Dual-ligand Strategy Research Articles

Construction of two isomorphic multifunctional MOFs via a dual-ligand strategy for aromatic compounds detection and photocatalytic degradation performance

The development of multifunctional and structurally unique metal−organic frameworks (MOFs) presents a highly attractive yet challenging endeavor for chemists. In this study, we employ a dual-ligand strategy to synthesize two isomorphic Co/Zn MOFs, {[Co4(BMIP)3(MIP)4]·3DMF·H2O}n (SNUT-35-Co) and {[Zn4(BMIP)3(MIP)4]·2DMF·2H2O}n (SNUT-35-Zn). The photocatalytic performance of SNUT-35-Co and SNUT-35-Zn was evaluated using methylene blue (MB). Under UV/visible-light irradiation, the photocatalytic decolorization rates of MB for SNUT-35-Co and SNUT-35-Zn reached 95% within 140 min and 120 min, respectively, indicating their superior degradation. Notably, SNUT-35-Zn demonstrated exceptional detection capabilities for aromatic compounds, such as aniline and nitrobenzene, at lower concentration range without interference from other components. The detection limits for these two small molecules were found to be 0.430 and 0.431 μM, respectively. Additionally, both MOFs exhibited larger transient photocurrents and lower impedance in electrochemical measurements. The results suggested that the photocatalytic activities of MOF are influenced by their three-dimensional structures, which facilitate electrons passing due to the inherent semiconductor properties.

Dual Ligand Strategy for Efficient and Stable Ag–In–Ga–S Aqueous Quantum Dots

AbstractIn recent years, Ag−In−Ga−S (AIGS) quaternary quantum dots (QDs) have garnered significant attention as a novel class of environmentally friendly and non‐toxic QDs. However, the hydrothermal synthesis method for aqueous QDs has been plagued by issues such as inconsistent size, subpar crystallinity, and low photoluminescence quantum yield (PLQY). Herein, we developed a dual ligand strategy based on the hard and soft acids and bases (HSAB) theory to synthesize aqueous AIGS QDs with an impressive PLQY of up to 64.3 %, currently the highest value among hydrothermal‐synthesized uncoated I–III–VI QDs. The QDs exhibit better crystallinity, narrow size distribution (3.07±0.31 nm), and remarkable stability. The mechanism underlying this dual ligand strategy was further elucidated, shedding light on the distinct influences of different ligands on the growth of QDs. The high PLQY contributes to the further application of aqueous AIGS QDs in luminescent displays and the field of biology. Meanwhile, this ligand strategy has broad reference significance for efficient preparation of other water‐soluble QDs.

Achiral and chiral ligands synergistically harness chiral self-assembly of inorganics.

Chiral structures and functions are essential natural components in biominerals and biological crystals. Chiral molecules direct inorganics through chiral growth of facets or screw dislocation of crystal clusters. As chirality promoters, they initiate an asymmetric hierarchical self-assembly in a quasi-thermodynamic steady state. However, achieving chiral assembly requires a delicate balance between intricate interactions. This complexity causes the roles of achiral-chiral and inorganic components in crystallization to remain ambiguous. Here, we elucidate a definitive mechanism using an achiral-chiral ligand strategy to assemble inorganics into hierarchical, self-organized superstructures. Achiral ligands cluster inorganic building blocks, while chiral ligands impart chiral rotation. Achiral and chiral ligands can flexibly modulate the chirality of superstructures by fully using their competition in coordination chemistry. This dual-ligand strategy offers a versatile framework for engineering chiroptical nanomaterials tailored to optical devices and metamaterials with optical activities across a broad wavelength range, with applications in imaging, detection, catalysis, and sensing.

