Enhanced transformation of CO2 over microporous Ce-doped Zr metal–organic frameworks

Metal–organic frameworks (MOF) have been studied extensively for the adsorption and catalytic conversion of CO₂. However, previous studies mainly focused on the adsorption capabilities of partially or totally Ce substituted UiO-66, there are few studies focusing on transformation of the structure and catalytic activity of these materials. In this work, a series of Zr/Ce-based MOFs with UiO-66 architecture catalysts were prepared for the conversion of CO₂ into value-added dimethyl carbonate (DMC). Owing to the different addition order of the two metals, significantly varied shapes and sizes were observed. Accordingly, the catalytic activity is greatly varied by adding a second metal. The different catalytic activities may arise from the different acid–base properties after Ce doping as well as the morphology and shape changes. Besides, the formation of terminal methoxy (t-OCH₃) was found to be the rate limiting step. Finally, the reaction mechanism of CO₂ transformation in the presence of a dehydrating agent was proposed.

Different doping order of Ce/Zr have a significant effect on the morphologies, acid properties as well as on the activities for CO₂ conversion of the MOF materials.     

Synthesis and adsorption performance of La@ZIF-8 composite metal–organic frameworks

In this study, ZIF-8 with a rhombic dodecahedron structure was prepared by a hydrothermal method. Then La(OH)₃, was successfully loaded onto the ZIF-8 by an immersion deposition method, to form a lanthanide-based metal–organic framework (La@ZIF-8) composites. The structure and properties of La@ZIF-8 were verified by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and zeta potential measurements. The optimum process conditions are discussed within the materials and methods. The effects of initial phosphorus concentration, dosage, pH and contact reaction time on the phosphorus removal performance of the nanomaterial were investigated. The results indicated that La@ZIF-8 exhibited an excellent adsorption capacity (147.63 mg g⁻¹) and its phosphorus removal efficiency could reach as high as 99.7%. Experimental data were interpreted using different adsorption kinetic and isotherm models. The kinetic behavior conformed to the pseudo-second-order kinetic model, which indicated the chemisorption of phosphorus by La@ZIF-8. The adsorption behavior of phosphorus by La@ZIF-8 fitted well to the Langmuir isotherm model, suggesting a monolayer chemical adsorption process. The majority of the adsorbed phosphate could be desorbed by NaOH (2 mol L⁻¹), and the removal efficiency of the recycled La@ZIF-8 reached 90%, even after the fifth cycle. The obtained results demonstrate the great application potential of the prepared La@ZIF-8 as a fascinating adsorbent for the removal of phosphate.

In this study, La(OH)₃ was successfully loaded on ZIF-8 by immersion deposition method, to form lanthanide-based metal–organic frameworks (La@ZIF-8) composites.     

Modelling drug adsorption in metal–organic frameworks: the role of solvent

Solvent plays a key role in biological functions, catalysis, and drug delivery. Metal–organic frameworks (MOFs) due to their tunable functionalities, porosities and surface areas have been recently used as drug delivery vehicles. To investigate the effect of solvent on drug adsorption in MOFs, we have performed integrated computational and experimental studies in selected biocompatible MOFs, specifically, UiO-AZB, HKUST-1 (or CuBTC) and NH₂-MIL-53(Al). The adsorption of three drugs, namely, 5-fluorouracil (5-FU), ibuprofen (IBU), and hydroxyurea (HU) were performed in the presence and absence of the ethanol. Our computational predictions, at 1 atmospheric pressure, showed a reasonable agreement with experimental studies performed in the presence of ethanol. We find that in the presence of ethanol the drug molecules were adsorbed at the interface of solvent and MOFs. Moreover, the computationally calculated adsorption isotherms suggested that the drug adsorption was driven by electrostatic interactions at lower pressures (<10⁻⁴ Pa). Our computational predictions in the absence of ethanol were higher compared to those in the presence of ethanol. The MOF–adsorbate interaction (U_HA) energy decreased with decrease in the size of a drug molecule in all three MOFs at all simulated pressures. At high pressure the interaction energy increases with increase in the MOFs pore size as the number of molecules adsorbed increases. Thus, our research shows the important role played by solvent in drug adsorption and suggests that it is critical to consider solvent while performing computational studies.

