Molecular Simulation Studies of Pharmaceutical Pollutant Removal (Rosuvastatin and Simvastatin) Using Novel Modified-MOF Nanostructures (UIO-66, UIO-66/Chitosan, and UIO-66/Oxidized Chitosan)

The ubiquitous presence of pharmaceutical pollutants in the environment significantly threatens human health and aquatic ecosystems. Conventional wastewater treatment processes often fall short of effectively removing these emerging contaminants. Therefore, the development of high-performance adsorbents is crucial for environmental remediation. This research utilizes molecular simulation to explore the potential of novel modified metal-organic frameworks (MOFs) in pharmaceutical pollutant removal, paving the way for the design of efficient wastewater treatment strategies. Utilizing UIO-66, a robust MOF, as the base material, we developed UIO-66 functionalized with chitosan (CHI) and oxidized chitosan (OCHI). These modified MOFs' physical and chemical properties were first investigated through various characterization techniques. Subsequently, molecular dynamics simulation (MDS) and Monte Carlo simulation (MCS) were employed to elucidate the adsorption mechanisms of rosuvastatin (ROSU) and simvastatin (SIMV), two prevalent pharmaceutical pollutants, onto these nanostructures. MCS calculations demonstrated a significant enhancement in the adsorption energy by incorporating CHI and OCHI into UIO-66. This increased ROSU from -14,522 to -16,459 kcal/mol and SIMV from -17,652 to -21,207 kcal/mol. Moreover, MDS reveals ROSU rejection rates in neat UIO-66 to be at 40%, rising to 60 and 70% with CHI and OCHI. Accumulation rates increase from 4 Å in UIO-66 to 6 and 9 Å in UIO-CHI and UIO-OCHI. Concentration analysis shows SIMV rejection surges from 50 to 90%, with accumulation rates increasing from 6 to 11 Å with CHI and OCHI in UIO-66. Functionalizing UIO-66 with CHI and OCHI significantly enhanced the adsorption capacity and selectivity for ROSU and SIMV. Abundant hydroxyl and amino groups facilitated strong interactions, improving performance over that of unmodified UIO-66. Surface functionalization plays a vital role in customizing the MOFs for pharmaceutical pollutant removal. These insights guide next-gen adsorbent development, offering high efficiency and selectivity for wastewater treatment.

Ionic Liquid Modified Fe-Porphyrinic Metal-Organic Frameworks as Efficient and Selective Photocatalysts for CO2 Reduction

Porphyrin-based metal-organic frameworks (MOFs) are ideal platforms for heterogeneous photocatalysts toward CO2 reduction. To further explore photocatalytic MOF systems, it is also necessary to consider their ability to fine-tune the microenvironments of the active sites, which affects their overall catalytic operation. Herein, a kind of ionic liquid (IL, here is 3-butyric acid-1-methyl imidazolium bromide, BAMeImBr) was anchored to iron-porphyrinic Zr-MOFs with different amounts to obtain ILx@MOF-526 (MOF-526 = Zr6O4(OH)4(FeTCBPP)3, FeTCBPP = iron 5,10,15,20-tetra[4-(4'-carboxyphenyl)phenyl]-porphyrin, x = 100, 200, and 400). ILx@MOF-526 series was designed to investigate the effects of the microenvironmental and electronic structural modification on the efficiency and selectivity of the photochemical reduction of CO2 after introducing IL fragments. Compared to parent MOF-526, the production and selectivity of CO were greatly improved in the absence of any photosensitizer under visible light by the ILx@MOF-526 series. Among them, the CO yield of IL200@MOF-526 was up to 14.0 mmol g-1 within 72 h with a remarkable CO selectivity of 97%, which is superior to that of MOF-526 without BAMeIm+ modification and other amounts of BAMeIm+ loaded. Furthermore, density functional theory calculations were performed to study the mechanism of the CO2 reduction.

Nickel-Iron-Modified 2D Metal-Organic Framework as a Tunable Precatalyst for Electrochemical Water Oxidation

Mixed-metal metal-organic framework (MOF)-based water oxidation precatalysts have aroused a great deal of attention due to their remarkable catalytic performance. Yet, despite significant advancement in this field, there is still a need to design new MOF platforms that allow simple and systematic control over the final catalyst's metal composition. Here, we show that a Zr-BTB 2D-MOF could be used to construct a series of Ni-Fe-based oxide hydroxide water oxidation precatalysts with diverse Ni-Fe compositions. In situ Raman spectroscopy characterization revealed that the MOF precatalysts could be electrochemically converted to the active catalysts (NiFeOOH). In turn, it was found that the highest water oxidation activity was obtained with a catalyst containing a 47:53 Ni:Fe molar ratio. Additionally, the obtained catalyst is also active toward electrochemical methanol oxidation, exhibiting high selectivity toward the formation of formic acid. Hence, these results could pave the way for the development of efficient electrocatalytic materials for a variety of oxidative reactions.

