Bimetallic Coordination Research Articles

A Class of Heptaphyrins with NIR Absorption Modulated by Metal Coordination and Nucleophilic Substitution.

The intensive interest in expanded porphyrins can be attributed to their appealing photoelectric and coordination behavior. In this work, an N-confused heptaphyrin 1 was synthesized by an acid-catalyzed [3+4] condensation reaction. The introduction of an N-confused pyrrolic unit into the heptaphyrin macrocycle led to the formation of a figure-eight-like conformation with nonsymmetrical "NNNN" and "NNNC" coordination cavities employable for bimetallic coordination. As a result, chelation of 1 with Zn(II) and Cu(II) afforded mono-Zn(II) complex 2 and bis-Cu(II) complex 3, respectively, with the metal atoms exhibiting distorted square-planar geometries. In complex 3, an oxygen atom is attached to the α-C atom of N-confused pyrrole D, and thus the N and C atoms of ring D participate in coordination within the two cavities. Interestingly, treatment of 1 with Cs2CO3 in MeOH resulted in regioselective substitution of all the seven para-F atoms in the meso-C6F5 groups as well as the α-H of ring D by eight methoxy moieties. Complex 3 displays a red-shifted absorption band edge of ca. 2200 nm, compared to that of ca. 1600 nm observed for 1. This work provides an example of incorporating an N-confused pyrrole to construct expanded porphyrins with distinctive coordination behavior and tunable NIR absorption.

Copper-Nickel Bimetallic Coordination Polymers as Precursors for New Cu-Ni Oxide Electrocatalyst for OER

Copper-Nickel Bimetallic Coordination Polymers as Precursors for New Cu-Ni Oxide Electrocatalyst for OER

Surface Oxygen Defect Engineering of A2B2O7 Pyrochlore Semiconductors Boosts the Electrocatalytic Reduction of CO2-to-HCOOH.

The electrocatalytic conversion of inert CO2 to value-added chemical fuels powered by renewable energy is one of the benchmark approaches to address excessive carbon emissions and achieve carbon-neutral energy restructuring. However, the adsorption/activation of supersymmetric CO2 is facing insurmountable challenges that constrain its industrial-scale applications. Here, this theory-guided study confronts these challenges by leveraging the synergies of bimetallic sites and defect engineering, where pyrochlore-type semiconductor A2B2O7 is employed as research platform and the conversion of CO2-to-HCOOH as the model reaction. Specifically, defect engineering intensified greatly the chemisorption-induced CO2 polarization via the bimetallic coordination, thermodynamically beneficial to the HCOOH production via the *HCO2 intermediate. The optimal V-BSO-430 electrocatalyst with abundant surface oxygen vacancies achieved a superior HCOOH yield of 116.7mmol h-1 cm-2 at -1.2 VRHE, rivalling the incumbent similar reaction systems. Furthermore, the unique catalytic unit featured with a Bi1-Sn-Bi2 triangular structure, which is reconstructed by defect engineering, and altered the pathway of CO2 adsorption and activation to allow the preferential affinity of the suspended O atom in *HCO2 to H. As a result, V-BSO-430 gave an impressive FEHCOOH of 93% at -1.0 VRHE. This study held promises for inspiring the exploration of bimetallic materials from the massive semiconductor database.

Stabilizing Ni2+ in Hollow Nano MOF/Polymetallic Phosphides Composites for Enhanced Electrochemical Performance in 3D-Printed Micro-Supercapacitors.

Polymetallic phosphides exhibit favorable conductivities. A reasonable design of nano-metal-organic frame (MOF) composite morphologies and in situ introduction of polymetallic phosphides into the framework can effectively improve electrolyte penetration and rapid electron transfer. To address existing challenges, Ni, with a strong coordination ability with N, is introduced to partially replace Co in nano-Co-MOF composite. The hollow nanostructure is stabilized through CoNi bimetallic coordination and low-temperature controllable polymetallic phosphide generation rate. The Ni, Co, and P atoms, generated during reduction, effectively enhance electron transfer rate within the framework. X-ray absorption fine structure (XAFS) characterization results further confirm the existence of Ni-N, Ni-Ni, and Co-Co structures in the nanocomposite. The changes in each component during the charge-discharge process of the electrochemical reactions are investigated using in situ X-ray diffraction (XRD). Theoretical calculations further confirm that P can effectively improve conductivity. VZNPGC//MXene MSCs, constructed with active materials derived from the hollow nano MOF composites synthesized through the Ni2+ stabilization strategy, demonstrate a specific capacitance of 1184 mF cm-2, along with an energy density of 236.75 µWh cm-2 (power density of 0.14 mW cm-2). This approach introduces a new direction for the synthesis of highly conductive nano-MOF composites.