Solvent plays a key role in drug loading in metal–organic frameworks.     

Screening of metal–organic frameworks for water adsorption heat transformation using structure–property relationships

It is of great importance to correlate the water adsorption performance of MOFs to their physicochemical features in order to design and prepare MOFs for applications in adsorption heat transformation. In this work, both data analysis from existing studies and Grand Canonical Monte Carlo molecular simulation investigations were carried out. The results indicated that the highest water adsorption capacity was determined by the pore volume of MOF adsorbents, while there was a linear correlation interrelationship between isosteric heats of adsorption and the water adsorption performance at a low relative pressure. More detailed analysis showed that the charge distribution framework and pore size of MOFs contributed together to the hydrophilicity. Electrostatic interaction between water molecules and the framework atoms played a key role at low relative water pressure. A quantitative structure–property relationship model that can correlate the hydrophilicity of MOFs to their pore size and atomic partial charge was established. Along with some qualitative considerations, the screening methodology is proposed and is used to screen proper MOFs in the CoRE database. Seven MOFs were detected, and four of them were synthesized to validate the screening principle. The results indicated that these four MOFs possessed outstanding water adsorption performance and could be considered as promising candidates in applications for adsorption heating and cooling.

Quantitative structure–property relationship models that correlate the water adsorption performance of MOFs to their physicochemical features have been established.     

Synthesis of heterometallic metal–organic frameworks and their performance as electrocatalyst for CO2 reduction

Herein we report the solventless synthesis and doping of the benchmark HKUST-1(Cu) as a facile route to afford heterometallic metal–organic frameworks (MOFs) having proficient behavior as electrocatalytic materials in the reduction of carbon dioxide. Zn(ii), Ru(iii) and Pd(ii) were selected as doping metals (M_D) with the aim of partially replacing the Cu(ii) atoms of the pristine structure to afford HKUST-1(Cu,M_D) type materials. Apart from the high yield and good crystallinity of the obtained materials, the extremely high reagent concentration that the reaction conditions imply makes it feasible to control dopant loading in all cases. Prepared samples were processed as electrodes and assembled in a continuous flow filter-press electrochemical cell. Faraday efficiency to methanol and ethanol at Ru(iii)-based electrodes resulted in activity as high as 47.2%, although the activity of the material decayed with time. The interplay of the dopant metal and copper(ii), and the long-term performance are also discussed.

The solventless synthesis of heterometallic metal–organic frameworks and their proficient behavior as electrocatalysts in the CO₂ reduction to alcohols is presented.     

Simultaneous adsorption of SO2 and CO2 in an Ni(bdc)(ted)0.5 metal–organic framework

The metal–organic framework Ni(bdc)(ted)_0.5 is a promising material for simultaneous capture of harmful gases such as SO₂ and CO₂. We found that SO₂ performs much better than CO₂ during adsorption, and the lack of physical insight was clarified through detailed analyses of the electronic structures obtained from density functional theory calculations. Our results showed that strong interactions of the d band of Ni atoms with the valence states (2n, 3n, and 4n) of SO₂ but almost not with those of CO₂ are the main reasons. Our finding is useful for the rational design of new metal–organic frameworks with suitable interactions for the simultaneous capture of not only SO₂ and CO₂ but also other gases.

SO₂ performs much better than CO₂ during co-adsorption due to the d-band of Ni atoms.     

