Metal-organic Materials Research Articles

Remediation strategies for heavy metals contaminated ecosystem: A review

Industries and anthropogenic activities around us engender our natural resources with their noxious discharge, untreated waste water or sludge containing variety of heavy metals. These toxic metals in turn are emerging health risks for living beings triggering allergies, infection, defects and diseases. Consequently, there is evolving needs for ecologically safe, systematic and novel approach to remediate these toxic heavy metals. Physical, chemical and biological methods have not been much effective in dealing of contaminated ecosystem. These conventional approaches have limitation in terms of higher cost, energy consumption and less efficiency. Overcoming their drawbacks, adsorption, a physico-chemical surface phenomenon came to light which is a way cheaper, effective, flexible, reactive and efficient technique for eliminating heavy metals like cobalt, chromium, lead, nickel, mercury, arsenic, uranium, cadmium, copper etc. Modulating chemical and physical characteristics of microbes, lignocellulosic material, industrial waste biomass, nanotubes, metal organic frameworks (MOFs) and nanocomposite material, escorts in fabricating a magnificent adsorbent. This review critically evaluates various type of adsorbents, their application and adsorption efficiency. It also analysed the parameters affecting the adsorption processes.

Charge-transfer regulated visible light driven photocatalytic H2 production and CO2 reduction in tetrathiafulvalene based coordination polymer gel

The much-needed renewable alternatives to fossil fuel can be achieved efficiently and sustainably by converting solar energy to fuels via hydrogen generation from water or CO2 reduction. Herein, a soft processable metal-organic hybrid material is developed and studied for photocatalytic activity towards H2 production and CO2 reduction to CO and CH4 under visible light as well as direct sunlight irradiation. A tetrapodal low molecular weight gelator (LMWG) is synthesized by integrating tetrathiafulvalene (TTF) and terpyridine (TPY) derivatives through amide linkages and results in TPY-TTF LMWG. The TPY-TTF LMWG acts as a linker, and self-assembly of this gelator molecules with ZnII ions results in a coordination polymer gel (CPG); Zn-TPY-TTF. The Zn-TPY-TTF CPG shows high photocatalytic activity towards H2 production (530 μmol g−1h−1) and CO2 reduction to CO (438 μmol g−1h−1, selectivity > 99%) regulated by charge-transfer interactions. Furthermore, in situ stabilization of Pt nanoparticles on CPG (Pt@Zn-TPY-TTF) enhances H2 evolution (14727 μmol g−1h−1). Importantly, Pt@Zn-TPY-TTF CPG produces CH4 (292 μmol g−1h−1, selectivity > 97%) as CO2 reduction product instead of CO. The real-time CO2 reduction reaction is monitored by in situ DRIFT study, and the plausible mechanism is derived computationally.

Use of Modularity as a Principle of Design of Metal-organic Framework-based Materials with Specified Properties for Creating Modern Protective Equipment

An earlier analysis of approaches to the creation and improvement of protective materials and tissues made it possible to assume that the development of personal protective equipment (PPE) against various damaging factors of chemical, biological and physical nature can in future go towards the creation of modular organometallic frame structures (MOF-materials) with specific properties (from toxic chemicals and pathogenic microorganisms). The aim of this article is to develop and disclose the principle of modularity of construction of protective materials based on MOF-structures with specific properties. The principle of modularity of construction of protective materials with specific properties, proposed by us, is based on the use of single unified platform, on the surface of which special modules or combinations of modules are applied, which ensure the protection from various factors of chemical, biological and physical nature. The universal structure of MOF, called «MOF-universal», has been substantiated. The composition and properties of individual modules, possible and optimal combinations of modules of MOF-structures, the importance and significance of individual modules and their combinations for imparting universal protective properties to MOF-material are determined. The use of this principle will make it possible to impart protective properties to almost any clothing, while maintaining its physiological and hygienic characteristics and providing the required level of protection for personnel, without using specialized personal protective equipment.

