Boron Imidazolate Framework Research Articles

B Doped Zn Single‐Atom Nanozyme With Enhanced Oxidase‐Like Activity Combined CRISPR/Cas13a System for RNA Sensing

AbstractSingle‐atom nanozyme (SAZ) with peroxidase‐like activity has attracted great attention in point‐of‐care (POC) diagnostic, but the use of unstable H2O2 in peroxidase catalytic reactions often leads to low detection accuracy. Thus, developing SAZ with high oxidase (OD)‐like activity to construct RNA sensing systems independent of H2O2 is imperative for improving accuracy. Herein, a novel strategy to fabricate boron‐nitrogen co‐doped zinc SAZ (ZnBNC‐SAZ) with excellent OD‐like activity by carbonizing Zn based zeolitic boron imidazolate frameworks is reported. The electron deficient B in imidazolate ligand can form Zn─N─B bond in situ during high temperature pyrolysis, which can regulate the electronic structure of Zn and further upshift the d‐band center of Zn to improve the OD‐like activity. With ZnBNC‐SAZ as signal generator, a new method for sensitive RNA detection is developed by combining CRISPR/ cas13 system with terminal deoxynucleotidyl transferase‐induced DNA extension reaction. The limits of detection for RNAs are as low as 20 aM. The proposed biosensor is adaptable to a lateral‐flow‐based readout and is universally applicable for sensing various RNAs by programming the guide RNA. Importantly, the proposed biosensor can monitor the cellular differentiation and identify patients with cervical carcinoma, showing great potential for application in facile POC diagnosis.

Fine-Tuning the d-Band Center Position of Zinc to Increase the Anti-Tumor Activity of Single-Atom Nanozymes.

The exceptional biocompatibility of Zn-based single-atom nanozymes (SAzymes) has led to extensive research in their application for disease diagnosis and treatment. However, the fully occupied 3d10 electron configuration has seriously hampered the enzymatic-like activity of Zn-based SAzymes. Herein, a B-doped Zn-based SAzymes is fabricated by carbonizing zeolite-like Zn-based boron imidazolate framework at different temperatures (Zn-SAs@BNCx, x = 800, 900, 1000, and 1100°C). The formed B─N bond yielded a local electric field, which changes the position of the d-band center and improved the oxidation state of Zn by facilitating the electron transfer from Zn to N to B. These changes enhanced the adsorption and activation of H2O2 and O2 by Zn-SAs@BNC1000, increasing the nanozymes' multi-enzyme catalytic activity. B doping led to 24.81-, 32.37-, and 13.98-fold increase in the peroxidase-, oxidase- and catalase-like, respectively, catalytic efficiency (Kcat/Km) of Zn-SAs@BNC1000 when compared with no B doping. In addition, Zn-SAs@BNC1000 showed excellent ability to kill tumor cells both in vitro and in vivo. This study demonstrates that the modulation of the electron configuration of Zn is an effective strategy to develop efficient anti-tumor approaches by boosting the enzymatic activity of Zn-based SAzymes.

Enhancing CO2 electroreduction to ethylene via microenvironment regulation in boron-imidazolate frameworks.

Using the structure-induced effect of KBH(mim)3 ligand, four 2-dimensional (2D) boron imidazolate frameworks with identical body framework and different dangling monocarboxylate ligands, have been synthesized. Electrocatalytic results indicate that the surrounding microenvironment regulation could effectively affect the activity and selectivity towards C2H4. BIF-151 showed the highest electrocatalytic performances with the Faraday efficiency (FE) of 25.94% for C2H4 at -1.4 V vs. RHE.

Dual-Step Redox Engineering of 2D CoNi-Alloy Embedded B, N-Doped Carbon Layers Toward Tunable Electromagnetic Wave Absorption and Light-Weight Infrared Stealth Heat Insulation Devices.

2D layered metallic graphite composites are promising electromagnetic wave absorption materials (EWAMs) for their combined properties of abundant interlayer free spaces, rich metallic polarized sites, and high conductivity, but the controllable synthesis remains rather challenging. Herein, a dual-step redox engineering strategy is developed by employing cobalt boron imidazolate framework (Co-BIF) to construct 2D CoNi-alloy embedded B, N-doped carbon layers (2D-CNC) as a promising EWAM. In the first step, a chemical etching oxidation process on Co-BIF is used to obtain an optimized 2D-CoNi-layered double hydroxide (2D-CoNi-LDH) intermediate and in the second, high-temperature calcination reduction is implemented to modify graphitization of the degree of the 2D-CNC. The obtained sample delivers superior reflection loss (RLmin) of -60.1dB and wide effective absorption bandwidth (EAB) of 6.24GHz. The synergy mechanisms of interfacial/dipole polarization and magnetic coupling are in-depth evidenced by the hologram and Lorentz electron microscopy, revealing its significant contribution on multireflection and impedance matching. Further theoretical evaluation by COMSOL simulation in different fields based on the dynamic loss process toward the test ring reveals the in situ EW attenuation process. This work presents a strategy to develop multifunctional light-weight infrared stealthy aerogel with superior pressure-resistant, anti-corrosion, and heat-insulating properties for future applications.

