luminescence, emitting a vivid blue light, making it an ideal candidate for TNT detection. Our investigations reveal that PUC2 demonstrates outstanding sensitivity, achieving an impressive detection limit of 0.145 μM towards TNT which can be attributed to the robust probe-analyte interactions evident from the quenching constant (Ksv) value of 0.18 × 104M−1. An intriguing aspect of PUC2 is its adaptability to a wide pH range, maintaining its sensing capabilities effectively in aqueous phase with pH levels ranging from 4 to 11. The predominant quenching mechanism in this context appears to be photoinduced electron transfer (PET), with an additional enhancement through Forster resonance energy transfer (FRET). The unique combination of structural features and exceptional sensing capabilities of PUC2 opens up new avenues for environmental monitoring and security applications, highlighting its potential as a highly effective luminescent sensor for detecting hazardous substances like TNT.

Recrystallization strategy of ZnBTC nanowires and derivates for supercapacitor application

Nanoarchitecturing of metal–organic frameworks (MOFs) to endow abundant exposed surface and active sites, shorter diffusion pathways, and improved electrical conductivity are the main interest of the current research. In this study, we propose a recrystallization strategy to nanoarchitecture Zn-based MOF (ZnBTC) by exploiting the weakly coordinating nature of alcohols in ZnBTC. The recrystallized ZnBTC successfully gives rise to a unique nanoarchitecture with abundant nanowires of various aspect ratios. The DFT calculations on the chemical potential and hardness of alcohols explain the effect of different alcohols on the recrystallization of ZnBTC. The as-prepared nanowire ZnBTC (N-ZnBTC) is converted to its carbonaceous form which demonstrates the unique nanoarchitecture consisting of numerous nanowires to achieve a promising energy storage performance as a supercapacitor electrode.

Comparative Analysis of Proton Conductivity in Two Zn-Based MOFs Featuring Sulfate and Sulfonate Functional Groups.

Metal-organic frameworks (MOFs) have shown promising potential as proton-conducting materials due to their tunable structures and high porosity. In this study, two novel MOFs had been successfully synthesized, one containing sulfate groups (MOF-1; [Zn4(TIPE)2(SO4)4(H2O)]·5H2O) and the other containing sulfonate groups (MOF-2; [Zn2(TIPE)(5-sip)(NO3)0.66]·0.34NO3·17.5H2O) (TIPE = 1,1,2,2-tetrakis(4-(1H-imidazole-1-yl)phenyl)ethene, H35-sip = 5-sulfoisophthalicacid), and the effect of the two groups on the proton conductivity of Zn-based MOFs had been investigated and compared for the first time. The proton conductivity of these MOFs was systematically measured at different temperatures and humidity conditions. Remarkably, the results revealed significant differences in proton conductivity between the two sets of MOFs. At 90 °C and 98% RH, MOF-1 and MOF-2 achieved optimal proton conductivity of 4.48 × 10-3 and 5.69 × 10-2 S·cm-1, respectively. This was due to the structural differences arising from the presence of different functional groups, which subsequently affected the porosity and hydrophilicity, thereby influencing the proton conductivity. Overall, this comparative study revealed the influence of sulfate and sulfonate groups on the proton conductivity of Zn-based MOFs. This research provided a feasible idea for the development of advanced MOF materials with enhanced proton conductivity and opened up new possibilities for their application in proton devices.

Application of Functionalized Zn-Based Metal-Organic Frameworks (Zn-MOFs) with CuO in Heterocycle Synthesis via Azide-Alkyne Cycloaddition.