A novel route to size-controlled MIL-53(Fe) metal–organic frameworks for combined chemodynamic therapy and chemotherapy for cancer

Metal–organic frameworks (MOFs), such as MIL-53(Fe), have considerable potential as drug carriers in cancer treatment due to their notable characteristics, including controllable particle sizes, high catalytic activity, biocompatibility and large porosity, and are widely used in a broad range of drugs. In this study, a new approach for the synthesis of MIL-53(Fe) nanocrystals with controlled sizes has been developed using a non-ionic surfactant PVP as the conditioning and stabilizing agent, respectively. During the nucleation of MIL-53(Fe), the PVP droplet, as a nano-reactor, controlled the growth of the crystal nucleus. The size and aspect ratio (length/width) of nanocrystals increased with an increase in PVP in the synthetic mixture. The MIL-53(Fe) nanocrystals showed a homogeneous morphology, with approximately 190 nm in length and 100 nm in width. MIL-53(Fe) not only was used to load the anticancer drug doxorubicin (DOX) but also generated hydroxyl radicals (˙OH) via a Fenton-like reaction for ROS-mediated/chemo-therapy of cancer cells. The approach was expected to synthesize numerous types of nano-size iron(iii)-based MOFs, such as MIL-53, 89, 88A, 88B and 101. The MIL-53(Fe) nanocrystals hold great promise as a candidate to improve the controlled release of drugs and treatment effect for cancer therapy.

In this study, we reported a new approach for the size-controlled synthesis of uniform iron(iii)-based MIL-53 nanocrystals using the non-ionic surfactant PVP. A combinational therapeutic approach was presented for drug delivery and ROS therapy.     

Removal of anthracene in water by MIL-88(Fe), NH2-MIL-88(Fe), and mixed-MIL-88(Fe) metal–organic frameworks

Three adsorbents based on the metal–organic frameworks (MOFs), viz.; MIL-88(Fe), NH₂-MIL-88(Fe), and mixed-MIL-88(Fe) were synthesized using a microwave-assisted solvothermal technique. The as-synthesized MOFs were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), field emission scanning microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). The MOFs were shown to possess highly crystalline and porous structures with specific surface areas of 1240, 941, and 1025 m² g⁻¹ and pore volumes of 0.7, 0.6 and 0.6 m³ g⁻¹ for MIL-88(Fe), NH₂-MIL-88(Fe) and mixed-MIL-88(Fe), respectively. Faster removal of a model polycyclic aromatic hydrocarbon, anthracene (ANT) within 25 minutes, was achieved when these MOFs were used as adsorbents in water. The removal efficiency was 98.3, 92.4 and 95.8% for MIL-88(Fe), NH₂-MIL-88(Fe) and mixed-MIL-88(Fe), respectively. The kinetics and isotherms of the process were best statistically described by pseudo-second-order and Langmuir models, respectively, while the thermodynamic studies revealed the exothermic and spontaneous nature of the process. Docking simulations were found to be consistent with the experimental results with MIL-88(Fe) showing the best binding capacity with the ANT molecule.

Three adsorbents based on the metal–organic frameworks (MOFs), viz.; MIL-88(Fe), NH₂-MIL-88(Fe), and mixed-MIL-88(Fe) were synthesized using a microwave-assisted solvothermal technique.     

Mesoporous Cu–Cu2O@TiO2 heterojunction photocatalysts derived from metal–organic frameworks

This study reveals a unique Cu–Cu₂O@TiO₂ heterojunction photocatalyst obtained with metal–organic framework as the precursor, which can be utilized in dye photodegradation under visible light irradiation. The composition, structure, morphology, porosity, optical properties and photocatalytic performance of the obtained catalysts were all investigated in detail. The Cu–Cu₂O@TiO₂ nanocomposite is composed of lamellar Cu–Cu₂O microspheres embedded by numerous TiO₂ nanoparticles. Methylene blue, methyl orange and 4-nitrophenol were used as model pollutants to evaluate the photocatalytic activity of the Cu–Cu₂O@TiO₂ nanocomposite for dye degradation under visible light irradiation. Nearly 95% decolourisation efficiency of Methylene blue was achieved by the Cu–Cu₂O@TiO₂ photocatalyst within 3 h, which is much higher than that of TiO₂ or Cu₂O catalysts. The excellent photocatalytic activity was primarily attributed to the unique MOF-based mesoporous structure, the enlarged photo-adsorption range and the efficient separation of the charge carriers in the Cu–Cu₂O@TiO₂ heterojunction.