Boron-imidazolate coordination networks with 3d transition metals for enhanced CO2 adsorption capability

The synthesis conditions of sodalite (SOD)-topology coordination networks with boron-imidazolate frameworks containing various 3d transition metals were systematically investigated to control the crystal growth process and enhance their CO2 adsorption capability.

Enhancing Electroreduction CO2 to Hydrocarbons via Tandem Electrocatalysis by Incorporation Cu NPs in Boron Imidazolate Frameworks.

Due to the higher value of deeply-reduced products, electrocatalytic CO2 reduction reaction (CO2 RR) to multi-electron-transfer products has received more attention. One attractive strategy is to decouple individual steps within the complicated pathway via multi-component catalysts design in the concept of tandem catalysts. Here, a composite of Cu@BIF-144(Zn) (BIF = boron imidazolate framework) is synthesized by using an anion framework BIF-144(Zn) as host to impregnate Cu2+ ions that are further reduced to Cu nanoparticles (NPs) via in situ electrochemical transformation. Due to the microenvironment modulation by functional BH(im)3 - on the pore surfaces, the Cu@BIF-144(Zn) catalyst exhibits a perfect synergetic effect between the BIF-144(Zn) host and the Cu NP guest during CO2 RR. Electrochemistry results show that Cu@BIF-144(Zn) catalysts can effectively enhance the selectivity and activity for the CO2 reduction to multi-electron-transfer products, with the maximum FECH4 value of 41.8% at -1.6V and FEC2H4 value of 12.9% at -1.5V versus RHE. The Cu@BIF-144(Zn) tandem catalyst with CO-rich microenvironment generated by the Zn catalytic center in the BIF-144(Zn) skeleton enhanced deep reduction on the incorporated Cu NPs for the CO2 RR to multi-electron-transfer products.

Experimental Investigation of Thermodynamic Stabilization in Boron Imidazolate Frameworks (BIFs) Synthesized by Mechanochemistry.

This study experimentally explores the energetics for the formation of boron-imidazolate frameworks (BIFs), which are synthesized by mechanochemistry. The topologically similar frameworks employ the same tetratopic linker based on tetrakis(imidazolyl)boric acid but differ in the monovalent cation metal nodes. This permits assessment of the stabilizing effect of metal nodes in frameworks with sodalite (SOD) and diamondoid (dia) topologies. The enthalpy of formation from endmembers (metal oxide and linker), which define thermodynamic stability of the structures, has been determined by use of acid solution calorimetry. The results show that heavier metal atoms in the node promote greater energetic stabilization of denser structures. Overall, in BIFs the relation between cation descriptors (ionic radius and electronegativity) and thermodynamic stability depends on framework topology. Thermodynamic stability increases with the metallic character of the cation employed as the metal node, independent of the framework topology. The results suggest unifying aspects for thermodynamic stabilization across MOF systems.

Homochiral boron imidazolate frameworks built from mixed Chiral and achiral ligands

Chiral metal-organic frameworks (MOFs) have been studied extensively because of the potential application. Based on the complexity of chiral structure, it is a great challenge to study the formation of novel chiral centers under self-assembly conditions. By mixing chiral and achiral ligands, five unusual homochiral BIFs materials were synthesized by using d-camphoric acid (D-H2cam) and KBH(mim)3 (mim = 2-methylimidazole) under solvothermal condition. The orientations of mim rings had been locked to a specific angle in these structures and freed tridentate BH(mim)3- ligands were separated into two enantiomers, S–BH(mim)3- and R–BH(mim)3-. BIF-123 and BIF-124 exhibited similar (3, 4)-connected pillared-layer chiral structures with a pair of opposite helical substructures. BIF-125, 126 and 127 exhibited a 4-connected chiral diamond structure, which incorporates the homochiral helical substructures containing only S–BH(mim)3- ligand. These homochiral BIFs showed high pore volume in gas adsorption measurements and good stability under different solvent environments. Furthermore, the obvious CD signals of BIF-126 proved the chirality of bulk samples.