The main goal of this article is to discuss the expansion of click chemistry. A new catalyst composed of CuO nanoparticles embedded in Zn-MOF with the ligand 2,4,6-tris(4-carboxyphenoxy)-1,3,5-triazine (H3L) is presented. The incorporation of CuO nanoparticles into the Zn-MOF structure led to desirable morphology and catalytic properties. The designed catalyst was evaluated for its catalytic role in the multicomponent reaction and copper-catalyzed azide-alkyne cycloaddition (CuAAC) for preparation of triazole rings with 80-91% yield. The catalyst demonstrated an appealing architecture and exhibited robustness, high efficiency, and environmental friendliness. Characterization of the catalyst was performed using various techniques, including Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopes (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), elemental mapping, and X-ray diffraction (XRD). The results suggest that this novel catalyst has the potential to be a valuable tool in the development of new synthetic approaches for a wide range of applications.

Manipulating the Spin State of Co Sites in Metal-Organic Frameworks for Boosting CO2 Photoreduction.

Photocatalytic CO2 reduction holds great potential for alleviating global energy and environmental issues, where the electronic structure of the catalytic center plays a crucial role. However, the spin state, a key descriptor of electronic properties, is largely overlooked. Herein, we present a simple strategy to regulate the spin states of catalytic Co centers by changing their coordination environment by exchanging the Co species into a stable Zn-based metal-organic framework (MOF) to afford Co-OAc, Co-Br, and Co-CN for CO2 photoreduction. Experimental and DFT calculation results suggest that the distinct spin states of the Co sites give rise to different charge separation abilities and energy barriers for CO2 adsorption/activation in photocatalysis. Consequently, the optimized Co-OAc with the highest spin-state Co sites presents an excellent photocatalytic CO2 activity of 2325.7 μmol·g-1·h-1 and selectivity of 99.1% to CO, which are among the best in all reported MOF photocatalysts, in the absence of a noble metal and additional photosensitizer. This work underlines the potential of MOFs as an ideal platform for spin-state manipulation toward improved photocatalysis.

Sensing of hyperprolinemia biomarker and its recognition in biological sample through “turn-on” event by Zn-based metal-organic framework

A hydrogen bonded ability metal organic framework (MOF, 1Zn) is used for the ultra-sensitive “turn-on” detection of hyperprolinemia biomarker with ultrafast (within 5 s) colorimetric response making the first MOF based hyperprolinemia biomarker sensor. The detection limit (4.46 ppb) is outperformed compared to all contemporary hyperprolinemia biomarker based sensors. Further, the sensor showed the recognition of biomarker in biological sample (human saliva). The detection of biomarker is also realized through colorimetric response (solution based and paper strip method). The mechanism of sensing is established through the electron transfer and the absorption caused emission (ACE). Moreover, the theoretical study is performed to support the sensing mechanism. The control titration of 1Zn suggest that the free –NH2 group of linker in 1Zn is involved in supramolecular interaction (hydrogen bonding) with the carboxylic group present on biomarker results the facile occurrence of electron transfer and ACE. Consequently, the luminescence “turn-on” effect of 1Zn for hyperprolinemia biomarker is observed.

Small-size and well-dispersed Fe nanoparticles embedded in carbon rods for efficient oxygen reduction reaction.

The preparation of ultra-small and well-dispersed metal nanoparticles (NPs) is of great importance for promoting oxygen reduction. Here, a metal (Fe and Zn) NP (7 nm) based catalyst derived from a Zn-based metal-organic framework was obtained by a vapor adsorption strategy, demonstrating a high half-wave potential (0.868 V) and power density (196 mW cm-2).

1.42-fold enhancement of formate selectivity by linker conversion on the Zn-based metal organic framework catalyst

Electro-reduction of carbon dioxide (ERCO2) is considered an effective method to alleviate the greenhouse effect and produce value-added chemicals. Achieving the dominant selectivity of Zn-based catalysts for formate remains a challenge. In this article, the ZnIn-E12 catalyst is successfully prepared by solvent assisted ligand exchange (SALE) method to convert organic ligands, achieving a Faradaic efficiency of 72.28% for formate at −1.26 V vs. RHE (VRHE), which is 1.42 times higher than the original catalyst. Evidence shows that the successful conversion of organic ligands can transform the catalyst from the original large size polyhedron to cross-linked network of particles with a diameter of about 30 nm. The increased specific surface area can expose more active sites and facilitate the electrocatalytic conversion of CO2 to formate. This work is expected to provide inspiration for the regulation of formate selectivity and catalyst size in Zn-based catalysts.