Miniature Optical Fiber Fabry-Perot Interferometer Based on a Single-Crystal Metal-Organic Framework for the Detection and Quantification of Benzene and Ethanol at Low Concentrations in Nitrogen Gas

This study reports for the first time, to the best of our knowledge, a real-time detection of ultralow-concentration chemical gases using fiber-optic technology, combining a miniaturized Fabry-Perot interferometer (FPI) with metal-organic frameworks (MOFs). The sensor consists of a short and thick-walled silica capillary segment spliced to a lead-in single-mode fiber (SMF), housing a tiny single crystal of HKUST-1 MOF, imparting chemoselectivity features. Ethanol and benzene gases were tested, resulting in a shift in the FPI interference signal. The sensor demonstrated high sensitivity, detecting ethanol gas concentrations (EGCs) with a sensitivity of 0.428 nm/ppm between 24.9 and 40.11 ppm and benzene gas concentrations (BGCs) with a sensitivity of 0.15 nm/ppm between 99 and 124 ppm. The selectivity study involved a combination of three ultralow concentrations of ethanol, benzene, and toluene gases, revealing an enhancement factor of 436% for benzene and 140% for toluene, attributed to the improved miscibility of these conjugated ring molecules with the alkane chains of the ethanol-modified HKUST-1. Experimental tests confirmed the sensor's viability, demonstrating significantly improved response time and spectral characteristics through crystal polishing, indicating its potential for quantifying and detecting chemical gases at ultralow concentrations. This technology may prevent energy resource losses, and the sensor's small size and robust construction make it applicable in confined and hazardous locations.

Transformational Modulation of Fluorescence to Room Temperature Phosphorescence in Metal-Organic Frameworks with Flexible C-S-C Bonds

Photoluminescent metal-organic frameworks (MOFs) have been a subject of considerable interest for many years. However, the regulation of excited states of MOFs at the single crystal level remains restricted due to a lack of control methods. The singlet-triplet emissive property can be significantly influenced by crystal conformational distortions. This review introduces an intelligent responsive MOF material, denoted as LIFM-SHL-3a, characterized by flexible C-S-C bonds. LIFM-SHL-3a integrates elastic structural dynamics with fluorescence and room temperature phosphorescence (RTP) modulation under heating conditions. The deformable carbon-sulfur bond essentially propels the distortion of molecular conformation and alters the stacking mode, as illustrated by single-crystal-to-single-crystal transformation detection. The deformation of flexible C-S-C bonds leads to different noncovalent interactions in the crystal system, thereby achieving modulation of the fluorescence (F) and RTP bands. In the final state structure, the ratio of fluorescence is 66.7%, and the ratio of RTP is 32.6%. This stands as a successful demonstration of modulating F/RTP within the dynamic MOF, unlocking potential applications in optical sensing and beyond. Especially, a PL thermometer with a relative sensitivity of 0.096-0.104%·K-1 in the range of 300-380 K and a H2S probe with a remarkably low LOD of 125.80 nM can be obtained using this responsive MOF material of LIFM-SHL-3a.

Zr-Based MOF-545 Metal-Organic Framework Loaded with Highly Dispersed Small Size Ni Nanoparticles for CO2 Methanation

We report the use of Zr-based metal-organic frameworks (MOFs) MOF-545 and MOF-545(Cu) as supports to prepare catalysts with uniformly and highly dispersed Ni nanoparticles (NPs) for CO2 hydrogenation into CH4. In the first step, we studied the MOF support under catalytic conditions using operando diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, ex situ characterizations (PXRD, XPS, TEM, and EDX-element mapping), and DFT calculations. We showed that the high-temperature conditions undoubtedly confer a potential for catalytic functionality to the solids toward CH4 production, while no role of the Cu could be evidenced. The MOF was shown to be transformed into a catalytically active material, amorphized but still structured with dehydroxylated Zr-oxoclusters, in line with DFT calculations. In the second step, Ni@MOF-545 catalysts were prepared using either impregnation (IM) or double solvent (DS) methods, followed by a dry reduction (R) route under H2 to immobilize Ni NPs. The highest catalytic activity was obtained with the Ni@MOF-545 DS R catalyst (595 mmolCH4 gNi-1 h-1) with 100% CH4 selectivity and 60% CO2 conversion after ∼3 h. The higher catalytic activity of Ni@MOF-545 DS R is a result of much smaller (∼5 nm) and better dispersed Ni NPs than in the IM sample (20-40 nm), the latter exhibiting sintering. The advantages of the encapsulation of Ni NPs by the DS method and of the use of a MOF-545-based support are discussed, highlighting the interest of designing yet-unexplored Zr-based MOFs loaded with Ni NPs for CO2 hydrogenation.