Cu–Cu₂O@TiO₂ heterojunction photocatalyst derived from a metal–organic framework shows high photocatalytic activity for dye degradation under visible light irradiation.     

Recognition of trace organic pollutant and toxic metal ions via a tailored fluorescent metal–organic coordination polymer in water environment

A novel fluorescence material H₂Sr₂(bqdc)₃(phen)₂ (1) for trace recognition of organic pollutant and toxic metal ions is designed and prepared by two weak fluorescent ligands and Sr²⁺. The latter was selected although it played no role in the modulation process of luminescence and despite low-cost, alkaline earth, metal–organic coordination polymers lacking competitive functionality. The strong fluorescence of the fluorescence material was based on the propeller configuration of the metal–organic coordination polymer, which was characterized by X-ray single crystal diffraction showing that the N active sites inside the crystal channels can interact with external guests. Convenient fluorescence detection of 3-AT can be realized using an ultraviolet lamp and test strip and the determination of Cd²⁺ showed good reusability with a detection limit of 1 × 10⁻⁹ mol L⁻¹, which is lower than the standard stipulated by the Environmental Protection Agency. Detailed experiments results revealed that the material was a promising candidate for specifically recognizing amitrole and Cd²⁺ because of its selective fluorescence quenching and sensitive detection in water.

Complexes with strong fluorescence can conveniently detect the trace organic pollutant amitrole and repeatedly recognize toxic Cd²⁺with a low detection limit.     

A collection of forcefield precursors for metal–organic frameworks

A host of important performance properties for metal–organic frameworks (MOFs) and other complex materials can be calculated by modeling statistical ensembles. The principle challenge is to develop accurate and computationally efficient interaction models for these simulations. Two major approaches are (i) ab initio molecular dynamics in which the interaction model is provided by an exchange–correlation theory (e.g., DFT + dispersion functional) and (ii) molecular mechanics in which the interaction model is a parameterized classical force field. The first approach requires further development to improve computational speed. The second approach requires further development to automate accurate forcefield parameterization. Because of the extreme chemical diversity across thousands of MOF structures, this problem is still mostly unsolved today. For example, here we show structures in the 2014 CoRE MOF database contain more than 8 thousand different atom types based on first and second neighbors. Our results showed that atom types based on both first and second neighbors adequately capture the chemical environment, but atom types based on only first neighbors do not. For 3056 MOFs, we used density functional theory (DFT) followed by DDEC6 atomic population analysis to extract a host of important forcefield precursors: partial atomic charges; atom-in-material (AIM) C₆, C₈, and C₁₀ dispersion coefficients; AIM dipole and quadrupole moments; various AIM polarizabilities; quantum Drude oscillator parameters; AIM electron cloud parameters; etc. Electrostatic parameters were validated through comparisons to the DFT-computed electrostatic potential. These forcefield precursors should find widespread applications to developing MOF force fields.

Atom-in-material (AIM) partial charges, dipoles and quadrupoles, dispersion coefficients (C₆, C₈, C₁₀), polarizabilities, electron cloud parameters, radial moments, and atom types were extracted from quantum chemistry calculations for >3000 MOFs.     

Enhanced dispersibility of metal–organic frameworks (MOFs) in the organic phase via surface modification for TFN nanofiltration membrane preparation

The nanosized UiO-66-NH₂ metal–organic framework (MOF) material was synthesized and modified by palmitoyl chloride to enhance the dispersibility and restrain the aggregation of MOF particles in the organic phase. Then the above nanomaterial was introduced into interfacial polymerization to prepare thin film nanocomposite (TFN) nanofiltration membranes. The prepared membranes displayed “ridge-valley” shaped Turing structure surface morphology with membrane thickness around 380 nm. The FE-SEM, ATR-FTIR and XPS characterization showed the polyamide layer was fabricated on the substrate surface. The TFN membranes showed higher hydrophobicity, zeta potential and roughness than TFC membranes. Due to the introduction of MOF and the formation of MOF/polyamide interfacial passageways, the TFN membranes showed higher water permeability but slightly lower rejection properties than TFC membranes. Compared with the TFN membranes prepared from pristine UiO-66 and UiO-66-NH₂, the TFN membrane prepared from modified UiO-66-NH₂ showed better rejection properties because of its superior dispersibility in the organic phase.

