Stable MOF Research Articles

Potential-resolved real-time ultrasensitive sensing of bisphenol compounds based on ionic liquid coupled Zr-MOF@GO nanosensor

Bisphenol compounds, including BPA and BPS, are significant pollutants found in the environment, food, and daily necessities. They pose various adverse effects, including estrogenic, immunotoxic, metabolic, and reproductive toxicity, which severely threaten human health and ecological safety. Achieving simultaneous rapid detection of BPA and BPS is still very challenging due to their similar structures and co-existence in actual samples at ultratrace level. This study addresses the problem of developing an effective method for the rapid detection of BPA and BPS simultaneously. A new electrochemical nanosensor based on ionic liquid (IL) coupled Zr-MOF@GO was developed for ultrasensitive real-time detection of BPA and BPS. The Zr-MOF@GO/IL nanocomposite features a custom-built structure with an ordered framework, abundant pores, and highly coupled interfaces. The experimental findings demonstrate that the introduction of IL enhances the conductivity and dispersibility of the nanocomposite, improves the absorption capability for target bisphenols, and significantly improves the detection limit and linear range of the Zr-MOF@GO based electrochemical sensor. The sensor demonstrated wide linear ranges with detection limits of 5.5 nmol/L for BPA and 7.1 nmol/L for BPS (S/N = 3), respectively. Comparative studies revealed that the detection limits of the Zr-MOF@GO/IL-based sensor improved by an order of magnitude compared to the Zr-MOF@GO-based sensor. Additionally, the sensor exhibited superior analytical performance regarding reproducibility, stability, and selectivity. This study investigated the capability and synergy of IL coupled high-valent stable transition metal ZrIV-based MOFs in electrochemical sensing for the first time. This development sets a new benchmark in non-enzymatic electrochemical sensing, establishing the Zr-MOF@GO/IL-based sensor as a promising platform for the individual or simultaneous rapid detection of bisphenols in actual samples.

Visible-light-assisted peroxymonosulfate activation using MIL-88A(Fe)/BiOI heterojunction composite to drive charge transport for eliminating acid red 18

A novel rod-shaped MIL-88A(Fe)/BiOI heterojunction composite is fabricated by an in-suit chemical deposition method for visible-light-assisted peroxymonosulfate activation to eliminate AR18 (acid red 18). A series of x%MIL-88A(Fe)/BiOI are obtained according to the mass ratio of MIL-88A(Fe) to BiOI. Among them, 30 %MIL-88A(Fe)/BiOI could remove 97.79 % AR18 within 40 minutes. The reaction parameters on this process are investigated, such as PMS concentration, catalyst dosage, initial pH and dye concentration. The optimal conditions are determined to be [catalyst]= 1 g·L−1, [PMS]=1 mM, pH=7.02. The scavenging experiments and EPR analysis manifest that 1O2 is the main active species for AR18 degradation. In accordance with the band structure, active species, XPS, PL, EIS and photocurrent response, the Z-scheme electron transfer path of the composite catalyst is proved under 500 W (λ > 420 nm) Xenon lamp irradiation. In the end, the stability and universality of the composite catalyst in practical application are evaluated by three cyclic tests and inorganic anion experiments. This work provides valuable guidance for synthesizing efficient and stable MOF based heterojunction photocatalysts.

Glycyrrhizic acid and glycyrrhetinic acid loaded cyclodextrin MOFs with enhanced antibacterial and anti-inflammatory effects for accelerating diabetic wound healing

A water stable cyclodextrin MOF (Cu-SD) was synthesized with γ-cyclodextrin derivative as organic ligand and Cu2+ as metal center to co-crystallizely load glycyrrhizic acid (GL) and glycyrrhetinic acid (GA). Cu-SD has a high drug loading capacity for GL (499.91 μg/mg) and GA (112.37 μg/mg), and the drug-loaded materials had a controlled release in different meadiums. In addition, Cu-SD and its drug loaded materials demonstrated better inhibiting α-glucosidase activity than the control drug acarbose. Furthermore, Cu-SD presented excellent antibacterial activity, and the antibacterial activity was significantly enhanced after GA and GL being encapsulated by Cu-SD. Moreover, both free and drug-loaded materials had good anti-inflammatory activities, and the anti-inflammatory effects of GL@Cu-SD and GA@Cu-SD were superior to those of their corresponding free drugs. Cu-SD, GL@Cu-SD and GA@Cu-SD demonstrated good biocompatibility and were applied to treat the wounds of diabetic rats. The experimental results showed that GL@Cu-SD and GA@Cu-SD had good promoting effects on the recovery of chronic diabetic wounds by suppressing wound inflammation.

