Microporous Metal-organic Framework Research Articles

Insights into a New Multi‐Stimuli‐Responsive Photochromic Metal‐Organic Framework: Highly Sensitive Turn‐On Luminescence in a Lanthanum Phosphonate

AbstractThe new microporous metal organic framework [La2(H2O)5(H2TPPE)]·3H2O (CAU‐54), is obtained in a hydrothermal reaction of the linker 1,1,2,2‐tetrakis(4′‐phosphonophenyl)ethylene (H8TPPE) and La3+ ions. The extensive characterization including temperature‐dependent crystal structures and spectroscopic properties allowed to understand the unique, multi‐responsive material properties. CAU‐54 exhibits rarely observed reversible photochromism as well as turn‐on photoluminescence by various external chemical or physical stimuli including change of pressure, solvent exchange, and temperature variation. These properties can be unequivocally assigned to the presence of tetraphenylethylene (TPE) moieties of the linker molecules within the MOF, i.e., the ordered spatial arrangement of the linker molecules, the presence of accessible pores as well as the coordination flexibility of the phosphonate groups and the rotational freedom of the linker. By temperature‐dependent steady‐state and time‐resolved luminescence studies, it is shown that this compound exhibits a) blue fluorescence that becomes effectively quenched at room temperature, b) green efficient luminescence with thermal stability up to 400 K, and c) red phosphorescence correlated to the observed photochromism. In addition, CAU‐54 shows unusual thermal expansion properties as shown by temperature‐dependent powder X‐ray diffraction measurements with identified transition points that correlate with the observed temperature‐dependent changes in the photoluminescence.

A Microporous Mn(II) MOF Based on 5-(4H-1,2,4-triazol-4-yl) Isophthalic Acid for CO2/N2 Separation.

Removal of carbon dioxide (CO2) from a CO2/N2 mixture by utilizing CO2-selective sorbents is important from the perspective of energy security and environmental sustainability. Herein, a microporous metal-organic framework (MOF) composed of manganese(II) and a bifunctional linker 5-(4H-1,2,4-triazol-4-yl)benzene-1,3-dicarboxylic acid (H2L), [Mn(HL)2] (1) is designed and synthesized using a hydrothermal method. Characterized by single-crystal X-ray diffraction (SCXRD), a microporous channel was found in the structure of compound 1 along the a-axis. Attributed to hydrogen-binding interactions between CO2 molecules and N- and O-donor ligands in its microporous one-dimensional (1D) channel, compound 1 exhibits favorable adsorption of CO2 over N2. Further, verified by experimental breakthrough tests, the CO2/N2 mixture can be separated efficiently. This work provides potential guidance for designing CO2-selective MOFs for CO2/N2 separation.

Dehydration‐Induced Cluster Consolidation in a Metal–Organic Framework for Sieving Hexane Isomers

Metal–organic frameworks (MOFs) that exhibit dynamic phase‐transition behavior under external stimuli could have great potential in adsorptive separations. Here we report on a zinc‐based microporous MOF (JNU‐80) and its reversible transformation between two crystalline phases: large pore (JNU‐80‐LP) and narrow pore (JNU‐80‐NP). Specifically, JNU‐80‐LP can undergo a dehydration‐induced cluster consolidation under heat treatment, resulting in JNU‐80‐NP with a reduced channel that allows exclusion of di‐branched hexane isomers while high adsorption of linear and mono‐branched hexane isomers. We further demonstrate the fabrication of MOF‐polymer composite (JNU‐80‐NP‐block) and its application in the purification of di‐branched isomers from liquid‐phase hexane mixtures (98% di‐branched) at room temperature, affording the di‐branched hexane isomers with 99.5% purity and close to 90% recovery rate over ten cycles. This work illustrates an interesting dehydration‐induced cluster consolidation in MOF structure and the ensuing channel shrinkage for sieving di‐branched hexane isomers, which may have important implications for the development of MOFs with dynamic behavior and their potential applications in non‐thermal driven separation technologies.