Removal of boron in desalinated seawater by magnetic metal-organic frame-based composite materials: Modeling and optimizing based on methodologies of response surface and artificial neural network

A new type of metal organic frame-based magnetic composite adsorbent UiO-66-NH2/graphene oxide/Fe3O4 was used to eliminate the adverse effects of boron in the desalinated seawater. Through serial characterization, it was found that this adsorbent has the advantages of strong magnetic response, good pore structure and abundant functional groups. On the basis of single-factor experiments on various influencing factors, the simulation and prediction capabilities of the response surface method and artificial neural network method for the adsorption process were studied and compared. Both methods shown strong capacity to make effective prediction on the process of adsorption. However, the error of response surface method is smaller than the error of artificial neural network method. Result of optimization by response surface method shows that the optimal conditions of adsorbent dosage, pH, and temperature are 99.1 mg/L, 3.38 and 318 K. Following the above conditions, the boron adsorption capacity of the adsorbent obtained in the real desalinated seawater environment is 22.46 mg/g. In addition, the adsorbent shows good recyclability. Pseudo-second-order kinetic model, intra-particle diffusion model, and Langmuir isotherm model are all suitable for describing adsorption process. Thermodynamic research results reveal the fact that this process is spontaneous and endothermic, and the adsorption of boron by the adsorbent is a composite process consisting of physical adsorption and chemical adsorption.

Toward Liquid Phase Processable Metal Organic Frameworks: Dream or Reality?

ConspectusConventionally, the virtue of porosity is only given to porous solids. Metal Organic Frameworks (MOFs), carbon materials, or zeolites are some examples. However, processing these solids is not a straightforward task. Here, we discuss how to endow porous solids (MOFs) with liquid phase processability. More specifically, we show that surface modification of MOF crystals can lead to the formation of porous liquids (PLs) that can be further processed in the liquid phase. For instance, when placed in mesitylene, ZIF-67 predictably sediments. In contrast, with the adequate surface modification, stable dispersion of ZIF-67 can be achieved. Our proposed surface modification is facile and rapid. N-Heterocyclic carbenes are chosen as modifying agents as they are similar to imidazole linkers present on ZIFs. A simple stirring of a MOF and carbene mixture results in a modified solid. The morphology and textural properties of the modified MOF do not change from the ones of its parent. Since the porosity in solution remains unoccupied, the obtained stable colloids behave as porous liquids. Research into porous liquids is an emerging field that has already shown great promise in gases storage. Our breakthrough experiments show that these particular PLs have large potential for the separation of CO2/CH4 mixtures.The surface functionalized ZIF-67 could also be coprocessed with polymers to yield highly loaded Mixed-Matrix Membranes (MMMs) that cannot be achieved with a pristine MOF. Dispersions of functionalized ZIF-67 were blended with 6FDA-DAM and other homemade polymers in a shape of MMMs. While MMMs based on a pure MOF maintain good physical resistance at low loadings, increasing the concentration of MOF results in brittle composites. In contrast, MMMs made from functionalized ZIF retain good mechanical strength even at ca. 47.5 wt % loadings. Such high loading was possible to achieve due the better dispersion of the MOF particles during MMM fabrication and to the better affinity of the modified MOF with the polymer. The results obtained for this MMM are among the best MMMs ever reported for high challenging C3H6/C3H8 separation.The method is not limited to ZIF-67 but can be applied to a large body of MOFs that are constructed from imidazole-based linkers, as shown in this Account. The factors that determine whether a PL is formed include, but are not limited to, surface to volume ratio, framework particle size, and topology. On top of that, we propose potential strategies for the expansion of this method by carefully choosing surface modifiers that will suit other families of MOFs.

Conductive Composite Fiber with Customizable Functionalities for Energy Harvesting and Electronic Textiles.

A fiber-based triboelectric nanogenerator (F-TENG) is an important technology for smart wearables, where conductive materials and triboelectric materials are two essential components for the F-TENG. However, the different physicochemical properties between conductive metal materials and organic triboelectric materials often lead to interfacial failure problems, which is a great challenge for fabricating high-performance and stable F-TENGs. Herein, we designed a new conductive composite fiber (CCF) with customizable functionalities based on a core-spun yarn coating approach, which was applicable for a fiber-based TENG (CCF-TENG). By combing a core-spun method and a coating approach, triboelectric materials could be better incorporated on the surface of conductive fibers with the staple fibers to form a new composite structure with enhanced interfacial properties. The applicability of the method has been studied using different conductive and staple fibers and coating materials as well as different CCF diameters. As a demonstration, the open-circuit voltage and power density of the CCF-TENG reached 117 V and 213 mW/m2, respectively. Moreover, a 2D fabric TENG was woven and used as a wearable sensor for motion detection. This work provided a new method for 1D composite fibers with customizable functionalities for the applications in smart wearables.