A Thorium(IV) metallacyclopropyne complex

Actinide metallacyclic chemistry has been of interest due to its involvement in various chemical processes. However, fundamental understanding on the key species, actinide metallacyclic complexes, is limited to metallacyclopropenes whereas little is known about the actinide metallacyclopropynes presumably due to their unusual high reactivity. Herein, we report the preparation of a thorium metallacyclopropyne complex (η2-C ≡ C)ThCl3– in the gas phase by using electrospray ionization mass spectrometry, and it is generated via a single-ligand strategy through sequential losses of CO2 and HCl from the monopropynoate precursor (HC ≡ CCO2)ThCl4– upon collision-induced dissociation. Alternatively, the dual-ligand strategy involving consecutive losses of two CO2 and one C2H2 from the dipropynoate precursor (HC ≡ CCO2)2ThCl3– works as well. According to the reactivity experiments and theoretical calculations, (η2-C ≡ C)ThCl3– possesses a dianionic ligand C22– coordinated to the Th(IV) center in a side-on fashion. Further bonding analysis demonstrates the presence of a triple bond between the two C atoms, and the Th 5 f orbitals are significantly involved in the Th-(C ≡ C) bonding. A Th metallacyclopropyne structure is thus established for (η2-C ≡ C)ThCl3–.

Three coordination polymers based on 4,4′-bis(2-methylimidazol-1-yl)diphenyl ether: Synthesis, structure and selective fluorescent sensing properties

Three CPs [Zn2(PDA)2(BMIOPE)2·3H2O]n (1), [Co(Br-BDC)(BMIOPE)]n (2) and [Co(MIP)(BMIOPE)]n (3) were synthesized by solvothermal method based on dual-ligand strategy (H2PDA, Br-H2BDC, BMIOPE and H2MIP are 1,3-phenylenediacetic acid, 5-bromo-isophthalic acid, 4,4′-bis(2-methylimidazol-1-yl)diphenyl ether and 5-methylisophthalic acid, respectively). Complexes 1 and 3 exhibit twofold parallel interwoven sql nets. Complex 2 is 2D layer structure. The luminescence property investigations showed that complexes 1–3 could act as multi-responsive fluorescent sensors to detect UO22+, Cr2O72− and CrO42− and nitrofurantoin (NFT) through fluorescence turn-off process, presenting excellent sensitivity and selectivity. Finally, the possible fluorescent quenching mechanisms of complexes 1–3 toward the above pollutants are also further investigated by employing spectroscopic methods and quantum chemical calculations. The fluorescence lifetime measurements manifest the mechanism of fluorescence quenching is static quenching process.

Formation and Structure of Gas-Phase Lanthanide(III) Cyanobenzyne Complex (η2-4-CNC6H3)LnCl2-, Obtained via Both the Single- and Dual-Ligand Strategies.

The lanthanide(III) cyanobenzyne complexes (η2-4-CNC6H3)LnCl2- (Ln = La-Lu except Eu; Pm was not examined) were generated in the gas phase using an electrospray ionization mass spectrometry coupled with collision-induced dissociation (CID) technique. For all lanthanides except Sm, Eu, and Yb, (4-CNC6H3)LnCl2- can be generated either via a single-ligand strategy through consecutive CO2 and HCl losses of (4-CNC6H4CO2)LnCl3- or via a dual-ligand strategy through successive CO2/C6H5CN or 4-CNC6H4CO2H and CO2 losses of (4-CNC6H4CO2)2LnCl2-. For Sm and Yb, although only reduction products LnCl3- were formed upon CID of (4-CNC6H4CO2)LnCl3-, (4-CNC6H3)LnCl2- were obtained via the dual-ligand strategy without the appearances of other products. CID of (4-CNC6H4CO2)EuCl3- and (4-CNC6H4CO2)2EuCl2- gave EuCl3- and the cyanophenyl complex (4-CNC6H4)EuCl2-, respectively, in both of which the +III oxidation state of Eu was reduced to +II. Density functional theory (DFT) calculations reveal that (4-CNC6H3)LnCl2- are formally described as Ln(III) cyanobenzyne complexes, (η2-4-CNC6H3)LnCl2-, with the dianionic cyanobenzyne ligand (4-CNC6H32-) coordinating to the Ln(III) centers through two Ln-C σ bonds, which is in accordance with their reactivities toward water. Benzyne and substituted benzyne complexes (XC6H3)LuCl2- (X = H, 3-CN, 4-F, 4-Cl, and 4-CH3) were also synthesized in the gas phase via the single- and dual-ligand strategies.