Dehydration-Induced Cluster Consolidation in a Metal-Organic Framework for Sieving Hexane Isomers.

Metal-organic frameworks (MOFs) that exhibit dynamic phase-transition behavior under external stimuli could have great potential in adsorptive separations. Here we report on a zinc-based microporous MOF (JNU-80) and its reversible transformation between two crystalline phases: large pore (JNU-80-LP) and narrow pore (JNU-80-NP). Specifically, JNU-80-LP can undergo a dehydration-induced cluster consolidation under heat treatment, resulting in JNU-80-NP with a reduced channel that allows exclusion of di-branched hexane isomers while high adsorption of linear and mono-branched hexane isomers. We further demonstrate the fabrication of MOF-polymer composite (JNU-80-NP-block) and its application in the purification of di-branched isomers from liquid-phase hexane mixtures (98% di-branched) at room temperature, affording the di-branched hexane isomers with 99.5% purity and close to 90% recovery rate over ten cycles. This work illustrates an interesting dehydration-induced cluster consolidation in MOF structure and the ensuing channel shrinkage for sieving di-branched hexane isomers, which may have important implications for the development of MOFs with dynamic behavior and their potential applications in non-thermal driven separation technologies.

Efficient C2H2/CO2 separation in two 2-fold interpenetrating metal-organic frameworks with ultrahigh C2H2 packing density

Adsorptive separation of C2H2/CO2 is industrially important and feasible but the design of highly efficient adsorbents remains very challenging owing to the almost identical physicochemical properties of the two gases. Herein, we constructed two new microporous metal–organic frameworks (MOFs), termed CTGU-39/40 (CTGU = China Three Gorges University), with 2-fold interpenetrating frameworks and unique pore geometry/chemistry for C2H2/CO2 separation. Both the activated MOFs (CTGU-39/40-a) can preferentially adsorb C2H2 over CO2 with excellent selectivity of 8.4 and 3.3 at 298 K and 100 kPa, respectively, as verified by static adsorption measurements. More importantly, attributed to the suitable pore aperture size (∼5 Å) and abundant adsorption sites, CTGU-39-a combines exceptionally high packing density of C2H2 (0.41 g mL−1) and moderate isosteric heat of adsorption (Qst) for C2H2 (26.8 kJ mol−1), outperforming most previously reported adsorbents. Theoretical calculations reveal that the preferential adsorption of C2H2 within two MOFs is driven by cooperative adsorption behavior through multiple H-bonding and Coulomb interactions. Experimental breakthrough results further confirmed their practical separation ability and recyclability toward an equimolar C2H2/CO2 mixture at different feeding rates. This work may offer new insights into the design of advanced porous materials for C2H2 purification and potentially other gas separations.

Effects of Particle Size on the Gas Uptake Kinetics and Physical Properties of Type III Porous Liquids.

Type III porous liquids (PLs) consist of porous solid particles dispersed in a size-excluded liquid phase and are attracting much attention as novel media for applications such as gas separation. However, the effects of fundamental variables such as particle size on their physical properties are currently largely unknown. Here we study the effects of particle size in a series of porous liquids based on solid Al(OH)(fumarate) (a microporous metal-organic framework, MOF) with particle sizes of 60 nm, 200-600 nm, or 800-1000 dispersed in liquid polydimethylsiloxane (PDMS). Properties examined include physical stability of the dispersion, viscosity, total CO2 uptake, and kinetics of CO2 uptake. As expected, both physical stability and viscosity decreased with increasing particle size. Unexpectedly, total gravimetric gas uptake also varied with particle size, being greatest for the largest particles, which we ascribe to larger particles having a lower relative content of surface-bound FMA ligands. Various models for the gas uptake kinetic data were considered, specifically adsorption reaction models such as pseudo-first-order, pseudo-second-order, and Elovich models. In contrast to pure PDMS, which showed first-order kinetics, all PLs fit best to the Elovich model confirming that their uptake mechanism is more complex than for a simple liquid. Adsorption diffusion models, specifically Weber and Morris' intraparticle model and Boyd's model, were also applied which revealed a three-step process in which a combination of diffusion through a surface layer and intraparticle diffusion were rate-limiting. The rate of gas uptake follows the order PDMS < PL1 < PL2 < PL3, showing that the porous liquids take up gas more rapidly than does PDMS and that this rate increases with particle size. Overall, the study suggests that for high gas uptake and fast uptake kinetics, large particles may be preferred. Also, the fact that large particles resulted in low viscosity may be advantageous in reducing the pumping energy needed in flow separation systems. Therefore, the work suggests that finding ways to stabilize PLs with large particles against phase separation could be advantageous for optimizing the properties of PLs toward applications.