Carboxymethyl cellulose/Zn-based metal organic frameworks membranes for pervaporation-assisted esterification reactor

Pervaporation membrane reactors attract much attention as a promising system, in which separation and reaction are carried out simultaneously to overcome the thermodynamic equilibrium limitation and to increase the conversion by removing one or several synthesized products. For this, in this study supported carboxymethyl cellulose (CMC) membranes modified with Zn-based metal organic frameworks (Zn(SEB), Zn(BIM), Zn(BDC)Si) were developed. Transport properties of obtained membranes were evaluated in pervaporation separation of quaternary mixtures (acetic acid (AcOH), ethanol (EtOH), ethyl acetate (EtAc), water) with various compositions. CMC/Zn(BIM) membranes, possessed optimal transport characteristics, were tested in hybrid process “reaction + pervaporation” using batch pervaporation membrane reactor and compared with data obtained in batch reactor without membrane. The changes of structure and physicochemical properties of developed membranes were studied by spectroscopic, microscopic methods, thermogravimetric analysis and measurements of contact angles. To confirm findings obtained, theoretical consideration by computational methods for the CMC/Zn(BIM) membrane was carried out. It was shown that the application of optimal CMC/Zn(BIM)(10 wt%) membrane in pervaporation-assisted esterification reactor led to the formation of more than 5 times larger amount of EtAc in the reactor with decreased AcOH conversion compared to batch reactor without membrane in the separation of esterification reaction AcOH and EtOH (1/1 M) with 5 wt% Amberlyst 15 catalyst at 60 °C.

PH/cellulase dual environmentally responsive nano-metal organic frameworks for targeted delivery of pesticides and improved biosafety

Environmentally responsive pesticide nanocarriers can respond to the metabolites of pathogenic fungi as well as the soil microenvironment to achieve intelligent release of pesticides. In this work, a smart pH and cellulase dual environmentally responsive pesticide delivery system (Tebu@ZnMOFs@CMC) was constructed by combining carboxymethyl cellulose (CMC) and Zn-based metal–organic frameworks (ZnMOFs), which are loaded with tebuconazole (Tebu). Physicochemical characterization indicates the successful preparation of Tebu@ZnMOFs@CMC nanoparticles. The Tebu loading capacity was approximately 18.26%. Release simulations showed a higher cumulative release of Tebu under acidic and cellulase-promoted conditions. The surface coverage of carboxymethyl cellulose could effectively improve its spread on wheat and rice leaves. Compared with tebuconazole suspension concentrate (Tebu@SC) and tebuconazole technical, Tebu@ZnMOFs@CMC nanoparticles showed higher antifungal activity. It also had lower acute toxicity to zebrafish, Daphnia magna and earthworms, and no significant effect on wheat and rice. Thus, the dual environmentally responsive Tebu@ZnMOFs@CMC nanoparticles have great potential for achieving on-demand and targeted pesticide delivery.

Eu-doped ZIF-8 as a ratiometric fluorescence-scattering probe for the anthrax biomarker in food samples based on competitive coordination