Specific Discrimination Polymerization for Highly Isotactic Polyesters Synthesis.

Isotactic polymers have emerged with unique and excellent properties in material sciences. Specific discrimination polymerization provides an ideal pathway to achieve highly isotactic polymers from their racemic monomers, which is of great significance and a challenge in polymeric chemistry. Although an enantioselective catalyst-mediated asymmetric kinetic resolution polymerization (AKRP) process makes it possible, a general and well-defined strategy for catalyst design is still rarely reported. Here, based on a novel dual-ligand strategy, a new type of chiral (BisSalen)Al complex with high enantioselectivity has been described, in which perfect AKRP of racemic phenethylglycolide (Pegl) is achieved for the first time. The more confined asymmetric microenvironment formed by a dual ligand is the key to improve the enantioselectivity of the original catalyst. To illustrate the generality of this strategy, a series of (BisSalen)Al complexes with homo- or heterodual ligands were designed for the AKRP of Pegl.

Pure separation of acetylene based on a sulfonic acid and amino group functionalized Zn-MOF.

The dual-ligand strategy was employed to synthesize a new microporous material, [Zn3(SNDC)(AmTAZ)3(H2O)]·H2O·CH3CN (1), incorporating sulfonic acid and amino groups for enhancing gas adsorption and separation. The activated 1 (named 1a) exhibited selective adsorption of acetylene over carbon dioxide and methane. Hence, the dual-ligand strategy optimized the pore environment and provided an effective approach for pure separation of gases.

A mechanochemically synthesized Schiff-base engineered 2D mixed-linker MOF for CO2 capture and cationic dye removal.

Developing synthetic strategies for smart materials for the adsorption and separation of toxic chemicals is of great importance. Metal-organic frameworks (MOFs) have been proven to be outstanding adsorbent materials that possess excellent pollutant removal performances in wastewater treatment, including dye recycling. In this work, a neutral Cd(II) based 2D framework with a dual ligand strategy involving -OH functionalized 5-hydroxyisophthalic acid (5-OH-H2IPA) and the amide decorated Schiff base ligand (E)-N'-(pyridin-4-ylmethylene)isonicotinohydrazide (L) has been synthesized by different synthetic routes and characterized by various analytical methods. Thus, crystals of {[Cd(5-OH-IPA)(L)]·CH3OH}n synthesized via diffusion (ADES-7D) and the phase pure bulk product synthesized by conventional reflux (ADES-7C) and the mechanochemical grinding method (ADES-7M) have been established using PXRD data of the respective product showing identical simulated SXRD data to those of ADES-7D. The mechanochemically synthesized ADES-7M possesses a better surface area and CO2 adsorption capability compared to ADES-7C, which is also supported by electron microscopy and particle size measurements. Furthermore, ADES-7 can be used as an efficient adsorbent material for the reversible, selective adsorption (42-99%) and separation of the cationic dyes malachite green (MG), methyl violet (MV), methylene blue (MB), and rhodamine B (RhB) from the mixture of cationic/anionic dyes (methyl orange (MO) and bromocresol green (BCG)) in the aqueous phase. Specifically, ADES-7M possesses better dye capture capability compared to ADES-7C, even in the case of the bigger dye RhB with adsorption differences of 2.38 to 1.01 mg g-1, respectively. The dye adsorption kinetics follows pseudo-second-order kinetics, and the dye adsorption isotherm fits well with the Langmuir/Freundlich adsorption isotherm models. The probable mechanism of adsorption involving the supramolecular interaction between the host MOF and the guest dye has also been proposed.

Eu3+-MOF fluorescence sensor based on a dual-ligand strategy for visualised detection of an anthrax biomarker 2,6-pyridine dicarboxylic acid

A dual-ligand ratiometric fluorescence sensor based on lanthanide–metal–organic frameworks was successfully synthesised for the sensitive and convenient detection of DPA.

Dual-Ligand Strategy for the Design and Construction of a Cd-Zn Heterometallic Metal-Organic Framework by One-Pot Synthesis as a Heterogeneous Catalyst for the Epoxidation Reaction of Olefins.