Heterovalent Metal Pair Sites on Metal-Organic Framework Ordered Macropores for Multimolecular Co-Activation.

The precise design of catalytic metal centers with multiple chemical states to facilitate sophisticated reactions involving multimolecular activation is highly desirable but challenging. Herein, we report an ordered macroporous catalyst with heterovalent metal pair (HMP) sites comprising CuII-CuI on the basis of a microporous metal-organic framework (MOF) system. This macroporous HMP catalyst with proximity heterovalent dual copper sites, whose distance is controlled to ∼2.6 Å, on macropore surface exhibits a co-activation behavior of ethanol at CuII and alkyne at CuI, and avoids microporous restriction, thereby promoting additive-free alkyne hydroboration reaction. The desired yield enhances dramatically compared with the pristine MOF and ordered macroporous MOF both with solely isovalent CuII-CuII sites. Density functional theory calculations reveal that the Cu-HMP sites can stabilize the Bpin-CuII-CuI-alkyne intermediate and facilitate C-B bond formation, resulting in a smooth alkyne hydroboration process. This work provides new perspectives to design multimolecular activation catalysts for sophisticated matter transformations.

Defective ordered macroporous ZIF–8/ZnO heterostructure for enhanced visible–light photo–oxidation performance

Metal–organic frameworks (MOFs) have been extensively used for catalytic reactions due to their abundant structures, regular reticulated channels, and high specific surface areas. They are good platforms for the fabrication of various composites, including metals, oxides, or carbides. Therefore, MOFs can be used as templates to fabricate heterostructures with excellent photocatalytic performance. In this study, the defective ordered macroporous Zeolitic Imidazolate Framework–8/ZnO (D–OM–ZIF–8/ZnO) heterostructure is constructed through the in situ conversion of ordered macroporous ZIF–8 (OM–ZIF–8). The introduction of self–defects into OM–ZIF–8 results in a wide visible–light response band. The ZnO nanoparticles that have formed on the surface of OM–ZIF–8 can effectively regulate surfaces and interfacial states and then construct the heterostructure. The ordered macroporous structure shows considerable advantages for improving carrier mobility, mass transfer rate, and light utilization during photocatalysis. D–OM–ZIF–8/ZnO demonstrates remarkable photocatalytic degradation activity for tetracycline and methylene blue under visible–light. Therefore, our novel construction strategy opens a door for designing ordered microporous MOF–based heterostructures as potential visible–light photocatalysts.

Insights on MOF-derived metal-carbon nanostructures for oxygen evolution.