MatGD: Materials Graph Digitizer

We developed Material Graph Digitizer (MatGD), which is a tool for digitizing a data line from scientific graphs. The algorithm behind the tool consists of four steps: (1) identifying graphs within subfigures, (2) separating axes and data sections, (3) discerning the data lines by eliminating irrelevant graph objects and matching with the legend, and (4) data extraction and saving. From the 62,534 papers in the areas of batteries, catalysis, and metal-organic frameworks (MOFs), 501,045 figures were mined. Remarkably, our tool showcased performance with over 99% accuracy in legend marker and text detection. Moreover, its capability for data line separation stood at 66%, which is much higher compared to those of other existing figure-mining tools. We believe that this tool will be integral to collecting both past and future data from publications, and these data can be used to train various machine learning models that can enhance material predictions and new materials discovery.

Large Microsphere Structure of a Co/C Composite Derived from Co-MOF with Excellent Wideband Electromagnetic Microwave Absorption Performance

In the field of electromagnetic wave (EMW) absorption, carbon matrix materials based on metal-organic frameworks (MOFs) have drawn more interest as a result of their outstanding advantages, such as porous structure, lightweight, controlled morphology, etc. However, how to broaden the effective absorption bandwidth [EAB; reflection loss (RL) ≤ -10 dB] is still a challenge. In this paper, large microsphere structures of a Co/C composite composed of small particle clusters were successfully prepared by the solvothermal method and annealing treatment. At a filling ratio of 40 wt %, the Co/C composite shows attractive microwave absorption (MA) performance after being annealed at 600 °C in an atmosphere of argon. With an EAB of 6.32 GHz (9.92-16.24 GHz) and a thickness of just 2.57 mm, the minimum RL can be attained at -54.55 dB. Most importantly, the EAB can attain 7.12 GHz (10.88-18.0 GHz) when the thickness is 2.38 mm, which is larger than that of the majority of MOF-derived composites. The superior MA performance is strongly related to excellent impedance matching and a higher attenuation constant. This study provides a simple strategy for synthesizing a MOF-derived Co/C composite with a wide EAB.

Guest-Stimulated Nonplanar Porphyrins in Flexible Metal-Organic Frameworks

Nonplanar porphyrins with out-of-plane distortions play crucial roles in many biological functions and chemical applications. The artificial construction of nonplanar porphyrins usually involves organic synthesis and modification, which is a highly comprehensive approach. However, incorporating porphyrins into guest-stimulated flexible systems allows to manipulate the porphyrin distortion through simple ad/desorption of guest molecules. Here, a series of porphyrinic zirconium metal-organic frameworks (MOFs) is reported that exhibit guest-stimulated breathing behavior. X-Ray diffraction analysis and skeleton deviation plots confirm that the material suffers from porphyrin distortion to form a ruffled geometry under the desorption of guest molecules. Further investigation reveals that not only the degree of nonplanarity can be precisely manipulated but also the partial distortion of porphyrin in a single crystal grain can be readily achieved. As Lewis acidic catalyst, the MOF with nonplanar Co-porphyrin exhibits active properties in catalyzing CO2 /propylene oxide coupling reactions. This porphyrin distortion system provides a powerful tool for manipulating nonplanar porphyrins in MOFs with individual distortion profiles for various advanced applications.