Bacillus anthracis spores can cause contagious anthrax, so it is significant for the public safety to detect its biomarker dipicolinic acid (DPA). Ratiometric fluorescent probes for DPA have attracted great interest because of the self-calibration effect, but they suffer from the complicated construction of dual-emitting materials. With combining fluorescence and second-order scattering (SOS), Eu-doped Zn-based metal–organic framework (ZIF-8) was here designed as a ratiometric probe for DPA, avoiding the completed construction of dual-emitting materials. Eu-doped ZIF-8 exhibited no fluorescence but possessed strong SOS ascribed to the nanostructure. However, the competitive coordination of DPA not only triggered the antenna effect of Eu3+ but also caused the decomposition of Eu-doped ZIF-8. As a consequence, the fluorescence enhancement and the SOS weakness were observed upon the addition of DPA to Eu-doped ZIF-8. And thus, a ratiometric probe for DPA was constructed based on Eu-doped ZIF-8 by integrating fluorescence with SOS. The probe as-constructed could quantify DPA in a wide range of 0.1–150 μM with a rapid response (1 min) and a low detection limit (31 nM). It also displayed excellent manifestation for the analysis of food samples with reasonable accuracy (recoveries, 90.0%-101.5%) and satisfactory precision (RSDs, 0.6%-5.7%), offering a reliable tool for the supervision of the public safety.

Zn-based Metal-Organic Frameworks Using Triptycene Hexacarboxylate Ligands: Synthesis, Structure, and Gas-Sorption Properties.

A series of metal-organic frameworks (MOFs) based on zinc ions and two triptycene ligands of different size were synthesized under solvothermal conditions. The structural analyses revealed that these are isostructural three-dimensional-network MOFs. The high porosity and thermal stability of these MOFs can be attributed to the highly rigid triptycene-based ligands. Their BET specific surface areas depend on the size of the triptycene ligands. In contrast to these surface-area data, the H2 and CO2 adsorption of these MOFs is larger for MOFs with small pores. Consequently, we introduced functional groups to the bridge-head position of the triptycene ligands and investigated their effect on the gas-sorption properties. The corresponding results unveiled the role of the functional groups in the specific CO2 binding via an induced interaction between adsorbates and the functional groups. Excellent H2 and CO-2 properties in these MOFs were achieved in the absence of open metal sites.

Symmetry-Mismatched SBU Transformation in MOFs: Postsynthetic Metal Exchange from Zn to Fe and Its Effects on Gas Adsorption and Dye Selectivity.

This research explores the alteration of metal-organic frameworks (MOFs) using a method called postsynthetic metal exchange. We focus on the shift from a Zn-based MOF containing a [Zn4O(COO)6] secondary building unit (SBU) of octahedral site symmetry (ANT-1(Zn)) to a Fe-based one with a [Fe3IIIO(COO)6]+ SBU of trigonal prismatic site symmetry (ANT-1(Fe)). The symmetry-mismatched SBU transformation cleverly maintains the MOF's overall structure by adjusting the conformation of the flexible 1,3,5-benzenetribenzoate linker to alleviate the framework strain. The process triggers a decrease in the framework volume and pore size alongside a change in the framework's charge. These alterations influence the MOF's ability to adsorb gas and dye. During the transformation, core-shell MOFs (ANT-1(Zn@Fe)) are formed as intermediate products, demonstrating unique gas sorption traits and adjusted dye adsorption preferences due to the structural modifications at the core-shell interface. Heteronuclear clusters, located at the framework interfaces, enhance the heat of CO2 adsorption. Furthermore, they also influence the selectivity of the dye size. This research provides valuable insights into fabricating novel MOFs with unique properties by modifying the SBU of a MOF with flexible organic linkers from one site symmetry to another.

A sustainable approach for the removal of pharmaceutical contaminants from effluent using polyamide thin-film composite membranes integrated with Zn-based metal organic frameworks.

This study addresses the significant concern of pharmaceutical contaminants, including antipyretic and antibiotic drugs, in municipal and industrial wastewater, impacting both the environment and human health. We investigate incorporating zinc-based metal-organic framework (Zn-MOF) nanofillers into polyamide layers, developing thin-film composite (PA-TFC) nanofiltration membranes via interfacial polymerization to remove paracetamol, ibuprofen, and amoxicillin from simulated wastewater. Characterization confirms Zn-MOF's presence in the PA-TFC membrane, affecting structural topology, pore size, contact angles, and zeta potential. Zn-MOF nanofillers strongly adhere to the polyamide layer, influencing membrane surface chemistry and morphology. The newly developed MOF/PA-TFC nanofiltration membranes demonstrate a remarkable water flux of up to 35 LMH, showcasing superior removal efficiency for the three pharmaceutical contaminants when compared to PA-TFC membranes. Specifically, the rejection rates for paracetamol, ibuprofen, and amoxicillin are notably high at 93%, 98%, and 99%, respectively. Consequently, this study establishes MOF/PA-TFC nanofiltration membranes as a highly efficient solution for removing emerging pharmaceutical contaminants from environmental water, promoting sustainability and safeguarding water resources.