The use of metal-organic frameworks (MOFs) as catalysts is reported in various industrial applications. In contrast to monometallic MOFs, heterometallic MOFs with mixed organic ligands showed enhanced catalytic properties. The catalytic properties of heterometallic MOFs can be enhanced by generating defects and the synergistic effect between the two heterometals at secondary building units. By using a solvothermal technique, a Cd-Zn heterometallic MOF with a new morphology, [Cd2Zn(DPTTZ)0.5(OBA)3(H2O)(HCOOH)] (IUST-4) [DPTTZ = 2,5-di(4-pyridyl)thiazolo[5,4-d]thiazole, OBA = 4,4'-oxybis(benzoic acid)], was synthesized via a mixed-ligand strategy and characterized by single-crystal and powder X-ray diffraction, Fourier transform infrared spectroscopy, elemental analysis, and thermogravimetric analysis. X-ray crystallographic analysis showed that IUST-4 is a neutral 3D metal-organic framework crystallized in the monoclinic system with space group C2/c. In this study, the catalytic properties of IUST-4 for the epoxidation of cyclooctene were investigated. IUST-4 was selected as the optimal catalyst for epoxy product production due to its high selectivity and yield. Moreover, the catalytic performance of IUST-4 was maintained despite five recycling cycles without significant degradation. The epoxidation of cyclooctene with IUST-4 has several advantages, including good selectivity, easy recovery, and short-time reaction.

Dual-Ligand Strategy to Construct Metal Organic Gel Catalyst with the Optimized Electronic Structure for High-Efficiency Overall Water Splitting and Flexible Metal-Air Battery.

Non-noble metal catalysts are known for their efficient catalytic performance for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). Metal organic gels (MOGs) can be considered as a promising electrocatalyst owing to the diverse physicochemical properties but usually suffer from its poor electrical conductivity and catalytic stability. Here, a FeCo-MOG is constructed with considerable trifunctional activity. The optimal P-CoFe-H3 prepared by using phytic acid (PA) and 2,4,6-Tris[(p-carboxyphenyl)amino]-1,3,5-triazine benzoic acid (H3TATAB) as dual ligands), exhibits outstanding ORR, OER, and HER activities as well as stability, exceeding most of state-of-the-art catalysts. As expected, the flexible Zn-air battery applied with P-CoFe-H3 as air cathode displays considerable power density, discharge voltage plateau, and cycling stability. Impressively, it is also capable of driving the overall water-splitting device by applying the P-CoFe-H3 as anode and cathode. Furthermore, theoretical calculations reveal that dual ligands can optimize the coordination environment and charge density of active sites, thereby reducing the absorption energy of intermediate species and boosting the catalytic performance. This work endows the dual-ligands coordination strategy with great potentiality for MOGs-based electrocatalysts in energy conversion devices.

Twofold interpenetrated 3D Cd(ii) complex: Crystal structure and luminescent property

Abstract A novel Cd(II) compound, namely [Cd6(TCA)4(4-bpmh)(DMA)2(H2O)2] n ·4n(H2O) (denoted as 1, H3TCA = 4,4′,4″-tricarboxytriphenylamine, 4-bpmh = N,N-bis(pyridin-4-ylmethylene)hydrazine, and DMA = N,N′-dimethylacetamine), has been solvothermally prepared via a dual-ligand strategy that employs two organic ligands to fulfill different functions. The solid of compound 1 shows blue luminescence at room temperature.

Synthesis of Fe Atom-Doped Monodisperse Co2P Nanorods with a Dual-Ligand Strategy for Excellent Electrocatalytic Hydrogen Evolution Performance.