CoCorrole-Functionalized PCN-222 for Carbon Monoxide Selective Adsorption.

The high risk of CO poisoning justifies the need for indoor air quality control and warning systems based on the detection of low concentrations (ppm-ppb) of CO. Cobalt corrole complexes selectively bind CO vs. O2, CO2, N2, opening new fields of applications. By combining the CO chemisorption properties of cobalt corroles with the known sorption capacity of MOFs, we hope to obtain high performance sensing materials for CO detection. In addition, the exposed metal sites of MOFs lead to CO2 physisorption, allowing the co-detection of CO and CO2. In this work, PCN-222, a stable Zr-based MOF made from Ni(TCPP) with natural vacancies, has been used as a porous matrix for the grafting of electron-poor metallocorroles. The materials were characterized by powder XRD, SEM and optical microscopy, BET analyses and gas adsorption measurements at 298 K. No degradation of the crystalline structure of PCN-222 was observed. At 1 atm, the adsorbed CO(g) volumes measured for the best materials were 12.15 cm3 g-1 and 14.01 cm3 g-1 for CoCorr2@PCN-222 and CoCorr3@PCN-222 respectively, and both materials exhibited high CO chemisorption and selectivity against O2, N2, and CO2 at low pressure due to the highest energy of the chemisorption process vs physisorption.

Preparation of UiO-66 MOF-Bonded Porous-Layer Open-Tubular Columns Using an In Situ Growth Approach for Gas Chromatography.

The thermally stable zirconium-based MOF, UiO-66, was employed for the preparation of bonded porous-layer open-tubular (PLOT) GC columns. The synthesis included the in situ growth of the UiO-66 film on the inner wall of the capillary through a one-step solvothermal procedure. SEM-EDX analysis revealed the formation of a thin, continuous, uniform, and compact layer of UiO-66 polycrystals on the functionalized inner wall of the column. The average polarity (ΔIav = 700) and the McReynolds constants reflected the polar nature of the UiO-66 stationary phase. Several mixtures of small organic compounds and real samples were used to evaluate the separation performance of the fabricated columns. Linear alkanes from n-pentane to n-decane were baseline separated within 1.35 min. Also, a series of six n-alkylbenzenes (C3-C8) were separated within 3 min with a minimum resolution of 3.09, whereas monohalobenzene mixtures were separated at 220 °C within 14s. UiO-66 PLOT columns are ideally suited for the isothermal separation of chlorobenzene structural isomers at 210 °C within 45 s with Rs ≥ 1.37. The prepared column featured outstanding thermal stability (up to 450 °C) without any observed bleeding or significant impact on its performance. This feature enabled the analysis of various petroleum-based samples.

Gas adsorption and framework flexibility of CALF-20 explored via experiments and simulations

In 2021, Svante, in collaboration with BASF, reported successful scale up of CALF-20 production, a stable MOF with high capacity for post-combustion CO2 capture which exhibits remarkable stability towards water. CALF-20’s success story in the MOF commercialisation space provides new thinking about appropriate structural and adsorptive metrics important for CO2 capture. Here, we combine atomistic-level simulations with experiments to study adsorptive properties of CALF-20 and shed light on its flexible crystal structure. We compare measured and predicted CO2 and water adsorption isotherms and explain the role of water-framework interactions and hydrogen bonding networks in CALF-20’s hydrophobic behaviour. Furthermore, regular and enhanced sampling molecular dynamics simulations are performed with both density-functional theory (DFT) and machine learning potentials (MLPs) trained to DFT energies and forces. From these simulations, the effects of adsorption-induced flexibility in CALF-20 are uncovered. We envisage this work would encourage development of other MOF materials useful for CO2 capture applications in humid conditions.

Influence of activated protons and acid–base pairs on proton conduction in imino-functionalized MOF-based hybrid membranes

The rich activated protons and effective proton-conducting paths are of importance to improve conductivities of conductors. Herein, a series of Brönsted acids as proton carrier and proton transfer sites is introduced into the highly stable MOF, contributing to create plentiful hydrogen bonds within frameworks. Consequently, the trifluoromethanesulfonic acid-embedded JUC-1000 ([Cu24(BDPO)12(H2O)12]) displays the relatively highest conductivity of 7.04 × 10−4 S cm−1 under ∼98% RH and 328 K, ∼16 times that of JUC-1000 (4.47 × 10−5 S cm−1). When TMSA@JUC-1000 (TMSA = CF3SO3H) blended with chitosan (CS), the proton conductivity of TMSA@JUC-1000/CS-15 is the highest at ∼76% RH and 328 K (1.01×10−2 S cm−1), which is six times higher than that of JUC-1000/CS (1.85×10−3 S cm−1). The CS contains abundant –NH2 and –OH groups as proton jumping sites, which would activate the –NH– or –OH bonds of JUC-1000 and the acidic groups in Brönsted acids. These would result in an increased content of activated protons and effective formation of H-bonding nets by acid-base interactions. The findings provide valuable insights into the potential application of MOFs materials in energy devices.