Facile synthesis of MOF-derived N doped ZnO/C nanoparticles and its adsorption activity toward dye removal

Metal–organic framework (MOF)-derived materials have gained an increasing interest and showed potential adsorption features in numerous applications. Significant attempts have been performed to boost the structure, functionality, surface area and porosity in addition to adsorption performance of MOF-derived carbon nanoparticles. Here, nitrogen-doped ZnO/carbon nanoparticles were synthesized by directly pyrolysis of Zn based metal organic framework (ZIF-8) in a nitrogen atmosphere at two different temperatures (600 and 800 °C), followed by chemical impregnation with ZnCl2 solution with ratio (10:1) wt/wt, and thermal activation at 500 °C for 1 h. SEM, TEM, XPS, nitrogen adsorption–desorption method, and TGA characterization techniques were employed to investigate the morphology and structure characteristics. Then, thorough analysis of N doped ZnO/C-(600 and 800), adsorption capacity to remove Remazol brilliant blue reactive (RBBR) dye from aqueous phase was conducted. At room temperature, the porous N doped ZnO/C with high surface area attained a maximum adsorption capacity about 49.3 mg/g and demonstrated a strong adsorption capacity toward RBBR dye. The insights of kinetic, thermodynamic and adsorption isotherm studies of the as-demonstrated samples open up more discussion for MOFs-derived carbon adsorbents for wastewater treatment.

Zn-based metal–organic framework with intramolecular hydrogen bond for the electroreduction of CO2 to formate

Zn-based metal–organic framework with intramolecular hydrogen bond for the electroreduction of CO2 to formate

FeCo alloy modified and carbon nanotube linked hollow carbon nanocages as efficient sulfur hosts for Li-S batteries

Although lithium-sulfur batteries have a high theoretical energy density, the lithium polysulfide (Li2Sn, n = 4 ∼ 8) shuttle effect and slow electrochemical reaction kinetics always arouse the poor rate performance, fast capacity decay and low Coulombic efficiency. Therefore, efficiently adsorption and timely catalytic conversion of Li2Sn by sulfur host is critical to overcome the above challenges of lithium sulfur batteries. In this work, an FeCo alloy modified and carbon nanotube linked hollow carbon nanocages host (CoFe-CHC-X) is constructed by in situ transformation of Fe and Co elements doped Zn-based metal-organic frameworks and melamine. Moreover, the catalytic properties of the CoFe-CHC-X with different Fe and Co ratios are investigated. The results reveal that both small and excessive amounts of Co metal nanoparticles in CoFe-CHC-1 and CoFe-CHC-2 composites are not conducive to the adsorption and conversion of Li2Sn. In contrast, the separated and uniformly dispersed FeCo alloy nanoparticles in CoFe-CHC-3 composite not only can effectively adsorb Li2Sn, but also reduce it conversion reaction energy barriers, accelerate conversion kinetics and inhibit shuttle effects. Meanwhile, the hollow carbon nanocages linked by carbon nanotube can facilitate the transport of electrons on the cathode and physical adsorption Li2Sn. Benefiting from these synergistic modulations, the Li-S batteries assembled by S@FeCo-CHC-3 cathode can stably cycle for 700 cycles at 1.0 C. During cycle, the Coulombic efficiency is maintained at about 98%, and the capacity decay is as low as 0.052% per cycle.