Advanced BIFs with Co, B, N, and S for Electrocatalytic Oxygen Reduction and Oxygen Evolution Reactions.

In this work, a new alkaline-stable boron imidazolate framework (BIF-90) was rationally designed and successfully synthesized by solvothermal reaction. Due to its potential electrocatalytic active sites (Co, B, N, and S) and chemical stabilities, BIF-90 was explored as a bifunctional electrocatalyst toward electrochemical oxygen reactions, namely, oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). This work will open new avenues toward the design of stable, cheap, and more active BIFs as bifunctional catalysts.

Raman scattering spectra of boron imidazolate frameworks containing different magnetic ions.

We present a Raman scattering spectroscopic study of boron imidazolate metal-organic frameworks (BIFs) with three different magnetic metal ions and one non-magnetic in a wide frequency range from 25 to 1700 cm-1, which covers local vibrations of the imidazolate linkers as well as collective lattice vibrations. We show that the spectral region above 800 cm-1 belongs to the local vibrations of the linkers, which have the same frequencies for the studied BIFs without any dependence on the structure of the BIFs and are easily interpreted based on the spectra of imidazolate linkers. In contrast, collective lattice vibrations, observed below 100 cm-1, show a distinction between cage and two-dimensional BIFs structures, with a weak dependence on the metal node. We identify the range of vibrations around 200 cm-1, which are distinct for each metal-organic framework, depending on a metal node. Our work demonstrates the energy hierarchy in the vibrational response of BIFs.

Enhancing CO2 Electroreduction to Ethylene via Copper−Silver Tandem Catalyst in Boron‐Imidazolate Framework Nanosheet

AbstractCopper‐based tandem catalysts with a well‐defined Cu coordination environment for the electrochemical CO2 reduction reaction (CO2RR) are highly desirable, due to their unique geometric‐electronic properties and helpfulness for revealing structure–property correlations. Here, this work synthesizes a tandem catalyst at atomic configuration scale, Ag@BIF‐104NSs(Cu), by using the ultrathin boron imidazolate framework (BIF) nanosheets as support to load Ag nanoparticles (NPs). Due to the highly ordered benzoate ligands decorated on the Cu sites of BIF‐104NSs(Cu), Ag NPs are located in atomic proximity to Cu sites via a coordination effect. Electrochemical CO2RR measurements show this tandem catalyst highly improves the selectivity and activity for the CO2 reduction to ethylene. The faradaic efficiency (FEC2H4) of 21.43% is significantly higher than that of BIF‐104NSs(Cu) (3.82%). Further, density functional theory calculations reveal that the Ag sites in the composite can efficiently reduce CO2 to *CO, that subsequently migrate to the Cu sites. Thereafter, the Cu–Ag atom pair is responsible for the C–C coupling of the local enriched *CO and further formation of C2H4.

Highly efficient metal-free borocarbonitride catalysts for electrochemical reduction of N2 to NH3

The electrocatalytic nitrogen reduction reaction (NRR) for ammonia (NH3) under ambient conditions is emerging as a potentially sustainable alternative to the traditional, energy-intensive Haber-Bosch process for ammonia production. Currently, metal-based electrocatalysts constitute the majority of reported NRR catalysts. However, they often suffer from the shortcomings of competitive reactions of nitrogen adsorption/activation and hydrogen generation. Therefore, there is an urgent need to develop more environmentally friendly, low energy consumption, and non-polluting high-performance metal-free electrocatalysts. In this study, borocarbonitride (BCN) materials derived from boron imidazolate framework (BIF-20) were used to boost efficient electrochemical nitrogen conversion to ammonia under ambient conditions. The BCN catalyst demonstrated excellent performance in 0.1 M KOH, with an ammonia yield of 21.62 μg h−1 mgcat-1 and a Faradaic efficiency of 9.88% at −0.3 V (Reversible Hydrogen Electrode, RHE). This performance is superior to most metal-free catalysts and even some metal catalysts for NRR. The 15N2/14N2 isotope labeling experiments and density functional theory (DFT) calculations showed that N2 can be adsorbed and converted to NH3 on the surface of BCN, and that the energy barrier can be significantly reduced by structural design for BCN. This work highlights the important role played by the presence of Lewis acid-base pairs in metal-free catalysts for enhancing electrochemical NRR performance.