Enantioselective Gel Phase Synthesis of Metal–Organic Materials

AbstractWe report the asymmetric synthesis of homochiral metal–organic materials (MOMs) in chiral gels from achiral components. The enantioselectivity of MOMs depends on the chirality of the gel, whereas the synthesis performed in solution phase and achiral gels resulted in conglomerates.

Enantioselective Gel Phase Synthesis of Metal-Organic Materials.

We report the asymmetric synthesis of homochiral metal-organic materials (MOMs) in chiral gels from achiral components. The enantioselectivity of MOMs depends on the chirality of the gel, whereas the synthesis performed in solution phase and achiral gels resulted in conglomerates.

Contribution of hydrogen bonding to liquid-phase adsorptive removal of hazardous organics with metal-organic framework-based materials

Removing hazardous organics from water or fuel is important for our clean environment; adsorption over porous materials has been a competitive means to eliminate such organics. Here, the adsorption or removal of hazardous organics with metal–organic framework-based adsorbents was explained, especially adsorption that relies on hydrogen bonding (H-bonding). The bonding details (direction, quantitative contribution, importance of 6-membered rings, and characterizations to support H-bonding) and improved performance via H-bonding were investigated. Finally, prospects for further development or research in the relevant fields were suggested.

Cascade/Parallel Biocatalysis via Multi-enzyme Encapsulation on Metal-Organic Materials for Rapid and Sustainable Biomass Degradation.

Multiple-enzyme cooperation simultaneously is an effective approach to biomass conversion and biodegradation. The challenge, however, lies in the interference of the involved enzymes with each other, especially when a protease is needed, and thus, the difficulty in reusing the enzymes; while extracting/synthesizing new enzymes costs energy and negative impact on the environment. Here, we present a unique approach to immobilize multiple enzymes, including a protease, on a metal-organic material (MOM) via co-precipitation in order to enhance the reusability and sustainability. We prove our strategy on the degradation of starch-containing polysaccharides (require two enzymes to degrade) and food proteins (require a protease to digest) before the quantification of total dietary fiber. As compared to the widely adopted "official" method, which requires the sequential addition of three enzymes under different conditions (pH/temperature), the three enzymes can be simultaneously immobilized on the surface of our MOM crystals to allow for contact with the large substrates (starch), while MOMs offer sufficient protection to the enzymes so that the reusability and long-term storage are improved. Furthermore, the same biodegradation can be carried out without adjusting the reaction condition, further reducing the reaction time. Remarkably, the simultaneous presence of all enzymes enhances the reaction efficiency by a factor of ∼3 as compared to the official method. To our best knowledge, this is the first experimental demonstration of using aqueous-phase co-precipitation to immobilize multiple enzymes for large-substrate biocatalysis. The significantly enhanced efficiency can potentially impact the food industry by reducing the labor requirement and enhancing enzyme cost efficiency, leading to reduced food cost. The reduced energy cost of extracting enzymes and adjusting reaction conditions minimize the negative impact on the environment. The strategy to prevent protease damage in a multi-enzyme system can be adapted to other biocatalytic reactions involving proteases.

Research progress in application of metal-organic framework-derived materials to sample pretreatment

样品前处理技术在复杂样品的整个分析过程中起着至关重要的作用,其不仅可以提高痕量目标物在样品中的浓度,而且能有效消除样品基质对分析的干扰。对于样品前处理技术而言,吸附剂是其最为核心部分。因此开发高效、稳定的新型吸附剂已成为前处理技术领域的研究热点。近年来,由金属有机骨架(metal-organic frameworks, MOFs)衍生的多孔材料因其形貌结构多样、孔径可调、比表面积高、热稳定性良好、耐化学腐蚀等优异性能,使其在样品前处理领域拥有广阔的应用前景,基于MOFs衍生材料的样品前处理新方法也层出不穷。然而,MOFs衍生材料仍存在MOFs前驱体合成工艺复杂、生产成本高、量产困难等问题。该文总结了近几年来MOFs衍生材料在分散固相萃取(dSPE)、磁固相萃取(MSPE)、固相微萃取(SPME)、搅拌棒固相萃取(SBSE)和分散微固相萃取(DMSPE)等样品前处理技术中的研究进展,并对多种MOFs衍生材料的制备方法、功能化调控、富集效率等方面进行了评述。最后,展望了MOFs衍生材料在该领域中的应用前景,为进一步研究MOFs衍生材料的应用提供了参考。