Visible light photocatalytic performance of Co/Ag bimetallic coordination polymer catalysts designed from hard and soft acid-base theory

Heterometallic coordination polymers have promising applications in photocatalysis, and the design and selection of suitable organic ligands and coordination metals is the key to improve the catalytic activity of polymer photocatalysts. Herein, a novel Co/Ag bimetallic coordination photocatalyst, designed based on the hard and soft acid-base (HSAB) theory, has been successfully prepared by a stepwise method with Ag-S coordination as the main component and Co-N/Co-S as the complementary component. The obtained Co/Ag photocatalyst demonstrates excellent performance in the photocatalytic degradation (visible light) of halogenated phenolic pollutants. Degradation of 10 ppm of 4-chlorophenol could reach 100 % in 4 h, and 70 % degradation of 4-fluorophenol, which is even more difficult to degrade, could also be achieved. In addition, hydrogen production experiments conducted under visible light irradiation showed that the hydrogen production could reach 36.95 μmol h−1 g−1 for 6 h, which strongly demonstrated the excellent reduction ability of Co/Ag photocatalysts. The photocatalyst exhibits enhanced photocatalytic activity which is ascribed to the formation of Ag-S and Co-N/Co-S coordination, which greatly increases the charge density and facilitates charge transfer. Thus, the photogenerated electrons can induce both the conversion of O2 to •O2- for oxidation reactions, as well as the direct attack of the C-Cl bond for reduction reactions. This study demonstrates the successful design of the synergistic Co/Ag bimetallic coordination photocatalysts based on the HSAB theory, thereby offering a promising research avenue for the fabrication of heterometallic coordination photocatalysts.

MRI-guided cell membrane-camouflaged bimetallic coordination nanoplatform for combined tumor phototherapy

Nanotechnology for tumor diagnosis and optical therapy has attracted widespread interest due to its low toxicity and convenience but is severely limited due to uncontrollable tumor targeting. In this work, homologous cancer cell membrane-camouflaged multifunctional hybrid metal coordination nanoparticles (DRu/Gd@CM) were prepared for MRI-guided photodynamic therapy (PDT) and photothermal therapy (PTT) of tumors. Bimetallic coordination nanoparticles are composed of three functional modules: dopamine, Ru(dcbpy)3Cl2 and GdCl3, which are connected through 1,4-Bis[(1H-imidazole-1-yl)methyl]benzene (BIX). Their morphology can be easily controlled by adjusting the ratio of precursors. Optimistically, the intrinsic properties of the precursors, including the photothermal properties of polydopamine (PDA), the magnetic resonance (MR) response of Gd3+, and the singlet oxygen generation of Ru(dcbpy)3Cl2, are well preserved in the hybrid metal nanoparticles. Furthermore, the targeting of homologous cancer cell membranes enables these coordinated nanoparticles to precisely target tumor cells. The MR imaging capabilities and the combination of PDT and PTT were demonstrated in in vitro experiments. In addition, in vivo experiments indicated that the nanoplatform showed excellent tumor accumulation and therapeutic effects on mice with subcutaneous tumors, and could effectively eliminate tumors within 14 days. Therefore, it expanded the new horizon for the preparation of modular nanoplatform and imaging-guided optical therapy of tumors.

Tumor Microenvironment-Regulating Two-Photon Probe Based on Bimetallic Post-Coordinated MOF Facilitating the Dual-Modal and Deep Imaging-Guided Synergistic Therapies.