Electrochemical water splitting has been regarded a promising method for the production of green hydrogen, addressing the need for efficient energy conversion and storage. However, it is severely hindered by the oxygen evolution reaction (OER) because of its multi-step four-electron transfer pathway with sluggish reaction kinetics. Microporous metal-organic-frameworks (MOFs), by virtue of large specific surface area, high porosity, tunable composition and morphology, find widespread use as precursors of metal-carbon nanostructures. The resulting carbon nanomaterials can well inherit the characteristics and advantages of the crystalline MOF precursors, and exhibit versatile application prospects in the fields of environment and energy, particularly in OER. Herein, a meticulous overview of the synthesis strategy for MOF-derived metal-carbon nanostructures and the origins of their enhanced OER properties has been demonstrated. We comprehensively illustrate these aspects across three dimensions: MOF selection, metal introduction, and carbon structures. Finally, the challenges and future prospects for this emerging field will be presented.

A microporous bismuth-based MOF for efficient separation of acetylene from carbon dioxide.

The separation of acetylene from carbon dioxide is challenging due to their almost identical molecular sizes and volatilities. Metal-organic frameworks (MOFs) in general are strong candidates for the separation of gas mixtures owing to the presence of functional pore surfaces that can selectively capture specific target molecules. Herein, we report a stable and easily synthesized bismuth-based MOF, Bi-BTC, which can achieve the separation of acetylene and carbon dioxide. We performed a detailed analysis of the sorption properties of the Bi-MOF. Bi-BTC shows good adsorption capacities for C2H2 with a capacity of 53.8 cm3 g-1 at 298 K and 1.0 bar, and C2H2/CO2 selectivity of 5.14/7.69 at 298 K and 1.0/0.1 bar. IAST selectivity calculations indicate that Bi-BTC possesses good separation capacity, and dynamic breakthrough experiments were performed to prove the separation of C2H2 and CO2. Bi-MOFs as a group of relatively less studied types of MOFs have interesting adsorption characteristics, and this study on Bi-based MOF will enrich three-dimensional Bi-MOF adsorbents for gas adsorption and separation applications.

Two Ln-MOFs containing abundant Lewis acid sites as the efficient and heterogeneous catalyst to activate epoxides for cycloaddition of CO2

The burning of a large number of fossil fuels leads to the increase of CO2 content in the air, causing environmental problems such as greenhouse effect and ocean acidification, which has attracted wide attention. It is of great significance to utilize microporous metal-organic frameworks (MOFs) for carbon dioxide conversion and utilization. Herein, two MOFs {[Ln(dppa)(H2O)2·2H2O]·dima·H2O·0.5O} (1: Sm-MOF; 2: Gd-MOF; H4dppa = 5-(3′ 4′-dicar- boxylphenoxy) isophthalic acid, dima = dimethylamine, which is decomposed by DMF hydrothermal reaction), and its structural characterization and CO2 catalytic conversion performance were studied. The BET test of MOFs 1–2 shows that it has good microporosity. At 273 K and 298 K, MOFs 1–2 showed lower adsorption capacity for CH4, but higher adsorption capacity for CO2. The adsorption enthalpy of CO2 was calculated by Virial equation, and the adsorption selectivity of CO2 at different separation ratios was discussed respectively. The heterogeneity of MOFs 1–2 was proved by thermal filtration experiments. The reproducibility test shows that the catalyst structure is still intact after five cycles, indicating that the catalyst still has good repeatability. In addition, the catalytic mechanism of cycloaddition reaction was discussed.

Anisotropic Interface Successive Assembly for Bowl-Shaped Metal-Organic Framework Nanoreactors with Precisely Controllable Meso-/Microporous Nanodomains.