The nanosized UiO-66-NH₂ metal–organic framework (MOF) material was synthesized and modified by palmitoyl chloride to enhance the dispersibility and restrain the aggregation of MOF particles in the organic phase.     

Optimization of metal–organic (citric acid) frameworks for controlled release of nutrients

Although polymer-coated controlled-release fertilizers have been under development for decades, their high costs, complex production processes, and potential environmental hazards have limited their application. Therefore, it is necessary to design and develop new materials for controlled nutrient release. In this study, two novel MOFs, compounds I and II, were successfully fabricated and optimized using ferric chloride, phosphoric acid, citric acid, and urea under hydrothermal conditions. The N, P, and Fe contents in compound I were 9.05%, 14.92%, and 14.55%, respectively, while the corresponding values in compound II were 10.78%, 14.10%, and 16.68%. The soil incubation results revealed that both compounds showed good slow-release longevity (more than 100 days). This study provides a new strategy for the fabrication of novel controlled-release fertilizers.

Novel MOFs were fabricated to control nutrient release under hydrothermal conditions, providing new strategies for the development of controlled-release fertilizers with relative low cost, simple production processes and little environmental impact.     

Strongly visible light-absorbing metal–organic frameworks functionalized by cyclometalated ruthenium(ii) complexes

Four different ruthenium(ii) complexes were incorporated into the metal–organic framework (MOF) UiO-67 using three different synthetic strategies: premade linker synthesis, postsynthetic functionalization, and postsynthetic linker exchange. One of these complexes was of the type (N–N)₃Ru²⁺, and three of the complexes were of the type (N–N)₂(N–C)Ru⁺, where N–N is a bipyridine-type ligand and N–C is a cyclometalated phenylpyridine-type ligand. The resulting materials were characterized by PXRD, SC-XRD (the postsynthetic functionalization MOFs), N₂ sorption, TGA-DSC, SEM, EDS, and UV-Vis spectroscopy, and were digested in base for subsequent ¹H NMR analysis. The absorption profiles of the MOFs that were functionalized with cyclometalated Ru(ii) complexes extend significantly further into the visible region of the spectrum compared to the absorption profiles of the MOFs that were functionalized with the non-cyclometalated reference, (N–N)₃Ru²⁺.

The metal–organic framework (MOF) UiO-67 was functionalized by incorporating different cyclometalated ruthenium(ii) complexes using three different methods: premade linker synthesis, postsynthetic functionalization, and postsynthetic linker exchange.     

Experimental investigation of the dehumidification and decarburization performance of metal–organic frameworks in solid adsorption air conditioning

Solid adsorption air conditioning systems use solid adsorption materials to co-adsorb water vapor and carbon dioxide, allowing the humidity and carbon dioxide concentration in the air-conditioned room to be controlled. Exploring the co-adsorption mechanism of H₂O and CO₂ is essential for the screening of adsorbent materials, system design, and system optimization in solid adsorption air conditioning systems. A fixed-bed adsorption–desorption device was built, and the dynamic adsorption properties of three MIL adsorbent materials MIL-101(Cr), MIL-101(Fe), and MIL-100(Fe) for co-adsorption of H₂O and CO₂ were studied. The results showed that all three MIL adsorbent materials are capable of performing co-adsorption of H₂O and CO₂ and meet the requirements of solid adsorption air conditioning systems. MIL-101(Cr) is recommended for solid adsorption air conditioners where dehumidification is the main focus, while MIL-100(Fe) is recommended for solid adsorption air conditioners where carbon removal is the main focus.

Solid adsorption air conditioning systems use solid adsorption materials to co-adsorb water vapor and carbon dioxide, allowing the humidity and carbon dioxide concentration in the air-conditioned room to be controlled.     