Electrochemical Detection of Sarcosine and Supercapacitor Based on a New Ni–Metal Organic Framework Electrode Material

A new Ni metal organic framework based on 2,2′-Biphenyldicarboxylic, 4,4′- bipyridine as linker is prepared by hydrothermal reaction and directly used as an electrode material for supercapacitor and the detection of sarcosine. [Ni3(BIPY)3(BPDA)2(HCOO)2(H2O)2]n (Ni-1; BIPY = 4,4′-bipyridine; BPDA = 2,2′-Biphenyldicarboxylate) displays the specific capacitance of the Ni-1 are 667 F/gat 1 A/g and retention is 82% of initial capacitance at 1 A/g. The excellent electrochemical property is ascribed to the intrinsic nature of Ni-1. Furthermore, the sarcosine sensing performance of the Ni-1 electrode is evaluated in 0.1 M of NaOH solution and the electrode showed a wider range of linear response 1 × 10−4 M to 1 × 10−3 M. Thus, the results show that the Ni-1 is a potential candidate for not only sensing of sarcosine but also supercapacitor application.

Synthesis of dielectric polymers with bipyridyl ligand and metal complex by ring-opening metathesis polymerization

Block copolymers with bipyridyl ligand and metal ion complex were synthesized by ring-opening metathesis polymerization. The combination of high dipolar polarization induced by bis(trifluoromethyl) group in polymer, the long-range polaron hopping process produced by the introduction of metal-bipyridyl side group, and the self-assembled nanostructure significantly improved the dielectric properties of polymers. The iridium(III)-contained block copolymer exhibited outstanding comprehensive dielectric and energy storage performance with high dielectric constant of 23.0–20.3 and low dielectric loss of 0.032–0.013 at 102–106 Hz, and high polarizability of 3.14 μC cm−2 at 280 MV m−1. Besides, the released-stored energy density reached 4.17/4.86 J cm−3 accompanied with the charge-discharge efficiency of 86%. Therefore, it would have potential applications as a metal-organic dielectric material with good dielectric and energy storage properties.

Can One Novel Series of Transition Metal Complexes of Oxy-dianiline Schiff Base Afford Advances in Both Biological Inorganic Chemistry and Materials Science?

ABSTRACT This paper provides a manifestation of a new tradition by which Comments on Inorganic Chemistry starts publishing original research content that, nonetheless, preserves the Journal’s identity as a niche for a critical discussion of contemporary literature in inorganic chemistry; for previous manifestations, see Comments Inorg. Chem. 2020, 40, 277-303 and references cited in the abstract thereof as Yaseen W. K.; Sanders S. F.; Almotawa R. M.; Otten B. M.; Bhat S.; Alamo D. C.; Marpu S. B.; Golden T. D.; Omary M. A. “Are Metal Complexes” Organic, Inorganic, Organometallic, or Metal-Organic Materials? A case Study for the Use of Trinuclear Coinage Metal Complexes as “Metal-Organic Coatings” for Corrosion Suppression on Aluminum Substrates Comments Inorg. Chem. 2019, 39, 1-26 and also, Mohapatra R. K.; Das P. K.; Pradhan M. K.; El-Ajaily M. M.; Das D.; Salem H. F.; Mahanta U.; Badhei G.; Parhi P. K.; Maihub A. A.; Kudrat -E-Zahan Md. “Recent Advances in Urea- and Thiourea-Based Metal Complexes: Biological, Sensor, Optical, and Corrosion Inhibition Studies” Comments Inorg. Chem. 2019, 39, 127-147). In this work, the Schiff base 1-(6-(1-((4-(4-aminophenoxy)phenyl)imino)ethyl)-pyridin-2-yl)ethan-1-one (L) and eight transition metal complexes were synthesized. The reaction of 4,4-oxy-dianiline with 2,6-diacetylpyridine in 1:1 molar ratio affords to the ligand which was employed in the synthesis of the corresponding metal complexes by reacting with the Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) chlorides in 1:1 molar ratio. All the compounds were characterized by using different analytical methods. Structures of complexes were found to be octahedral as deduced from the spectroscopic and magnetic moment measurements. The ligand behaves as a neutral tridentate ligand where it coordinated to metal ions through N-azomethine, N-pyridine, and O-carbonyl group. Besides, experimental investigations for their antibacterial activity against different bacteria species were studied, molecular docking studies were reported with receptors 4ME7, 4K3V, 3T88 and 4WJ3. Density functional theory (DFT) calculations for ligand were reported. Finally, the evaluation of corrosion inhibition efficiency was measured by using different techniques such as electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and electrochemical frequency modulation (EFM). Scanning electron microscope (SEM) and energy dispersive X-Ray analysis (EDX) were measured to affirm the presence of barrier film on the carbon steel surface by inspecting the surface morphologies and elemental composition of corrosion products.