Role of Transition Metals in Metal-Organic Frameworks as Nanoporous Ion Emitters for Thermal Ionization Mass Spectrometry

Thermal ionization mass spectrometry is a powerful analytical technique that allows for precise determination of isotopic ratios. Analysis of low abundance samples, however, can be limited by the ionization efficiency. Following an investigation into a new type of metal-organic hybrid material, nanoporous ion emitters (nano-PIEs), devised to promote the emission of analyte ions and reduce traditional sample loading challenges, this work evaluates the impact that changing the metal in the material has on the ionization of uranium (U). Being derived from metal-organic frameworks (MOFs), nano-PIEs inherit the tunability of their parent MOFs. The MOF-74 series has been well studied for probing the impact various framework metals (i.e., Mg, Mn, Co, Ni, Cu, Zn, and Cd) have on material properties, and thus, a series of nano-PIEs with different metals were derived from this isoreticular MOF series. Trends in ionization efficiency were studied as a function of ionization potential, volatility, and work function of the framework metals to gain a better understanding of the mechanism of analyte ionization. This study finds a correlation between the analyte ionization efficiency and nano-PIE framework metal volatility that is attributed to its tunable thermal stability and degradation behavior.

Utilization of Physical Anisotropy in Metal-Organic Frameworks via Postsynthetic Alignment Control with Liquid Crystal

Metal-organic frameworks (MOFs) represent crystalline materials constructed from combinations of metal and organic units to often yield anisotropic porous structures and physical properties. Postsynthetic methods to align the MOF crystals in bulk remain scarce yet tremendously important to fully utilize their structure-driven intrinsic properties. Herein, we present an unprecedented composite of liquid crystals (LCs) and MOFs and demonstrate the use of nematic LCs to dynamically control the orientation of MOF crystals with exceptional order parameters (as high as 0.965). Unique patterns formed through a facile multidirectional alignment of MOF crystals exhibit polarized fluorescence with the fluorescence intensity of a pattern dependent on the angle of a polarizer, offering potential use in various optical applications such as an optical security label. Further, the alignment mechanism indicates that the method is applicable to numerous combinations of MOFs and LCs, which include UV polymerizable LC monomers used to fabricate free-standing composite films.

Methylene Blue-Loaded NanoMOFs: Accumulation in Chlamydia trachomatis Inclusions and Light/Dark Antibacterial Effects

Metal-organic framework nanoparticles (nanoMOFs) are promising nanomaterials for biomedical applications. Some of them, including biodegradable porous iron carboxylates are proposed for encapsulation and delivery of antibiotics. Due to the high drug loading capacity and fast internalization kinetics, nanoMOFs are more beneficial for the treatment of intracellular bacterial infections compared to free antibacterial drugs, which poorly accumulate inside the cells because of the inability to cross membrane barriers or have low intracellular retention. However, nanoparticle internalization does not ensure their accumulation in the cell compartment that shelters a pathogen. This study shows the availability of MIL-100(Fe)-based MOF nanoparticles to co-localize with Chlamydia trachomatis, an obligate intracellular bacterium, in the infected RAW264.7 macrophages. Furthermore, nanoMOFs loaded with photosensitizer methylene blue (MB) exhibit complete photodynamic inactivation of C. trachomatis growth. Simultaneous infection and treatment of RAW264.7 cells with empty nanoMOFs resulted in a bacterial load reduction from 100 to 36% that indicates an intrinsic anti-chlamydial effect of this iron-containing nanomaterial. Thus, our findings suggest the use of iron-based nanoMOFs as a promising drug delivery platform, which contributes to antibacterial effect, for the treatment of chlamydial infections.

Impact of Crystallinity on Enzyme Orientation and Dynamics upon Biomineralization in Metal-Organic Frameworks

Aqueous-phase co-crystallization (also known as biomimetic mineralization or biomineralization) is a unique way to encapsulate large enzymes, enzyme clusters, and enzymes with large substrates in metal-organic frameworks (MOFs), broadening the application of MOFs as enzyme carriers. The crystallinity of resultant enzyme@MOF biocomposites, however, can be low, raising a concern about how MOF crystal packing quality affects enzyme performance upon encapsulation. The challenges to overcome this concern are (1) the limited database of enzyme performance upon biomineralization in different aqueous MOFs and (2) the difficulty in probing enzyme restriction and motion in the resultant MOF scaffolds, which are related to the local crystal packing quality/density, under the interference of the MOF backgrounds. We have discovered several new aqueous MOFs for enzyme biomineralization with varied crystallinity [Jordahl, D.; Armstrong, Z.; Li, Q.; Gao, R.; Liu, W.; Johnson, K.; Brown, W.; Scheiwiller, A.; Feng, L.; Ugrinov, A.; Mao, H.; Chen, B.; Quadir, M.; Pan, Y.; Li, H.; Yang, Z. Expanding the Library of Metal-Organic Frameworks (MOFs) for Enzyme Biomineralization. ACS Appl. Mater. Interfaces 2022, 14 (46), 51619-51629, DOI: 10.1021/acsami.2c12998]. Here, we address the second challenge by probing enzyme dynamics/restriction in these MOFs at the residue level via site-directed spin labeling (SDSL)-electron paramagnetic resonance (EPR) spectroscopy, a unique approach to determine protein backbone motions regardless of the background complexity. We encapsulated a model large-substrate enzyme, lysozyme, in eight newly discovered MOFs, which possess various degrees of crystallization, via aqueous-phase co-crystallization. Through the EPR study and simulations, we found rough connections between (a) enzyme mobility/dynamics and MOF crystal properties (packing quality and density) and (b) enzyme areas exposed above each MOF and their catalytic performance. This work suggests that protein SDSL and EPR can serve as an indicator of MOF crystal packing quality/density when biomineralized in MOFs. The method can be generalized to probing the dynamics of other enzymes on other solid surfaces/interfaces and guide the rational design of solid platforms (ca. MOFs) to customize enzyme immobilization.