Colloidal metal-organic framework (MOF) nanoparticles, with tailored asymmetric nanoarchitectures and hierarchical meso-/microporosities, have significant implications in high-performance nanocatalysts, nanoencapsulation carriers, and intricate assembly architectures. However, the methodology that could achieve precise control over the anisotropic growth of asymmetric MOF particles with tailored distributions of meso- and microporous regions has not yet been established. In this study, we introduce a facile anisotropic interface successive assembly approach to synthesize asymmetric core-shell MOF (ZIF-67) nanobowls with worm-like mesopores in the core and intrinsic micropores in the shell. Our synthesis pathway relies on anisotropic nucleation of mesoporous MOF nanohemispheres on emulsion interfaces through the cooperative assembly of surfactants and MOF precursors. This is followed by the growth of microporous MOF layers on both interfaces of mesoporous cores and emulsion droplets, resulting in a hierarchically porous core-shell nanostructure. By utilizing this multi-interface-driven approach, we enable the creation of diverse geometries and distributions of mesopores and micropores in asymmetric MOF nanoarchitectures. The obtained bowl-like meso-/microporous core-shell ZIF-67 particles exhibit enhanced catalytic activity for CO2 cycloaddition, attributed to reactant accumulation within the bowl-like architecture, active site accessibility in the open mesoporous core, and improved structural stability. Overall, our study provides insights and inspiration for exploring the intricate asymmetric nanostructures of hierarchically porous MOFs with diverse potential applications.

Highly effective quantum sieving of hydrogen isotopes on flexible metal-organic frameworks with mobile ligands

The separation of hydrogen isotopes is crucial in nuclear energy and biomedicine, but current techniques have limited separation coefficients. Utilizing flexible metal-organic frameworks (MOFs) with quantum sieving capabilities offers a promising solution. However, achieving high hydrogen isotope adsorption capacity while maintaining a high separation factor remains a challenge. This study presents a novel approach for the quantum sieving of hydrogen isotopes using MOFs with mobile ligands. The stable crystal structure of the microporous MOFs enables large hydrogen isotope adsorption capacity. The presence of mobile ligands acts as the gate in the dynamic adsorption and separation process, enhancing the performance of hydrogen isotope separation. The smaller quantum radius and larger molecular weight of deuterium facilitate its easier entry into the micropores, resulting in a maximum selectivity for D2 over H2 of 36.7 and a D2 uptake of 17.3 mmol g−1. Furthermore, the kinetic quantum sieving of hydrogen isotopes necessitates MOFs with mobile ligands that maintain their flexibility from 20 K to 70 K, as demonstrated by ultralow-frequency Raman spectra.

A quad-core Zn (II) cluster-based microporous metal-organic framework with nonpolar cages for efficient removal of ethane from ethane/ethylene mixtures

Ethane (C2H6) and ethylene (C2H4) have similar physical and chemical properties, which are critical and difficult for the separation of C2H6/C2H4 mixtures in the petrochemical process. Traditional C2H4-selective adsorbents can separate the C2H6/C2H4 mixtures, but need further desorption treatment to obtain pure C2H4 production. On the contrary, high-pure C2H4 can be prepared in one step by C2H6-selective porous material. Herein, we present a caged metal-organic framework (GNU-2) based on Zn (II) clusters, which has advantageous adsorption sites and cavity pockets for the reverse capture of C2H6 from C2H6/C2H4 mixtures. At 298 K and 1 bar, high C2H6 uptake (5.10 mmol g−1) and C2H6/C2H4 selectivity (1.849) were attained based on the activated GNU-2 (GNU-2a), exceeding a number of top C2H6-selective adsorbents. Grand canonical Monte Carlo (GCMC) simulations exhibit that the appropriate chemical environment of nonpolar cage in GNU-2a allows it to continuously maintain closer van der Waals contacts between C2H6 molecule, saturated Zn cluster and nonpolar pore surface through multiple CH···O hydrogen interactions and CH···π hydrogen interactions. Moreover, dynamic breakthrough studies also show that GNU-2a displays the actual separation performances of C2H6.