Increasing exposure of atomically dispersed Ni sites via constructing hierarchically porous supports for enhanced electrochemical CO2 reduction

Atomically dispersed metal catalysts have been widely utilized for electrocatalysis, such as the electrochemical reduction of CO2, due to their low coordination number and maximum utilization of metal active sites. However, it remains a major challenge to develop an effective and convenient strategy for fully exposing the active sites of atomically dispersed metal catalysts within supports. Herein, we describe an operationally simple and sustainable strategy for preparing hierarchically porous thin-wall carbon networks with highly exposed atomically dispersed Ni sites by directly pyrolyzing a ground mixture of metal salts and organic ligands. Compared with the preformed metal organic framework-derived materials, the amount of exposed active Ni sites can be increased by ~50% for hierarchically porous materials. The hierarchically porous atomically dispersed Ni electrocatalyst shows obviously enhanced CO2RR catalytic performance with higher CO Faradaic efficiency (over 99% at −0.88 V) and high TOF value of 7025 h−1 (72.6% higher than that for the metal organic framework-derived materials). The excellent activity can be attributed to the increased exposure of atomically dispersed Ni sites with hierarchically porous structure and interconnected thin-wall carbon networks, which ensure the fully exposure of electrocatalytically active sites and promotion of mass transport and electron transfer. Density functional theory calculations further suggest that the fully exposed Ni sites are responsible for highly efficient activation of CO2 rather than the carbon layer-covered Ni sites.

Enhancing in the hydrogen storage by SWCNT/HKUST-1 composites: Effect of SWCNT amount

Functionalized single-walled carbon nanotubes into HKUST-1 ([Cu3-(btc)2]; btc= 1,3,5-benzenetricarboxylate) metal organic framework composite materials were synthesized by solvothermal method and characterized using different techniques such as XRD, BET,TG, SEM, and in situ Raman spectroscopy. It is important to mention that for the first time the thermal stability of the materials was determined by in situ Raman spectroscopy. Our results demonstrated that the incorporation of functionalized SWCNTs into HKUST-1 a slight increase in the thermal stability of MOF was observed. Too, a significant enhancement in the hydrogen adsorption capacity from 23.5% at 77 K and 1 bar of in the composite materials was observed. After of 5 cycles, hydrogen uptake is still above 2.98 wt% for 0.5SW/HKUST-1 sample. The hydrogen adsorption isotherms in the composite materials were completely reversible, reflecting only the physisorption of hydrogen molecule in the structure surface. Our results showed that the composite material with small amount of carbon nanotubes can be a promising candidate for the hydrogen storage.

Machine learning based simulation of water treatment using LDH/MOF nanocomposites

In this work we reported a novel methodology in prediction of molecular separation using adsorption process, and understanding the effect of underlying adsorption process on removal of pollutants from water. The data for adsorption of thallium (I) from water was collected and the model was developed based on machine learning (ML) approach. The type of adsorbent studied in this work is Ni50Co50-Layered double hydroxide/UiO-66-NH2 which is a metal organic framework-based nanocomposite material. The adsorbent was selected due to its high capacity in separation and removal of thallium (I) from aqueous solutions with surface area of around 900 m2/g and pore volume of 0.9 cc/g. The modeling and computations were performed using artificial neural network which is a machine learning technique considering the equilibrium concentration of ion in the liquid solution at equilibrium as the main output. Two inputs were considered including temperature and the initial concentration of the adsorbate. The training and validation of the model indicated very high accuracy of the model compared to other modeling approaches with high determination coefficient (R2) more than 0.99 for both training and testing the model stages.