Microgravimetric Modeling-A New Method for Extracting Adsorption Parameters of Functionalized MIL-101(Cr)

As a volatile air pollutant, formaldehyde can enter people's living environment through interior decoration, furniture and paint, causing serious harm to human health. Therefore, it is necessary to develop a sensor for the real-time detection of formaldehyde in low concentrations. According to the chemical interaction between amino groups and formaldehyde, a MIL-101(Cr) aminated-material-based formaldehyde cantilever sensor was prepared, of which ethylenediamine- functionalized MIL-101(Cr) named ED-MIL-101(Cr)) showed the best gas sensing performance. Using quasi-in situ infrared spectroscopy, ED-MIL-101(Cr) was found bound to formaldehyde through a Schiff base. The adsorption enthalpy of formaldehyde-bound ED-MIL-101(Cr) was -52.6 kJ/mol, which corresponds to weak chemical adsorption, so the material showed good selectivity. In addition, ED-MIL-101(Cr) has the most active sites, so its response value to formaldehyde is larger and it takes longer to reach saturation adsorption than bare MIL-101(Cr). Through the research on the gas sensing performance of functionalized MIL-101(Cr) material, we found that it has a strong application potential in the field of formaldehyde monitoring, and the material performance can be quantitatively and accurately evaluated through combining calculation and experimentation for understanding the gas sensing mechanism.

MOF-Assimilated High-Sensitive Organic Field-Effect Transistors for Rapid Detection of a Chemical Warfare Agent

The selective and rapid detection of trace amounts of highly toxic chemical warfare agents has become imperative for efficiently using military and civilian defense. Metal-organic frameworks (MOFs) are a class of inorganic-organic hybrid porous material that could be potential next-generation toxic gas sensors. However, the growth of a MOF thin film for efficiently utilizing the material properties for fabricating electronic devices has been challenging. Herein, we report a new approach to efficiently integrate MOF as a receptor through diffusion-induced ingress into the grain boundaries of the pentacene semiconducting film in the place of the most adaptive chemical functionalization method for sensor fabrication. We used bilayer conducting channel-based organic field-effect transistors (OFETs) as a sensing platform comprising CPO-27-Ni as the sensing layer, coated on the pentacene layer, showed a strong response toward sensing of diethyl sulfide, which is one of the stimulants of bis (2-chloroethyl) sulfide, a highly toxic sulfur mustard (HD). Using OFET as a sensing platform, these sensors can be a potential candidate for trace amounts of sulfur mustard detection below 10 ppm in real time as wearable devices for onsite uses.

Mesoporous-Structure MOF-14-Based QCM p-Xylene Gas Sensor

In this work, a facile synthesis method was adopted to synthesize MOF-14 with mesoporous structure. The physical properties of the samples were characterized by PXRD, FESEM, TEM and FT-IR spectrometry. By coating the mesoporous-structure MOF-14 on the surface of a quartz crystal microbalance (QCM), the fabricated gravimetric sensor exhibits high sensitivity to p-toluene vapor even at trace levels. Additionally, the limit of detection (LOD) of the sensor obtained experimentally is lower than 100 ppb, and the theoretical detection limit is 57 ppb. Furthermore, good gas selectivity and fast response (15 s) and recovery (20 s) abilities are also illustrated along with high sensitivity. These sensing data indicate the excellent performance of the fabricated mesoporous-structure MOF-14-based p-xylene QCM sensor. On the basis of temperature-varying experiments, an adsorption enthalpy of -59.88 kJ/mol was obtained, implying the existence of moderate and reversible chemisorption between MOF-14 and p-xylene molecules. This is the crucial factor that endows MOF-14 with exceptional p-xylene-sensing abilities. This work has proved that MOF materials such as MOF-14 are promising in gravimetric-type gas-sensing applications and worthy of future study.