Hydroxyl reduced silver nanoparticles on ultrathin boron imidazolate framework nanosheets for electrocatalytic CO2 reduction

A composite of Ag@BIF-73NSs obtained by loading Ag NPs on BIF nanosheets (BIF-73NSs) via the hydroxyl functional group can be used as an electrocatalyst for electroreduction of CO2 to CO with a FE close to 90%.

Fine-Tuning Tridentate Ligands for the Construction of Nanotube-Based Boron Imidazolate Frameworks with High Chemical Stability

Two unusual nanotube-based boron imidazolate frameworks (BIF-134 and BIF-135) were synthesized by a dual-ligand synthetic strategy under solvothermal conditions. In the structure of BIF-134 ([Co(BH(2-mim)3)(BTC)1/3](HBH(2-mim)3)1/3(NMA); 2-mim = 2-methylimidazole, NMA = N-methylacetamide, and BTC = 1,3,5-benzene tricarboxylate), one part of boron imidazolate ligands participate in the structural skeleton coordination, while another part of boron imidazolate ligands act as guest molecules that are located between adjacent nanotubes, which enhance the stability of the framework by the host-guest interaction and the pore space partition effects. It was found to be highly stable in air, water, organic solvents, and a wide pH range (pH 0-12). However, in the structure of BIF-135 ([Zn(BH(2-mim)3)(CHTC)1/3]; CHTC = 1,3,5-cyclohexanetricarboxylate), all boron imidazolate ligands participate in the structural skeleton coordination; there is no boron imidazolate guest molecule in the pores. The topology of BIF-135 is similar to that of BIF-134 by replacing BTC with CHTC and replacing Co with Zn. Furthermore, the obtained BIFs exhibited third-order nonlinear optical properties and potential optical limiting applications demonstrated by reverse saturable absorption.

Copper boron–imidazolate framework incorporated chitosan membranes for bacterial-infected wound healing dressing

Chronic wounds resulting from bacterial infection are a global healthcare challenge as they usually impair the healing process and induce various complications. In this work, a chitosan (CS) membrane loaded with copper boron–imidazolate framework (Cu–BIF) was successfully prepared by self-assembly method for bacterial-infected wound-healing dressing. The as-prepared Cu–BIF/CS membrane possessed desirable biocompatibility. The antibacterial activity of Cu–BIF/CS membrane was evaluated by the spread plate and disc diffusion method, which was also verified by the fluorescence-based viability and morphological changes of bacteria. Moreover, Cu–BIF/CS membrane could increase wound closure rate and accelerate skin regeneration via combination therapy with chitosan, Cu2+ and hydroxyl radicals during infected wound healing process. These results exhibit that Cu–BIF/CS membrane has great potential as wound dressings in the field of clinical treatment of bacterial-infected wounds.

Induction of Chirality in Boron Imidazolate Frameworks: The Structure-Directing Effects of Substituents.

By enhancing steric hindrance of substituents on the imidazole ring, the fan-shaped molecule of a tridentate boron imidazolate ligand (KBH(2-ipim)3, 2-ipim = 2-isopropylimidazolate) with racemic chirality was obtained. Then, seven novel boron imidazolate frameworks (BIFs) were prepared by mixing KBH(2-ipim)3 ligands with various derivatives of benzene carboxylic acid under solvothermal conditions. All of these seven materials contain a ladder-like zinc-boron-imidazolate chain as a basic building block, and the ligand BH(2-ipim)3- exists in the same handedness in one chain. The structural variations are associated with the position of substituents of the auxiliary ligand. Of particular interest is the spontaneous resolution of BH(2-ipim)3- ligands into two independent enantiomorphous homochiral structures, BIF-131-S and BIF-131-R, which contain both a chiral chain and an absolute helix embedded in the nets.

Synthesis of chiral boron imidazolate frameworks with second-order nonlinear optics