From n- to p-Type Material: Effect of Metal Ion on Charge Transport in Metal-Organic Materials.

An intriguing new class of two-dimensional (2D) materials based on metal-organic frameworks (MOFs) has recently been developed that displays electrical conductivity, a rarity among these nanoporous materials. The emergence of conducting MOFs raises questions about their fundamental electronic properties, but few studies exist in this regard. Here, we present an integrated theory and experimental investigation to probe the effects of metal substitution on the charge transport properties of M-HITP, where M = Ni or Pt and HITP = 2,3,6,7,10,11-hexaiminotriphenylene. The results show that the identity of the M-HITP majority charge carrier can be changed without intentional introduction of electronically active dopants. We observe that the selection of the metal ion substantially affects charge transport. Using the known structure, Ni-HITP, we synthesized a new amorphous material, a-Pt-HITP, which although amorphous is nevertheless found to be porous upon desolvation. Importantly, this new material exhibits p-type charge transport behavior, unlike Ni-HITP, which displays n-type charge transport. These results demonstrate that both p- and n-type materials can be achieved within the same MOF topology through appropriate choice of the metal ion.

A hydrolytically stable hydrogen-bonded inorganic-organic network as a luminescence turn-on sensor for the detection of Bi3+ and Fe3+ cations in water

Metal-organic materials capable of turn-on sensing of metal ions in water are highly desirable but relatively infrequently reported. Herein, a hydrogen-bonded inorganic-organic network based on Cu(I) ions and luminescent organic ligands, namely Cu-HBIBA (HBIBA = 4-[bis-(4-imidazol-1-ylphenyl)amino]benzoic acid), was synthesized and applied to detect trivalent metal ions (Fe3+ and Bi3+) in aqueous solution. Cu-HBIBA is a binuclear complex and exhibits an interesting hydrogen-bonded 1D → 2D polythreading array. Notably, Cu-HBIBA has good stability at pH values from 2 to 12 and is hardlysoluble in aqueous solution. Cu-HBIBA shows luminescence enhancement in the presence of Fe3+, and Bi3+ ions and shows high selectivity and sensitivity with detection limits of 0.16 µM and 43 nM for Fe3+ and Bi3+, respectively. The hydrolytic stability, inhibited ligand-based luminescence and uncoordinated carboxylate groups in the network may contribute to the sensing performance of Cu-HBIBA. A mechanistic study indicates that the Cu-HBIBA crystal adsorbs metal ions via the carboxyl groups on its surface, leading to inhibition of the photoelectron transfer (PET) process, recovery of the luminescent emissions of the ligand and realization of turn-on luminescence detection.

Coordination Properties of Hydroxyisophthalic Acids: Topological Correlations, Synthesis, Structural Analysis, and Properties of New Complexes.

Hydroxyisophthalic acids are valuable polytopic ligands for the design of functional materials based on coordination polymers due to the variety of charges and coordination modes they possess. Herein, we describe the synthesis, thermal stability, nonlinear optical (NLO) and spectroscopic properties of five novel coordination compounds, [K2 L(H2 O)2 ], [MgL(H2 O)2 ] ⋅ 3H2 O, [CaL(H2 O)3 ], [SrL(H2 O)3 ] ⋅ H2 O, [BaL(H2 O)(H2 O)5 ], and one salt, (NH4 )2 L ⋅ 2H2 O, with 4,5,6-trihydroxyisophthalic acid (H2 L), which has not been tested in assembling crystalline coordination networks before. The peculiarities of the structural organization of the compounds were analyzed and compared with those for other hydroxyisophthalates. The coordination properties of hydroxyisophthalic acids were studied from the topological point of view, and a comparative topological analysis of coordination and H-bonded networks was performed. Structural correlations revealed in this study could be useful for the design of hydroxyisophthalate-based coordination networks, including porous metal-organic frameworks, proton conductors, and NLO materials.