Strategies for the application of metal–organic frameworks in catalytic reactions

Efficient catalysts play crucial roles in various organic reactions and polymerization. Metal–organic frameworks (MOFs) have the merits of ultrahigh porosity, large surface area, dispersed polymetallic sites and modifiable linkers, which make them promising candidates for catalyzation. This review primarily summarizes the recent research progress on diverse strategies for tailoring MOFs that are endowed with excellent catalytic behavior. These strategies include utilizing MOFs as nanosized reaction channels, metal nodes decorated as catalytic active sites and the modification of ligands or linkers. All these make them highly attractive to various applications, especially in catalyzing organic reactions or polymerizations and they have proven to be effective catalysts for a wide variety of reactions. MOFs are still an evolving field with tremendous prospects; therefore, through the research and development of more modification and regulation strategies, MOFs will realize their wider practical application in the future.

Metal–organic frameworks (MOFs) are promising candidates for catalyzation. This review primarily summarized the recent research progress in diverse strategies for tailoring MOFs which are endowed with more excellent catalytic behavior.     

Synthesis of luminescent thorium-based metal–organic frameworks with 1,2,4,5-tetrakis(4-carboxyphenyl)benzene

Three new thorium-based MOFs based on 1,2,4,5-tetrakis(4-carboxyphenyl)benzene (H4TCPB) were obtained under a similar reaction system (metal salt, ligand, solvent, and acid are the same). Th(iv) forms the central unit of the MOFs in mononuclear and binuclear clusters, respectively. All the MOFs show blue ligand-based luminescence under an ultraviolet environment. This is the first time that multiple thorium-based MOFs with luminescence have been found with the same ligand.

Three new thorium-based MOFs based on 1,2,4,5-tetrakis(4-carboxyphenyl)benzene (H4TCPB) were obtained under a similar reaction system (metal salt, ligand, solvent, and acid are the same).     

Hydrogen adsorption mechanism of MOF-74 metal–organic frameworks: an insight from first principles calculations

The microscopic mechanism of the H₂ adsorption of two Mg-MOF-74 isoreticular frameworks, one with a benzenedicarboxylate (BDC) linker and the other with a dihydroxyfumarate (DHF) linker, were studied on the basis of density functional theory (DFT) method. Possible adsorption sites on the internal surface of the two MOFs were detected using ab initio molecular dynamics (AIMD) annealing simulations. The simulations were able to reproduce all adsorption sites which have been experimentally observed for the BDC-based M-MOF-74 frameworks with M = Ni and Zn. In descending order of binding strengths, they are the adsorption sites primarily induced by the open metal sites P₁, the oxygen atoms of the oxido groups P₂ and the aromatic rings P₃. The H₂–framework binding strengths were properly evaluated by taking into account the vibrational zero-point energy (ZPE) contribution. An additional type of adsorption sites induced by the oxygen atoms of the carboxyl groups P₄ is predicted for the Mg-MOF-74 framework. Two types of adsorption sites primarily induced by the open metal sites P₁ and oxygen atoms of the carboxyl groups P₂ were predicted for the DHF-based Mg-MOF-74 framework. Detailed analysis of the electron density showed that the electrostatic interaction of the H₂ molecule with the charge distribution of the local framework environment within a radius of ∼3.5 Å is a key factor to define adsorption positions and binding strength. The absence of the P₄ sites in the BDC-based Zn-MOF-74 framework is caused by the lower charge density at the oxygen atoms induced by less electro-positive metal. The substitution of the nonaromatic DHF linker for the aromatic BDC linker reduces the binding strength at the metal induced adsorption sites by 1.45 kJ mol⁻¹ due to the absence of the aromatic ring.

The microscopic mechanism of the H₂ adsorption of two Mg-MOF-74 isoreticular frameworks, one with a benzenedicarboxylate linker and the other with a dihydroxyfumarate linker, were studied on the basis of density functional theory (DFT) method.     