The intricate tumor microenvironment (TME) always brings about unsatisfactory therapeutic effects for treatments, although nanomedicines have been demonstrated to be highly beneficial for synergistic therapies to avoid the side effects caused by the complexity and heterogeneity of cancer. Developing nanotheranostics with the functionalities of both synergistic therapies and TME regulation is a good strategy but is still in its infancy. Herein, an "all-in-one" nanoplatform for integrated diagnosis and treatment, namely, Carrier@ICG@DOX@FA (CIDF), is constructed. Benefiting from the bimetallic coordination of Eu3+-HTHA (4,4,4-trifluoro-1-(9-hexylcarbazol-3-yl)-1,3-butanedione) and Fe3+ with the ligands in UiO-67, CIDF can simultaneously achieve two-photon fluorescence imaging, fluorescent lifetime imaging in deep tumors, and regulation of TME. Owing to its porosity, CIDF can encapsulate indocyanine green as photosensitizers and doxorubicin as chemotherapeutic agent, further realizing light-controlled drug release. Moreover, CIDF exhibited good biocompatibility and tumor targeting by coating with folic-acid-modified polymers. Both in vitro and in vivo experiments demonstrate the excellent therapeutic efficacy of CIDF through dual-modal-imaging-guided synergistic photothermal-, photodynamic-, and chemotherapy. CIDF provides a new paradigm for the construction of TME-regulated synergistic nanotheranostics and realizes the complete elimination of tumors without recurrence.

Bimetallic Coordination Polymers: Synthesis and Applications in Biosensing and Biomedicine.

Bimetallic coordination polymers (CPs) have two different metal ions as connecting nodes in their polymer structure. The synthesis methods of bimetallic CPs are mainly categorized into the one-pot method and post-synthesis modifications according to various needs. Compared with monometallic CPs, bimetallic CPs have synergistic effects and excellent properties, such as higher gas adsorption rate, more efficient catalytic properties, stronger luminescent properties, and more stable loading platforms, which have been widely applied in the fields of gas adsorption, catalysis, energy storage as well as conversion, and biosensing. In recent years, the study of bimetallic CPs synergized with cancer drugs and functional nanomaterials for the therapy of cancer has increasingly attracted the attention of scientists. This review presents the research progress of bimetallic CPs in biosensing and biomedicine in the last five years and provides a perspective for their future development.

Retraction Note: Two New Alkali/Cadmium Bimetallic Coordination Polymers: Luminescent Properties and Cancer Prevention by Regulating the Interaction between High Mobility Group Protein B1 and Immune Cells

Retraction Note: Two New Alkali/Cadmium Bimetallic Coordination Polymers: Luminescent Properties and Cancer Prevention by Regulating the Interaction between High Mobility Group Protein B1 and Immune Cells

Geminal bimetallic coordination of a carbone to main-group and transition metals.

The non-bonding carbone lone pair in geometrically-constrained antimony and bismuth carbodiphosphorane complexes readily complexed AuCl to afford rare examples of geminal bimetallic carbone coordination featuring a main-group metal.

Construction of cobalt–nickel bimetallic coordination polymers and their catalytic thermal decomposition of ammonium perchlorate

The addition of a catalyst to ammonium perchlorate (AP) can effectively improve its thermal decomposition properties. The heterobimetallic complex Ni-Co-pzdc (2,3-pyrazinedicarboxylic acid) was synthesized via in situ substitution, and the N-doped Ni-Co-pzdc derivative was prepared by using it as a sacrificial template. A series of characterization tools were used to investigate the morphological and structural features of the resulting materials, and the thermal decomposition behaviors of the two products were investigated by homogeneous mixing with AP, respectively, and the activation energies were calculated by using Kissinger, Kissinger-Akahira-Sunose (KAS), and Flynn-Wall-Ozawa (FWO), and the results showed that both substances possessed excellent catalytic activities.

Review of Carbon Support Coordination Environments for Single Metal Atom Electrocatalysts (SACS).