Cobalt phosphide has been widely used in various catalytic reactions due to its excellent catalytic activity and stability. In contrast to the conventional synthesis of Co2P nanorods using expensive and toxic trioctylphosphine (TOP), this study employs a dual-ligand strategy to prepare iron-atom-doped monodisperse Co2P nanorods. The strategy involves the use of triphenylphosphite (TPOP) as a cost-effective and relatively less toxic strong ligand, alongside hexadecylamine (HDA) as a weaker ligand. The resultant atom-doped Co2P nanorods exhibited a large aspect ratio, providing a plentiful supply of active sites for electrocatalytic hydrogen evolution. In both alkaline and acidic electrolytes, achieving a current density of 10 mA cm-2 required overpotentials of 91 and 141 mV, respectively, with the optimal Co:Fe molar ratio of 1:0.2. The introduction of Fe atoms through doping increased the electron density at the Co atom sites, thereby enhancing H adsorption. This research offers a cost-effective and relatively low-toxicity method for the controlled fabrication of monodisperse transition-metal phosphide nanorods, enabling efficient catalytic reactions.

Dual-Functional Eu-Metal-Organic Framework with Ratiometric Fluorescent Broad-Spectrum Sensing of Benzophenone-like Ultraviolet Filters and High Proton Conduction.

The construction of attractive dual-functional lanthanide-based metal-organic frameworks (Ln-MOFs) with ratiometric fluorescent detection and proton conductivity is significant and challenging. Herein, a three-dimensional (3D) Eu-MOF, namely, [Eu4(HL)2(SBA)4(H2O)6]·9H2O, has been hydrothermally synthesized with a dual-ligand strategy, using (4-carboxypiperidyl)-N-methylenephosphonic acid (H3L = H2O3PCH2-NC5H9-COOH) and 4-sulfobenzoic acid monopotassium salt (KHSBA = KO3SC6H4COOH) as organic linkers. Eu-MOF showed ratiometric fluorescent broad-spectrum sensing of benzophenone-like ultraviolet filters (BP-like UVFs) with satisfactory sensitivity, selectivity, and low limits of detection in water/ethanol (1:1, v/v) solutions and real urine systems. A portable test paper was prepared for the convenience of actual detection. The potential sensing mechanisms were thoroughly analyzed by diversified experiments. The synergistic effect of the forbidden energy transfer from the ligand to Eu3+, the internal filtration effect (IFE), the formation of a complex, and weak interactions between the KHSBA ligand and BP-like UVFs is responsible for the ratiometric sensing effect. Meanwhile, Eu-MOF displayed relatively high proton conductivity of 2.60 × 10-4 S cm-1 at 368 K and 95% relative humidity (RH), making it a potential material for proton conduction. This work provides valuable guidance for the facile and effective design and construction of multifunctional Ln-MOFs with promising performance.

Dual-ligand two-dimensional terbium-organic frameworks nanosheets for ratiometric fluorescence detection of phosphate

Here, we reported a ratiometric fluorescence strategy for the detection of phosphate (Pi) in artificial wetland water. The strategy was based on dual-ligand two-dimensional terbium-organic frameworks nanosheets (2D Tb-NB MOFs). 2D Tb-NB MOFs were prepared through blending 5-boronoisophthalic acid (5-bop), 2-aminoterephthalic acid (NH2-BDC) and Tb3+ ions at room temperature in the presence of triethylamine (TEA). The dual-ligand strategy realized dual emission originated from ligand NH2-BDC and Tb3+ ions at 424 and 544 nm, respectively. Pi could compete with ligands to coordinate Tb3+ due to the strong binding ability between Pi and Tb3+, resulting in structural destruction of 2D Tb-NB MOFs, so static quenching and antenna effect between ligands and metal ions were interrupted, and emission at 424 nm was enhanced and emission at 544 nm was weakened. This novel probe had excellent linearity with Pi concentrations from 1 to 50 μmol/L; the detection limit was 0.16 μmol/L. This work revealed that mixed ligands improved sensing efficiency of MOFs by enhancing the sensitivity of the coordination between the analyte and MOFs.