High yield, large-scale synthesis of calcium-based microporous metal-organic framework and examination of the long-term stability for xenon adsorption applications

Scale-up synthesis of calcium-based microporous metal-organic framework (SBMOF-1) up to ∼400 g in a batch with a yield of >90 % was achieved by a solvothermal reaction of sulfonyldibenzoic acid (SDB) with an excess of calcium chloride. Here, we observed that recrystallization of unreacted SDB at a solvothermal condition caused a moderate reaction yield (40–50 %) at the reference condition of CCaCl2/ CSDB = 1 and CSDB/ CSDB(ref) = 1. Simply adding more reagents to the reactor did not increase the mass of product formed per unit volume due to a more pronounced loss of the yield at those conditions. By simultaneously changing the molar ratio of CaCl2 to SDB, CCaCl2/ CSDB, and the molar concentration of the SDB reagent, CSDB/ CSDB(ref), we explored %yield of the reaction. Interestingly, a linear improvement in the yield was observed from 21 % (at CCaCl2/ CSDB = 0.5) up to 78 % (at CCaCl2/ CSDB = 6) at a fixed ratio of CSDB/ CSDB(ref) = 2 and the yield leveled off after further addition. Unlike those at CCaCl2/ CSDB = 1, the yields at a high CaCl2 excess continued to improve with increasing the CSDB/ CSDB(ref). When a large pressure vessel (2500 mL EtOH, CCaCl2/ CSDB = 6, CSDB/ CSDB(ref) = 8) was used, about 415 g of SBMOF-1 with a yield of 92.3 % was produced, indicating 16 × the space yield improvement. The ability to synthesize SBMOF-1 on a large scale allowed us to examine the long-term stability of SBMOF-1 for almost 200 days in the presence of varying levels of relative humidity.

Efficient C2H2/CO2 and C2H2/C2H4 separations in a novel fluorinated metal–organic framework

Separating acetylene (C2H2) from carbon dioxide (CO2) and ethylene (C2H4) presents a significant challenge in the industry due to their closely similar physical properties. Herein, we synthesized a novel [NbOF5]2- pillared microporous metal–organic framework ZNU-11 with abundant electronegative sites for efficient C2H2/CO2 and C2H2/C2H4 adsorption separation. The uncoordinating fluorine atoms in the confined pores selectively capture C2H2 from CO2 and C2H4 by hydrogen bonding interactions. The C2H2 capacity of ZNU-11 is 45.5 cm3/g at 298 K and 100 kPa, over three folds of the C2H4 uptake and two folds of the CO2 uptake. The relatively modest C2H2 adsorption heat of 36.1 kJ/mol facilitates the straightforward desorption and regeneration of ZNU-11. Furthermore, density functional theory (DFT) calculations confirmed the stronger binding of C2H2 compared to CO2 and C2H4. Experimental breakthroughs with C2H2/CO2 and C2H2/C2H4 gas mixtures, coupled with excellent recyclability, validated the practical separation performance of ZNU-11. Notably, the dynamic separation factor of 4.2 for equimolar C2H2/CO2 mixture rivals those of many benchmark materials.

Synthesis and characterization of Zn-based bimetallic microporous MOF composites for effective formaldehyde sensing at room temperature

In the present work, we fabricated 1:1 bimetallic ZnCu(NA); ZnCd(NA); and ZnCo(NA) metal organic frameworks (MOFs) using nicotinic acid (NA) as organic linker by solvothermal method. All the compounds were characterized by Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, X-ray photoelectron Spectroscopy (XPS), and scanning electron microscopy (SEM).The drop-casting method used to develop a chemiresistive sensor to sense Volatile Organic Compounds (VOCs) at room temperature. These bimetallic sensors exhibited excellent sensitivity and good linearity in detecting formaldehyde at 1 to 50 ppm range. The responses of all sensing materials towards formaldehyde gas at 50 ppm concentration are Cu(NA) 3.74, ZnCu(NA) 18.6, Cd(NA) 3.13, ZnCd(NA) 8.36 and ZnCo(NA) 28.3.The sensing times of Cu(NA), ZnCu(NA), Cd(NA), ZnCd(NA) and ZnCo(NA) are 17, 9, 15, 18 and 17 respectively. These results demonstrate the potential applications of bimetallic Zn/Cu, Zn/Cd, and Zn/Co MOFs for sensitive and specific formaldehyde detection at ambient temperature. These results show that ZnCo(NA) sensing material is an excellent selective sensor for formaldehyde sensing.