The synthesis of crystalline homochiral MOF materials is very important for their potential application in enantioselective processes and asymmetric catalysis. In this paper, four novel zinc based chiral boron imidazolate frameworks (BIFs), Zn2[BH(2-eim)3](BA)2(OH) (BIF-132-BA, 2-eim ​= ​2-ethylimidazolate, BA ​= ​benzoate), Zn[HBH(2-ipim)3](OHBA)(Ac) (BIF-133-OHBA, 2-ipim ​= ​2-isopropylimidazolate, OHBA ​= ​o-hydroxybenzoate, Ac ​= ​acetate), Zn[HBH(2-ipim)3](PHBA)(Ac) (BIF-133-PHBA, PHBA ​= ​p-hydroxybenzoate), and Zn[HBH(2-ipim)3](DHBA)(Ac) (BIF-133-DHBA, DHBA ​= ​2,4-dihydroxybenzoate) were prepared via solvothermal synthesis. Single-crystal X-ray diffraction demonstrated that the existence of hydrogen bonds between adjacent chains results in two different structure features of BIF-131: a chiral ladder-like 1D chain (BIF-133-OHBA) and two supramolecular 2D layers (BIF-133-PHBA and BIF-133-DHBA). Then, the optical activities of as-synthesied crystals were preliminarily studied by circular dichroism (CD) spectroscopy. In addition, because they crystallized in noncentrosymmetric space groups, the powder second-harmonic generation (SHG) measurements were carried out and the SHG response of BIF-133-PHBA was almost comparable to potassium dihydrogen phosphate (KDP).

Infection microenvironment-activated core-shell nanoassemblies for photothermal/chemodynamic synergistic wound therapy and multimodal imaging

The development of intelligent designs of new antibacterial modalities for diagnosing and treating chronic multidrug-resistant bacterial infections is an urgent need, but achieving the precisive theranostic in response to specific inflammatory microenvironments remains a great challenge. This paper describes our work designing and demonstrating infection microenvironment-activated core-shell Gd-doped Bi2S3@Cu(II) boron imidazolate framework (Bi2S3:Gd@Cu-BIF) nanoassemblies. Upon exposure to a single beam of 808 nm laser, Bi2S3:Gd@Cu-BIF nanoassemblies showed exceptional photothermal conversion (η = 52.6%) and produced several cytotoxic reactive oxygen species, such as singlet oxygen and hydroxyl radicals, by depleting the intracellular glutathione and in-situ catalyzing the decomposition of endogenous hydrogen peroxide in the inflammatory microenvironment. The broad-spectrum antibacterial properties of nanoassemblies were confirmed to be effective against Escherichia coli (E. coli) and methicillin-resistant Staphylococcus aureus (MRSA) with an inhibition rate of 99.99% in vitro. Additionally, in vivo wound-healing studies revealed that Bi2S3:Gd@Cu-BIF nanoassemblies could serve as an effective wound spray to accelerate healing following MRSA infections via photothermal/chemodynamic (PTT/CDT) synergistic therapy. The effective wound healing rate in the synergistic treatment group was 99.8%, which is higher than the 69.5% wound healing rate in the control group. Furthermore, magnetic resonance and computed tomography dual-modal imaging mediated by Bi2S3:Gd@Cu-BIF nanoassemblies also exhibits promising potential as an integrated diagnostic nanoplatform. Overall, this work provides useful insights for developing all-in-one theranostic nanoplatforms for clinical treatment of drug-resistant bacterial infections. Statement of significanceNew treatments and effective diagnostic strategies are critical for fighting drug-resistant bacterial infections. Infection microenvironment-activated Bi2S3@Cu-BIF nanoassemblies can simultaneously increase eigen temperature and generate cytotoxic reactive oxygen species, such as singlet oxygen and hydroxyl radicals, under near-infrared laser irradiation, achieving the synergistic effect of photothermal and chemodynamic therapy, which has been proven to be highly effective for inhibiting bacterial activity and speeding wound healing from methicillin-resistant Staphylococcus aureus infection. More importantly, the nanoassemblies could enable early precise visualized detection of bacterial abscess using magnetic resonance/computed tomography dual-modal bio-imaging techniques.

Efficient neutron radiation shielding by boron-lithium imidazolate frameworks.

Radiation protective materials are widely applied to avoid occupational hazards from either particle emissions or high-energy electromagnetic waves. Herein, we present a boron imidazolate framework (BIF) as a novel neutron shielding additive with high neutron capture cross-section elements B/Li and H. The BIF1-based epoxy resin matrix (Ep-BIF1) possesses high thermal stability and excellent resistance capacity. The neutron radiation shielding property was characterized using an Am-Be source, in which the thermal neutron shielding efficiency of Ep-BIF1 is notably higher than that of Ep-B4C with equal boron concentration, showing potential applications as an advanced efficient neutron radiation shielding composite.

Composite of CsPbBr3 with Boron Imidazolate Frameworks as an Efficient Visible-Light Photocatalyst for CO2 Reduction

Composite of CsPbBr₃ with Boron Imidazolate Frameworks as an Efficient Visible-Light Photocatalyst for CO₂ Reduction