Construction of two new Zn(II)-based coordination polymers as photocatalyst for degradation of antibiotic

Two new Zn(II)-based coordination polymers (CPs), namely, [Zn2(L)2(2,2′-bipy)2] (1) and [Zn(L)(bib)0.5] (2) (H2L =4,4′- (1,2-phenlenebis(methyleneoxy)dibenzoic acid, 2,2′-bipy = 2,2′-bipyridine and bib=1,4-bis(1-imidazoly)benzene) were constructed by using a dual ligand strategy. The CPs are characterized by single X-ray diffraction, FT-IR, TGA and UV–visible spectroscopy. 1 exhibits 1D supramolecular chain was built by the hydrogen bond interactions between adjacent chains. 2 has 3D supramolecular network due to a coordinate bond. The photocatalytic degradation properties of the two CPs are investigated against different antibiotics like Tetracycline (TCY), metronidazole (MDZ), sulfamethazine (SMZ), nitrofurantoin (NFT), chloramphenicol (CAP), dinitrazole (DTZ), thiamphenicol (THI) and nitrofurazone (NZF). The degradation efficiency of MDZ by 1 was very high compared to other antibiotic or 2. Moreover, the possible photodegradation mechanism was proposed and explored by a radical tapping experiment.

Dual-Ligand Strategy for the Preparation of Gas-Phase Uranyl(VI) Benzyne Complexes from Uranyl(VI) Benzoates.

The uranyl(VI) benzyne complex (η2-C6H4)UO2Cl- was prepared in the gas phase by electrospray ionization mass spectrometry coupled with collision-induced dissociation. It was formed via a dual-ligand strategy that requires the elimination of benzoic acid or benzene/CO2 from the uranyl dibenzoate precursor (C6H5CO2)2UO2Cl-. This contrasts the known strategy for the formation of gas-phase benzyne complexes that would result from CO2/HCl elimination from (C6H5CO2)UO2Cl2-, during which only one benzoate ligand is involved. Such dual-ligand strategy can be extended to the preparation of a series of methyl- and halo-substituted benzyne complexes of uranyl(VI). Density functional theory calculations at the B3LYP level reveal that the benzyne complex (η2-C6H4)UO2Cl- features a metallacyclopropene structure with the C6H42- ligand coordinated to uranium(VI) through two polarized U-Cbenzyne σ bonds, in accordance with the reactivity test toward water. Dehydrochlorination of the benzyne complex (η2-C6H4)UO2Cl- from (C6H5)UO2Cl2- that originates from decarboxylation of (C6H5CO2)UO2Cl2- with a single benzoate ligand is neither kinetically nor thermodynamically favorable than simple C6H5 radical loss to give UVO2Cl2-. This arises from the presence of an accessible V oxidation state for uranium and accounts for the necessity for the dual-ligand strategy in the preparation of uranyl(VI) benzyne complexes from uranyl benzoate precursors.

MOF-derived Fe–N–C electrocatalyst via a dual ligand strategy for efficient oxygen reduction in acidic media

A metal–organic-framework based dual ligand strategy is proposed to develop high-performance acid ORR Fe–N–C electrocatalyst via the synergistic effect between in situ Zn evaporation and ligand-manipulated pyrolysis.

A new dual-ligand DUT-52-type metal-organic framework for ratiometric luminescence detection of aqueous-phase Cu2+ and Cr2O72.

Metal-organic frameworks (MOFs) are a unique class of multifunctional hybrid crystals that have been successfully utilized in diverse ranges of applications. However, since MOFs are prone to aqueous degradation, the development of stable luminescent MOF platforms in aqueous media is still a huge challenge. Here, a novel dual-ligand Eu3+/DUT-52-COOH composite is prepared based on the luminescent DUT-52 prototype structure via a dual-ligand strategy and a post-synthetic modification (PSM) method. The functionalized Eu3+/DUT-52-COOH material exhibits dual emission and good photothermal stability in aqueous media. Thus, Eu3+/DUT-52-COOH is developed as a ratiometric luminescent sensor to achieve highly selective and sensitive detection of Cu2+ and Cr2O72- in aqueous solutions and has a low detection limit of 3.43 μM and 25.7 nM, respectively. This work is one of the few cases of detecting Cu2+ and Cr2O72- in aqueous media based on a DUT-52, and the detection signals can be observed by the bare eye without using sophisticated analytical instruments. The possible sensing mechanism is discussed in detail. The results obtained in this project may provide broad prospects for developing smart sensing systems to accomplish highly efficient, easily operable and quantitative intelligent recognition of Cu2+ and Cr2O72-.