Tactile Sensors: Hydroxyl Decorated Silver Metal-Organic Frameworks for Detecting Cr2O72-, MnO4-, Humic Acid, and Fe3+ Ions

Anionic, acidic, and metal ions are common contaminants in water and cause serious concerns for human and aquatic life. With the goal of rapid detection of analytes, we herein design a new array of ligand 5-(4H-1,2,4-triazol-4-yl)pyridin-3-ol-linked silver coordinated metal-organic frameworks Ag-MOFs as a promising sensor for Cr₂O₇^2-, MnO₄^-, humic acid (HA), and Fe³⁺ ions down to the micro level. Furthermore, as evidenced by luminescence, excitation-emission matrix (EEM) spectroscopic, and PXRD measurements, designed metal-organic frameworks (MOFs) can be fast, stable, and reusable for analyte detection in water.

In Silico High-Throughput Design and Prediction of Structural and Electronic Properties of Low-Dimensional Metal-Organic Frameworks

The advent of π-stacked layered metal-organic frameworks (MOFs), which offer electrical conductivity on top of permanent porosity and high surface area, opened up new horizons for designing compact MOF-based devices such as battery electrodes, supercapacitors, and spintronics. Permutation of structural building blocks, including metal nodes and organic linkers, in these electrically conductive (EC) materials, results in new systems with unprecedented and unexplored physical and chemical properties. With the ultimate goal of providing a platform for accelerated material design and discovery, here we lay the foundations for the creation of the first comprehensive database of EC-MOFs with an experimentally guided approach. The first phase of this database, coined EC-MOF/Phase-I, is composed of 1,057 bulk and monolayer structures built by all possible combinations of experimentally reported organic linkers, functional groups, and metal nodes. A high-throughput screening (HTS) workflow is constructed to implement density functional theory calculations with periodic boundary conditions to optimize the structures and calculate some of their most relevant properties. Because research and development in the area of EC-MOFs has long been suffering from the lack of appropriate initial crystal structures, all of the geometries and property data have been made available for the use of the community through an online platform that was developed during the course of this work. This database provides comprehensive physical and chemical data of EC-MOFs as well as the convenience of selecting appropriate materials for specific applications, thus accelerating the design and discovery of EC-MOF-based compact devices.

High-Performance Turn-On Fluorescent Metal-Organic Framework for Detecting Trace Water in Organic Solvents Based on the Excited-State Intramolecular Proton Transfer Mechanism

Simple, fast, and sensitive detection of trace water in organic solvents is an urgent requirement for chemical industries. Herein, combining the unusual excited-state intramolecular proton transfer (ESIPT) mechanism with the effective strategy of pore space partition, for the first time, we construct a powerful fluorescent metal-organic framework (SNNU-301) probe with excellent water stability. The SNNU-301 probe shows a remarkable performance for turn-on ESIPT-based fluorescence response to water in nine common organic solvents, exhibiting wide linear ranges, low limit of detection values, and ultrafast response, especially in dimethyl sulfoxide (0-5.2%; 0.011%, v/v; 110 s). The typical ESIPT-sensitive linker 2,5-dihydroxyterephthalate (DHBDC) imparts it with discriminative detection properties via enol-keto tautomerism, and light-responsive triangular tri(pyridin-4-yl)-amine (TPA) realizes pore space partition. The theoretical calculation gives an in-depth explanation about the proton transfer mechanism. Comparative experiments and GCMC simulation provide evidence that the synergy of the ESIPT process and TPA of the framework further boosts its performance effectively. Definitely, this work not only offers a promising candidate with fast detection speed, high sensitivity, excellent universality, and visual observation for the determination of water in organic solvents but also provides valuable guidance for the design of high-performance fluorescent probes.