A Highly Stable Microporous Calcium-Based MOF for C2H2/CO2 Separation with Low Regenerative Energy.

Most of the porous materials used for acetylene/carbon dioxide separation have the problems of poor stability and high energy requirements for regeneration, which significantly hinder their practical application in industries. Here, we report a novel calcium-based metal-organic framework (NKM-123) with excellent chemical stability against water, acids, and bases. Additionally, it has exceptional thermal stability, retaining its structural integrity at temperatures up to 300 °C. This material exhibits promising potential for separating C2H2 and CO2 gases. Furthermore, it demonstrates an adsorption heat of 29.3 kJ mol-1 for C2H2, which is lower than that observed in the majority of MOFs used for C2H2/CO2 separations. The preferential adsorption of C2H2 over that of CO2 is confirmed by dispersion-corrected density functional theory (DFT-D) calculations. In addition, the potential of industrial feasibility of NKM-123 for C2H2/CO2 separation is confirmed by transient breakthrough tests. The robust cycle performance and structural stability of NKM-123 during multiple breakthrough tests show great potential in the industrial separation of light hydrocarbons.

Highly Stable 72-Nuclearity Nanocages for Efficient Synthesis of Aryl Nitriles via Ni/Cu Synergistic Catalysis.

Seeking noble-metal-free catalysts for efficient synthesis of aryl nitriles under mild conditions poses a significant challenge due to the use of hypertoxic cyanides or high-pressure/temperature NH3/O2 in conventional synthesis processes. Herein, we developed a novel framework 1 assembled by [Ni72] nanocages with excellent solvents/pH stability. To investigate the structure-activity relationship of catalytic performance, several isostructural MOFs with different molar ratios of Ni/Cu by doping Cu2+ into framework 1 (Ni0.59Cu0.41 (2), Ni0.81Cu0.19 (3), Ni0.88Cu0.12 (4), and Ni0.92Cu0.08 (5)) were prepared. Catalytic studies revealed that catalyst 3 exhibited remarkable performance in the synthesis of aryl nitriles, utilizing a formamide alternative to hypertoxic NaCN/KCN. Notably, catalyst 3 achieved an excellent TOF value of 9.8 h-1. Furthermore, catalyst 3 demonstrated its applicability in a gram-scale experiment and maintained its catalytic performance even after six recycling cycles, owing to its high stability resulting from significant electrostatic and orbital interactions between the Ni center and ligands as well as a large SOMO-LUMO energy gap supported by DFT calculations. Control experiments and DFT calculations further revealed that the excellent catalytic performance of catalyst 3 originated from the synergistic effect of Ni/Cu. Importantly, this work not only provides a highly feasible method to construct highly stable MOFs containing multinuclear nanocages with exceptional catalytic performance but also represents the first example of a heterogeneous catalyst for the synthesis of aryl nitriles using formamide as the cyanide source.

Amino-functionalized rare earth hexanuclear cluster based MOFs for CO2/CH4 separation

Climate pollution and global warming caused by greenhouse gases have become one of our toughest environmental challenges. CO2 capture and separation from natural gas can effectively reduce CO2 emissions and improve energy efficiency, accordingly, it is a serious challenge faced by industrial separation and scientific research to effectively reduce the carbon dioxide concentration in natural gas pipeline transportation and achieve the acquisition of high-purity methane (>99.5 %). In this study, three stable hexanuclear microporous rare earth cluster-based MOFs (Sm-BDC-NH2, Er-BDC-NH2, Y-BDC-NH2) were successfully synthesized. The selectivity of CO2/CH4 was improved by the introduction of amino groups to achieve better CO2/CH4 separation performance, which was proved by dynamic penetration experiments.