Highly sensitive self-powered piezoelectric poly(vinylidene fluoride)-based nanofibrous mat containing microporous metal–organic framework nanostructures for energy harvesting applications

Highly sensitive self-powered piezoelectric poly(vinylidene fluoride)-based nanofibrous mat containing microporous metal–organic framework nanostructures for energy harvesting applications

Solvent-Directed Construction of a Nanoporous Metal-Organic Framework with Potential in Selective Adsorption and Separation of Gas Mixtures Studied by Grand Canonical Monte Carlo Simulations.

In this report, a microporous metal-organic framework of [Ca(TDC)(DMA)]n (1) and a two-dimensional coordination polymer of [Ca(TDC)(DMF)2 ]n (2), (TDC2- =Thiophene-2,5-dicarboxylate, DMA=N, N'-dimethylacetamide and DMF=N, N'-dimethylformamide) based on Ca(II) were designed by the effect of solvent, and X-ray analysis was performed for the single crystals of 1 and 2. Then, compound 1 was synthesized in three different methods and identified with a set of analyses. Compared to other adsorbents, MOFs are widely used in the field of adsorption and separation of various gases due to a series of distinctive features such as diverse and adjustable structures pores with different dimensions, high porosity and surface area with regular distribution of active sites. Therefore, the ability of 1 to uptake single gases (CH4 , CO2 , C2 H2 , H2, and N2 ) and separation of several binary mixtures of gases (CO2 /CH4 , CO2 /N2 , CO2 /H2 and CO2 /C2 H2 ), were investigated using Grand Canonical Monte Carlo simulations. Volumetric and gravimetric adsorption isotherms in various operating conditions, the isosteric heat of adsorption (qst ), the chemical potential for each thermodynamic state, and snapshots during the simulation process were reported in all cases. The results obtained from the adsorption simulation indicate that compound 1 has a high capacity for uptake of H2 (16 mmol g-1 ) and N2 (12.5 mmol g-1 ), CO2 (6.6 mmol g-1 ), C2 H2 (5 mmol g-1 ) and CH4 (1.5 mmol g-1 ) gases at 1 bar. It also performs well in separating CO2 in binary mixtures, which can be attributed to the presence of open metal sites in nodes of 1 and their electrostatic tendency to interact with CO2 containing the higher quadrupole dipole moment compared to other components of the mixture.

UiO-66 octahedrons for adsorptive removal of direct blue-6: process optimization, interaction mechanism, and phytotoxicity assessment.

The materials for water treatment have been evolving in multitude of dimensions, indicating the importance of water reuse and increasing level of water pollution around the globe. Among the various materials that are utilized in wastewater treatment, the material that has attracted the research community for the past decades is the metal organic framework (MOF). In this work one of the water stable and microporous MOF, UiO-66, and its aminated version has been employed to adsorb an anionic azo dye, direct blue-6 (DB-6), from the aqueous matrix. Performance of both the MOFs was compared to know the efficiency under varying solution conditions. The optimized parameters for DB-6 adsorption by UiO-66 was performed using response surface methodology. This numerical optimization was further extended with canonical and ridge analysis. Under optimal conditions, the materials were exhibiting a good adsorption capacity of 754.4mg/g. The materials were analyzed in terms of morphology, crystallinity, thermal stability, and surface area using instruments like X-ray diffraction, electron microscopy, thermogravimetric analysis, and BET surface area analysis. The mechanism of interaction between UiO-66 and DB-6 molecule was elucidated with the help of XPS analysis which helps to know the main interacting group of UiO-66. This study was concluded with a phytotoxicity analysis of DB-6 and the antioxidant system of Vigna radiata assessed using pre and post adsorbed water.