New Application of Quartz Crystal Microbalance: A Minimalist Strategy to Extract Adsorption Enthalpy

The capture and separation of CO₂ is an important means to solve the problem of global warming. MOFs (metal-organic frameworks) are considered ideal candidates for capturing CO₂, where the adsorption enthalpy is a crucial indicator for the screening of materials. For this purpose, we propose a new minimalist solution using QCM (quartz crystal microbalance) to extract the CO₂ adsorption enthalpy on MOFs. Three kinds of MOFs with different properties, sizes and morphologies were employed to study the adsorption enthalpy of CO₂ using a QCM platform and a commercial gas sorption analyzer. A Gaussian simulation calculation and previously data reported were used for comparison. It was found that the measuring errors were between 5.4% and 6.8%, proving the reliability and versatility of our new method. This low-cost, easy-to-use, and high-accuracy method will provide a rapid screening solution for CO₂ adsorption materials, and it has potential in the evaluation of the adsorption of other gases.

A Dual-Mode NADH Biosensor Based on Gold Nanostars Decorated CoFe2 Metal-Organic Frameworks to Reveal Dynamics of Cell Metabolism

Nicotinamide adenine dinucleotide (NADH) is central to metabolism and implicated in various diseases. Herein, nanohybrids of gold nanostars and metal-organic frameworks are devised and demonstrated as a dual-mode NADH sensor, for which colorimetric detection is enabled by its peroxidase-like nanozyme property and Raman detection is realized by its surface-enhanced Raman scattering property with the detection limit as low as 28 pM. More importantly, this probe enables real-time SERS monitoring in living cells, providing a unique tool to investigate dynamic cellular processes involving NADH. Our experiments reveal that metabolism dynamics is accelerated by glucose and is much higher in cancerous cells. The SERS results can also be verified by the colorimetric detection. This sensor provides a new potential to detect biomarkers and their dynamics in situ.

Increased CO2 Affinity and Adsorption Selectivity in MOF-801 Fluorinated Analogues

The novel Zr^IV-based perfluorinated metal-organic framework (PF-MOF) [Zr₆O₄(OH)₄(TFS)₆] (ZrTFS) was prepared under solvent-free conditions using the commercially available tetrafluorosuccinic acid (H₂TFS) as a bridging ditopic linker. Since H₂TFS can be seen as the fully aliphatic and perfluorinated C₄ analogue of fumaric acid, ZrTFS was found to be isoreticular to zirconium fumarate (MOF-801). The structure of ZrTFS was solved and refined from X-ray powder diffraction data. Despite this analogy, the gas adsorption capacity of ZrTFS is much lower than that of MOF-801; in the former, the presence of bulky fluorine atoms causes a considerable window size reduction. To have PF-MOFs with more accessible porosity, postsynthetic exchange (PSE) reactions on (defective) MOF-801 suspended in H₂TFS aqueous solutions were carried out. Despite the different H₂TFS concentrations used in the PSE process, the exchanges yielded two mixed-linker materials of similar minimal formulae [Zr₆O₄(μ₃-OH)₄(μ₁-OH)_2.08(H₂O)_2.08(FUM)_4.04(HTFS)_1.84] (PF-MOF1) and [Zr₆O₄(μ₃-OH)₄(μ₁-OH)_1.83(H₂O)_1.83(FUM)_4.04(HTFS)_2.09] (PF-MOF2) (FUM^2- = fumarate), where the perfluorinated linker was found to fully replace the capping acetate in the defective sites of pristine MOF-801. CO₂ and N₂ adsorption isotherms collected on all samples reveal that both CO₂ thermodynamic affinity (isosteric heat of adsorption at zero coverage, Q_st) and CO₂/N₂ adsorption selectivity increase with the amount of incorporated TFS^2-, reaching the maximum values of 30 kJ mol^-1 and 41 (IAST), respectively, in PF-MOF2. This confirms the beneficial effect coming from the introduction of fluorinated linkers in MOFs on their CO₂ adsorption ability. Finally, solid-state density functional theory calculations were carried out to cast light on the structural features and on the thermodynamics of CO₂ adsorption in MOF-801 and ZrTFS. Due to the difficulties in modeling a defective MOF, an intermediate structure containing both linkers in the framework was also designed. In this structure, the preferential CO₂ adsorption site is the tetrahedral pore in the "UiO-66-like" structure. The extra energy stabilization stems from a hydrogen bond interaction between CO₂ and a hydroxyl group on the inorganic cluster.