This topical review focuses on the distinct role of carbon support coordination environment of single-atom catalysts (SACs) for electrocatalysis. The article begins with an overview of atomic coordination configurations in SACs, including a discussion of the advanced characterization techniques and simulation used for understanding the active sites. A summary of key electrocatalysis applications is then provided. These processes are oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), nitrogen reduction reaction (NRR), and carbon dioxide reduction reaction (CO2 RR). The review then shifts to modulation of the metal atom-carbon coordination environments, focusing on nitrogen and other non-metal coordination through modulation at the first coordination shell and modulation in the second and higher coordination shells. Representative case studies are provided, starting with the classic four-nitrogen-coordinated single metal atom (MN4 ) based SACs. Bimetallic coordination models including homo-paired and hetero-paired active sites are also discussed, being categorized as emerging approaches. The theme of the discussions is the correlation between synthesis methods for selective doping, the carbon structure-electron configuration changes associated with the doping, the analytical techniques used to ascertain these changes, and the resultant electrocatalysis performance. Critical unanswered questions as well as promising underexplored research directions are identified.

A Fe-Ni-MOF-74@bamboo photothermal evaporator for efficient solar steam generation

Solar-driven interfacial steam generation is considered as a promising technology to solve the shortage of fresh water resources by using inexhaustible solar energy. In this field, the challenge comes from the design of an interfacial evaporator with high performance in photothermal conversion, water activation (low evaporation enthalpy) and water delivery ability. Herein, a composite evaporator was prepared by in-situ composition of bamboo and Fe-Ni-MOF-74 and subsequently simple carbonization. In this evaporator, bamboo ensures that water quickly reaches the evaporation interface, and rich hydrophilic groups have the function of activating water molecules. Fe-Ni-MOF-74 enhances photothermal effect due to bimetallic coordination. In addition, the hydrophilic feature and the pore structure strengthen the water activation and water absorption capacity. Meanwhile, carbonization under mild conditions compensates for the light absorption. As an outcome, the evaporator achieves high evaporation rate (3.61 kg m−2 h−1), high solar-vapor conversion efficiency (153 %), low evaporation enthalpy (1.517 kJ g−1), good stability in saline water and antibacterial function. Furthermore, both seawater and wastewater purified by the evaporator comply with drinking water standards. In the outdoor experiment, the evaporator can collect water of 4.01 kg m−2 during one daylight. The result highlights great potential of bamboo and MOF composite evaporator for producing fresh water using solar energy.

Regulation of Bimetallic Coordination Centers in MOF Catalyst for Electrochemical CO2 Reduction to Formate.

Electrocatalytic reduction of CO2 to valuable chemicals can alleviate the energy crisis, and solve the greenhouse effect. The key is to develop non-noble metal electrocatalysts with high activity, selectivity, and stability. Herein, bimetallic metal organic frameworks (MOFs) materials (BiZn-MOF, BiSn-MOF, and BiIn-MOF) were constructed by coordinating the metals Zn, In, Sn, and Bi with the organic ligand 3-amino-1H-1,2,4-triazole-5-carboxylic acid (H2atzc) through a rapid microwave synthesis approach. The coordination centers in bimetallic MOF catalyst were regulated to optimize the catalytic performance for electrochemical CO2 reduction reaction (CO2RR). The optimized catalyst BiZn-MOF exhibited higher catalytic activity than those of Bi-MOF, BiSn-MOF, and BiIn-MOF. BiZn-MOF exhibited a higher selectivity for formate production with a Faradic efficiency (FE = 92%) at a potential of -0.9 V (vs. RHE, reversible hydrogen electrode) with a current density of 13 mA cm-2. The current density maintained continuous electrolysis for 13 h. The electrochemical conversion of CO2 to formate mainly follows the *OCHO pathway. The good catalytic performance of BiZn-MOF may be attributed to the Bi-Zn bimetallic coordination centers in the MOF, which can reduce the binding energies of the reaction intermediates by tuning the electronic structure and atomic arrangement. This study provides a feasible strategy for performance optimization of bismuth-based catalysts.

Abundant Surface Defects in Cobalt Hydroxides/Oxyhydroxides Induced by Zinc Species Facilitate Water Oxidation.