Biogas upgrading using shaped MOF MIL-160(Al) by pressure swing adsorption process: Experimental and dynamic modelling assessment

Biogas has been introduced as a sustainable source of energy, which is considered as a promising alternative for conventional fossil fuels. Indeed, biogas requires to be upgraded from the impurities, specifically, carbon dioxide to be commercially utilized. In this study, the potential of shaped form MIL-160(Al) as a water stable Al dicarboxylate microporous MOF has been assessed concerning the biogas upgrading application. To this end, firstly, the dynamic fixed-bed adsorption of carbon dioxide and methane was investigated at 313 K and 4.0 bar. The measured breakthrough outcomes were simulated with a developed mathematical model, which the results confirmed an acceptable potential of model predictions. Afterwards, a pressure swing adsorption (PSA) process with 5-steps was designed relying on dynamic equilibrium results, and experimentally validated by a lab-scale PSA set-up for a 50:50 CO2/CH4 mixture. Finally, an industrial PSA process was designed to have a precise knowledge on the potential of MIL-160(Al) for biogas upgrading for large scale applications. The results demonstrated the purity and recovery of methane around 99 % and 63 %, respectively, which indicated the appealing capacity of this adsorbent for such a purpose.

Synergistic catalysis of Ru0-Ru3+ in MOF supported ultrafine Ru nanoparticles catalyst promotes ethyl levulinate to γ-valerolactone

Synthesis of bifunctional catalysts is very important for the hydrogenation of biomass to advanced biofuels, but its efficient regulation is difficult. In this work, a tunable bifunctional Ru/LaQS catalyst with Lewis acid and metal hydrogenation sites was prepared by stable MOFs (LaQS) supported ultrafine Ru nanoparticles (NPs). When the optimal Ru2/LaQS catalyst catalyzed bio-based ethyl levulinate (EL) to γ-valerolactone (GVL), the EL conversion and GVL selectivity reached 99.9% under mild conditions of 100 °C. The excellent catalytic performance is mainly attributed to the synergistic effect of Ru0-Ru3+ on ultrafine Ru NPs with only 1.60 nm generated by metal-support interaction, which is proved by experimental characterization and theoretical calculation. Moreover, the electron density of hydrogenation active site Ru0 and the content of acidic site Ru3+ can be modulated by Ru loading. Among them, the activation of H2 was promoted by the high electron density of Ru0 generated through metal-support electronic interactions. The enhanced medium-strong acidic site Ru3+ not only improved the activation of EL, but also promoted the intramolecular dealcoholization of the intermediate to GVL. The synergistic catalytic mechanism of Ru0-Ru3+ on ultrafine Ru NPs was speculated. The excellent stability was mainly attributed to the metal-support interaction stabilizing the ultrafine Ru NPs, which prevents the agglomeration and loss of Ru NPs during cycling. This work provides an in-depth understanding of the bifunctional catalytic mechanism, which is of guiding significance for the design and preparation of MOFs-based catalysts for biomass hydrogenation.

High C2H6/C2H4 selectivity via incorporation of dense methyl groups into a stable Zr-based MOF with cavity-like pores

The development of efficient adsorbents for C2H6/C2H4 separation is an important and challenging issue for the economical production of high-purity ethylene, a valuable precursor for the petrochemical industry. We developed an efficient adsorbent for C2H6/C2H4 separation by incorporating highly dense methyl groups into a highly stable UiO-66 framework with “cavity-like” pores. Remarkably, UiO-66-2Me exhibited large C2H6 uptake at 1 bar (2.15 mmol/g) and significantly high C2H6/C2H4 IAST selectivity (2.93), which is one of the highest values reported. From a combined experiments and computational study, we verified that the observed high selectivity was originated from the specific interaction between C2H6 and multiple methyl groups in the cavity-like pores. Moreover, UiO-66-2Me showed high C2H6/C2H4 selectivity (2.05) even under the dynamic mixture flow condition, easy regeneration and good hydrothermal and thermal stabilities. These results suggest that incorporating highly dense methyl groups into a stable MOF with cavity-like pores is a promising method for developing an efficient adsorbent for C2H6/C2H4 separation.

A novel multi-carboxyl functionalized MOF platform for effective photodynamic therapy with hypoxia modulation based on prominent self-oxygen generation

We for the first time, using a multicarboxyl modification strategy, integrated high density Fe-based catalytic centers and the clinically available ICG molecule into the same stable MOFs and obtained a novel self-oxygen generation enhanced PDT platform.

Construction of a series of pH stable Ca-based MOFs, their CO2 adsorption and catalytic activity.