Growth inhibition of Microcystic aeruginosa by metal–organic frameworks: effect of variety,metal ion and organic ligand

Metal–organic frameworks (MOFs), as a new type of nanomaterial, have been rapidly developed and widely applied in the environmental area. However, the algae removal efficiency of MOFs, the effect of metal ions and organic ligands contained in MOFs and the stability of MOFs in water need further study. Based on the characteristics of algae, five types of MOFs, which were Cu-MOF-74, Zn-MOF-74, ZIF-8, Ag/AgCl@ZIF-8 and MIL-125(Ti) were synthesized and characterized by X-ray diffractometer (XRD), field emission scanning electron microscope (FESEM), and X-ray photoelectron spectroscopy (XPS). The effect of MOFs on the growth of Microcystis aeruginosa was comparatively studied, and the inhibition mechanism of MOFs on algae as well as the stability of MOFs was explored. Results showed that all of the as-synthetic MOFs had superior stability in water, and the order of stability of MOFs followed the order MIL-125(Ti) > Cu-MOF-74 > Ag/AgCl@ZIF-8 > ZIF-8 > Zn-MOF-74. The types of metal ions and organic ligands doped in MOFs have grade affected the inhibitory efficiency on the algae: containing Cu²⁺ and Ag⁺ ions, MOFs had more significant inhibitory capacity to algae than those containing Zn²⁺ ions; meanwhile, compared with MOFs which are assembled with 2,5-dihydroxyterephthalic acid (DHTA) organic ligands, MOFs containing 2-methylimidazole (GC) organic contributed to the removal of algae significantly. The order of inhibitory effects of algae by five MOFs follows the order Cu-MOF-74 > Ag/AgCl@ZIF-8 > ZIF-8 > Zn-MOF-74 > MIL-125(Ti). The physiological characteristics of algal cells were changed after being treated with different concentrations of Cu-MOF-74. Once the concentration of Cu-MOF-74 reached 1 mg L⁻¹, the algal cells began to be inhibited, the relative inhibition rate of algal cells at 120 h was over 400%, and the inhibition process fitted pseudo-second-order kinetic model well. The Cu²⁺ released by Cu-MOF-74 that the concentration higher than 1 mg L⁻¹ would lead to the destruction of algae cell morphology and the loss of cell integrity, causing cell contents to be partially released into the water, promoting the accumulation and precipitation of algal cells which were destabilizing already to achieve the purpose of inhibition of algae. In summary, MOFs can be used to inhibit the growth of cyanobacteria and have a promising application prospect.

MOFs have been applied in the inactivation of Microcystic aeruginosa. The algal suppression by MOFs depends on the presence of different metal ions and organic ligands.     

Zinc(ii) and cadmium(ii) amorphous metal–organic frameworks (aMOFs): study of activation process and high-pressure adsorption of greenhouse gases

Two novel amorphous metal–organic frameworks (aMOFs) with chemical composition {[Zn₂(MTA)]·4H₂O·3DMF}_n (UPJS-13) and {[Cd₂(MTA)]·5H₂O·4DMF}_n (UPJS-14) built from Zn(ii) and Cd(ii) ions and extended tetrahedral tetraazo-tetracarboxylic acid (H₄MTA) as a linker were prepared and characterised. Nitrogen adsorption measurements were performed on as-synthesized (AS), ethanol exchanged (EX) and freeze-dried (FD) materials at different activation temperatures of 60, 80, 100, 120, 150 and 200 °C to obtain the best textural properties. The largest surface areas of 830 m² g⁻¹ for UPJS-13 (FD) and 1057 m² g⁻¹ for UPJS-14 (FD) were calculated from the nitrogen adsorption isotherms for freeze-dried materials activated at mild activation temperature (80 °C). Subsequently, the prepared compounds were tested as adsorbents of greenhouse gases, carbon dioxide and methane, measured at high pressures. The maximal adsorption capacities were 30.01 wt% CO₂ and 4.84 wt% CH₄ for UPJS-13 (FD) and 24.56 wt% CO₂ and 6.38 wt% CH₄ for UPJS-14 (FD) at 20 bar and 30 °C.

Two novel amorphous metal–organic frameworks UPJS-13 and UPJS-14, constructed of Zn(ii)/Cd(ii) ions and extended tetrahedral linker were prepared, characterised and applied as adsorbents for carbon dioxide and methane.