The complex process of the anodic oxygen evolution reaction (OER) severely hinders overall water splitting, which further limits the large-scale production and application of hydrogen energy. In this work, one type of bimetallic coordination polymer of ZnCoBTC using the MOF-on-MOF strategy has been synthesized where both Co(II) and Zn(II) cations exhibit the same coordination environment. By applying an electric potential, the predesigned bimetallic MOF precursor can be conveniently degraded into CoOxHy as an active species for efficient OER. Owing to the dissolution of ZnOxHy species, in situ formed disordered defects on the external surface of the catalyst increase the specific surface area as well as expose abundant active materials. Therefore, the ZnCoOxHy nanosheet shows excellent OER performance and reaches an overpotential of only 334 mV at 10 mA cm-2 with a Tafel slope of 66.4 mV dec-1, indicating fast reaction kinetics. The results demonstrate that metals with the same coordination environment can undergo in situ replacement or secondary growth on the pristine MOF, and they can be electrochemically degraded into highly efficient catalysts for future energy applications.

Comparison of Eco-friendly Ti-M Bimetallic Coordination Catalysts and Commercial Monometallic Sb- or Ti-Based Catalysts for the Synthesis of Poly(ethylene-co-isosorbide terephthalate).

Sustainable development greatly benefits from the effective synthesis of bio-based copolymers that are environmentally friendly. To enhance the polymerization reactivity for the production of poly(ethylene-co-isosorbide terephthalate) (PEIT), five highly active Ti-M (M = Mg, Zn, Al, Fe, and Cu) bimetallic coordination catalysts were designed. The catalytic activity of Ti-M bimetallic coordination catalysts and single Sb- or Ti-based catalysts was compared, and the effects of catalysts with a different type of coordination metal (Mg, Zn, Al, Fe, and Cu) on the thermodynamic and crystallization properties of copolyesters were explored. In polymerization, it was found that Ti-M bimetallic catalysts with 5 ppm (Ti) had higher catalytic activity than traditional antimony-based catalysts or Ti-based catalysts with 200 ppm (Sb) or 5 ppm (Ti). The Ti-Al coordination catalyst showed the best-improved reaction rate of isosorbide among the five transition metals used. Utilizing Ti-M bimetallic catalysts, a high-quality PEIT was successfully synthesized with the highest number-average molecular weight of 2.82 × 104 g/mol and the narrowest molecular weight distribution index of 1.43. The glass-transition temperature of PEIT reached 88.3 °C, allowing the copolyesters to be used in applications requiring a higher Tg, like hot filling. The crystallization kinetics of copolyesters prepared by some Ti-M catalysts was faster than that of copolyesters prepared by conventional titanium catalysts.

MOF-derived bimetallic coordination polymer@cobalt-aluminum layered double hydroxide for highly selective CO2 adsorption: Experiments, mechanisms

Selective capture of CO2 is one of the most effective strategies for combating the greenhouse effect. In this study, we report the synthesis of a novel adsorbent—an amine-based cobalt-aluminum layered hydroxide with a hafnium/titanium metal coordination polymer (denoted as Co-Al-LDH@Hf/Ti-MCP-AS)—through the derivatization of metal–organic frameworks (MOFs) for selective CO2 adsorption and separation. Co-Al-LDH@Hf/Ti-MCP-AS achieved the maximum CO2 adsorption capacity of 2.57 mmol g−1 at 25 °C and 0.1 MPa. The adsorption behavior followed the pseudo-second-order kinetics and Freundlich isotherm models, indicating that chemisorption occurs on a non-homogeneous surface. Co-Al-LDH@Hf/Ti-MCP-AS also exhibited selective CO2 adsorption in CO2/N2 and excellent stability over six adsorption–desorption cycles. An in-depth analysis of the adsorption mechanism through X-ray photoelectron spectroscopy and density-functional theory and frontier molecular orbital calculations revealed that adsorption occurs through acid–base interactions between amine functional groups and CO2 and that the tertiary amines (N3) have the highest affinity toward CO2. Our study provides a novel strategy for designing high-performance adsorbents for CO2 adsorption and separation.