In this study, three different solvent systems have been employed to investigate the effect of reaction parameters on the synthesis of four alkaline earth metal-based MOFs namely [Ca(0.5 1,4-phenyl diacetic acid)2(H2O)DMF]∞ (Ca-MOF-1), [Ca(1,4-naphthalene dicarboxylate)DMF]∞ (Ca-MOF-2), [Ca2(0.5 1,2,4,5-benzene tetracarboxylate)2(H2O)3DMF]∞ (Ca-MOF-3) and [Ca2(2,6-naphthalene dicarboxylate)2(H2O)6]∞ (Ca-MOF-4). The crystal structures of these four MOFs have been resolved through single crystal X-ray analysis and the bulk phase purity of these MOFs was assessed using PXRD and FT-IR analysis. To check the stability of these MOFs, thermogravimetric analysis (TGA) was carried out. To analyze the robustness of these MOFs, the PXRD of the samples was also collected at different pH levels. These MOFs were further explored as Lewis acid catalysts for the alcoholysis of epoxides and the activity of these catalysts depend on the open metal sites present in the MOFs. The catalytic activity follows the order: Ca-MOF-2 > Ca-MOF-4 > Ca-MOF-1 > Ca-MOF-3. The activity was also checked with various epoxide substrates using Ca-MOF-2. Density functional theory (DFT) calculations also support this trend with the help of the thermodynamic feasibility of epoxide binding, considering model MOF structures. The weak interaction between the epoxide oxygen and the metal centre of the most stable MOF structure has also been clarified by computational studies.

Significant adsorption enhancements driven by pore microenvironment tuning for efficient C2H2/C2H4 separation in a chemically stable Ni7-cluster-based framework

This study presents a stable Ni7-cluster MOF with enhanced adsorption through pore microenvironment tuning. Two types of guest-free frameworks achieve C2H2/C2H4 separation, providing deep insights into separation mechanisms.

2D pyrene-based metal–organic framework nanobelts as efficient photocatalysts for the coupling of thiols into disulfides

2D pyrene-based metal–organic framework nanobelts for the photocatalytic coupling of thiols into disulfides.

Synthesis of diverse stable MOFs and their electro catalytic capabilities towards desulfurization, water splitting and various nitrophenol reduction reactions

Metal–organic frameworks are a novel class of crystalline porous materials with enormous application potential, consisting of metal nodes and organic linkers.

New insight into the co-removal of arsenic and cadmium from wastewater by using thiol-functionalized UiO-66: A mechanistic study and real water test

Industrial wastewater is normally a complex matrix, and few reported MOFs have considered the co-removal of anion and cation contaminants from wastewater. In this study, we synthesized a highly stable thiol-functionalized MOF (UiO-66-SH) to achieve the coadsorption of As(V) and Cd(II) in an aqueous solution. The morphology, functional groups and thermal properties of UiO-66-SH were examined. The prepared UiO-66-SH possessed an octahedral structure (size: 0.8–2 μm) with a large surface area (224 m2/g). TEM-EDX mapping showed a uniform distribution of S and Zr throughout UiO-66-SH. The FT-IR spectra showed peaks for -SH at 2566 cm-1, indicating that -SH was successfully incorporated into UiO-66. Adsorption batch experiments showed that both As(V) and Cd(II) were rapidly taken up by UiO-66-SH in the first 6 h, and the removal rates were over 70% and 88%, respectively, after 24 h. The maximum As(V) and Cd(II) adsorption capacities were 52.31 and 77.42 mg/g. The optimum pH values for As(V) and Cd(II) adsorption were 3 and 5, respectively. Except for Pb(II) and phosphate, anions, cations, and humic acid had almost no effect on As(V) and Cd(II) co-removal by UiO-66-SH. Spectral analysis indicated that surface hydroxyl groups (Zr-OH) and -SH groups played vital roles in As(V) and Cd(II) adsorption by participating in inner-sphere coordination interactions. A real water test showed that a very small amount of UiO-66-SH could decrease the concentration to below the emission standard within 6 h. Our study demonstrated that UiO-66-SH is a promising adsorbent for treating As- and Cd-cocontaminated mining wastewater, ensuring the environmental safety of wastewater emission.

UiO-66 metal organic framework as stable platform for non-linear optical applications

We report on the experimental study the non-linear optical properties of UiO-66 metal-organic framework with high thermal and chemical stability. We demonstrate the coherent conversion of high-intensity incoming radiation into the third harmonics ranging from 450 to 600 nm. Moreover, eclipse z - scan of single UiO-66 microcrystals made it possible to determine the saturable absorption coefficient (βeff = −1.415·10-2 cm/GW at 515 nm and −3.865·10-1 cm/GW at 1030 nm), thereby, bringing UiO-66 to the list of nonlinear and stable MOFs for real-life photonic applications.