Rechargeable non-aqueous lithium-O2 batteries: Novel bimetallic (Ni-Cu) conductive coordination polymer cathodes

The development of highly efficient catalysts for the reactions of oxygen reduction (ORR) and oxygen evolution (OER) is crucial for lithium-O2 (Li-O2) batteries. Herein is synthesized a π-d conjugated bimetallic coordination polymer (NiCu-BTA) by the aid of the chemical deposition method and applied as cathode catalyst for Li-O2 batteries. Due to the difference in the electronic structures of Ni and Cu, the degree-disorder and porosity of NiCu-BTA increased compared with the pure Ni-BTA and Cu-BTA, resulting in an enhanced electrocatalytic activity and battery performance. At a current density of 100 mA g−1, the Li-air battery equipped with NiCu-BTA shows a discharge specific capacity of 23,000 mAh g−1 and can be consistently cycled up to 113 times. The tunable catalytic activity in M-BTA opens a new window for the design of low-cost and multifunctional catalysts, and may find potential applications in clean and renewable energy fields.

Adsorption of Water Vapour on the Microstructure and Stability of Cu-Zn Bimetallic Coordination Polymer

A current challenge in the design of synthesis lies in the incorporation of two or more transition metals into a coordination polymer. The most widely used approach has been to incorporate a second metal as a generally innocent (coordinatively saturated) part of a linear linker as in the case of multifunctional carboxylated porphyrins (MCPs). The empirical method has been used to obtain many other types of MCPs; however, the selective, direct replacement of one transition metal within a monometallic coordination polymer via controlled stoichiometry has not generally led to maintained structural fidelity. In this present work, three pyromellitic acid complexes were synthesized at room temperature and characterized by Elemental analysis, Powder X-ray diffraction, Fourier transform infrared spectroscopy, Scanning electron microscopy, N2 adsorption-desorption Isotherm, and Thermal analysis. The reaction in water-methanol between pyromellitic acid and copper ions by ambient precipitation method formed [CuH2B4C]·5H2O. When zinc is combined with copper and the ligand, [Cu2Zn(B4C)1.5(H2O)4.5]·9H2O is formed. A repeat of this step under solvothermal condition produced Solvo-[Cu2Zn(B4C)1.5(H2O)5]·2H2O. The N2-adsorption isotherm of these compounds showed them to be Type III according to the IUPAC classification, with small pores only capable of small molecule sorption.
 Keywords: Coordination, microporous, polymer, pyromellitic, sorption

Highly efficient and easy separation of polysaccharide-based cyanide-bridged bimetallic coordination polymers for thallium removal: Performance and mechanisms

It is significant to develop functional materials with high selectivity, high adsorption capacity and easy separation to reduce thallium (Tl) pollution caused by human activities. Polysaccharide-based cyanide-bridged bimetallic coordination polymers (PCBPs) were developed for the removal of Tl(I) and Tl(Ⅲ) simultaneously, and the effects of lists of conditions on the removal of Tl showed that the maximum adsorption rate of Tl reached 98.3 % after 180 min. Meanwhile, the stable adsorption efficiency of Tl could be maintained in a wide range of pH. Moreover, even in the interfering system where high-intensity cations and total organic matter coexist, PCBPs still showed excellent Tl removal efficiency. Notably, the amphoteric structure of PCBPs provided many chemical chelation sites, significantly improving the adsorption capacity of PCBPs for Tl. Importantly, XRD, SEM, TEM, BET, and magnetization tests show that PCBP has a large pore and specific surface area, stable structure, and recyclable magnetic characteristics conducive to the adsorption of thallium. More importantly, the π-π conjugation and chelation of the above functional groups with Tl(I) and Tl(Ⅲ) were well confirmed by FT-IR and XPS for their adsorption mechanism. What is more, the adsorption isotherm and kinetics agreed with the Freundlich model and the pseudo-second-order model, respectively, indicating that the adsorption of Tl was a multi-layer chemical adsorption process. Besides, the Gibbs free energy was negative, indicating that the adsorption process of Tl was spontaneous. Therefore, the polysaccharide-loaded ferric ferrocyanide coordination polymer exhibited high-efficiency and selectivity removal of Tl(I) and Tl(Ⅲ), which would provide technical support and theoretical guidance for the treatment of thallium-containing wastewater.