Holistic Design Consideration of Metal-Organic Framework-Based Composite Membranes for Lithium-Sulfur Batteries

Metal-organic framework (MOF)-based membranes have received significant attention as separators for lithium-sulfur (Li-S) batteries because of their high porosities, well-defined and tailored structures, and other tunable features that are desirable for preventing the "shuttle effect" of soluble polysulfides. Because of the insulating nature of most MOFs, composite membranes are generally constructed by a combination of MOFs and electron-conductive materials. In this work, we examine the property-performance relation between MOF-based separators and Li-S batteries by systematically adjusting the electrical conductivity, thickness, and mass loading of the MOF-based composite. Beyond the commonly referenced trapping or blocking ability of MOFs toward polysulfides, we find that by fixing the thickness of the MOF-based composite coating layer (∼40 μm) on a Celgard membrane, the electrical conductivity of the MOF composite layer is of paramount importance compared with the physical/chemical trapping ability of polysulfides. However, the trapping ability of MOFs becomes indispensable when the thickness of the composite layer is small (e.g., ∼20 μm), indicating the synergetic effects of the adsorption and conversion capabilities of the thin composite layer. This work suggests the importance of a holistic design consideration for a MOF-based membrane for long-life and high-energy-density Li-S batteries.

Engineering the Interfacial Microenvironment via Surface Hydroxylation to Realize the Global Optimization of Electrochemical CO2 Reduction

The adsorption and activation of CO₂ on the electrode interface is a prerequisite and key step for electrocatalytic CO₂ reduction reaction (eCO₂ RR). Regulating the interfacial microenvironment to promote the adsorption and activation of CO₂ is thus of great significance to optimize overall conversion efficiency. Herein, a CO₂-philic hydroxyl coordinated ZnO (ZnO-OH) catalyst is fabricated, for the first time, via a facile MOF-assisted method. In comparison to the commercial ZnO, the as-prepared ZnO-OH exhibits much higher selectivity toward CO at lower applied potential, reaching a Faradaic efficiency of 85% at -0.95 V versus RHE. To the best of our knowledge, such selectivity is one of the best records in ZnO-based catalysts reported till date. Density functional theory calculations reveal that the coordinated surficial -OH groups are not only favorable to interact with CO₂ molecules but also function in synergy to decrease the energy barrier of the rate-determining step and maintain a higher charge density of potential active sites as well as inhibit undesired hydrogen evolution reaction. Our results indicate that engineering the interfacial microenvironment through the introduction of CO₂-philic groups is a promising way to achieve the global optimization of eCO₂ RR via promoting adsorption and activation of CO₂.

Synthesis of NMOF-5 Using Microwave and Coating with Chitosan: A Smart Biocompatible pH-Responsive Nanocarrier for 6-Mercaptopurine Release on MCF-7 Cell Lines

Cancer is one of the most difficult diseases to treat, threatening the lives of millions of people today. So far, various methods have been used to treat cancer, each having its drawbacks. One of these methods is treatment with anticancer drugs, which unfortunately have severe side effects. One of the causes of these complications is the nonspecific effects of anticancer drugs, which attack normal cells in addition to cancer cells and damage healthy tissues. In this study, we are trying to reduce the side effects and increase the efficacy of the drug by providing smart drug delivery. The metal-organic framework (MOF) was rapidly synthesized using a microwave method and at the nanoscale. The particle size of NMOF-5 was 18-20 nm, and its surface area was 2690 m²·g^-1. A chitosan polymer coating was formed on the nanocarrier after 6-mercaptopurine was introduced. The biocompatible nanocarrier exhibited a high capacity to adsorb the drug. The biocompatible nanocarrier slowly and uniformly released 96.78% of the drug in a simulated solution at pH 5 and 20.52% at pH 7.4. This showed that CS-6-MP-NMOF-5 released the drug smartly and pH-sensitively. The stability of the biocompatible nanocarrier was studied at different pH values and remained stable at pH 5 for up to 48 h. The toxicity study of the MCF-7 cell line at different concentrations for 24 h showed the excellent performance of the biocompatible nanocarrier compared to the free drug in terms of toxicity to breast cancer cells.

Programming a Metal-Organic Framework toward Excellent Hypergolicity

Exploring novel hypergolic fuels for modern space propulsion is highly desired. However, the analysis and understanding of the structure and hypergolic performance at the molecular level are still insufficient. To understand the factors that dictate hypergolicity, we conducted a comparative study on a series of metal-organic frameworks (MOFs) characterized by the same topology but with varied ligand structures. The ignition delay (ID) time trend was found to be imidazole < triazole < tetrazole, and the rapid ID time was 8 ms. By combining experimental studies and density functional theory (DFT) calculations, we found that propargyl and cyanoborohydride groups that functioned as dual hypergolic triggers contributed to the hypergolicity, and a distinct electronic structure was detrimental to ID time. The structure-performance relationships presented herein can potentially provide some fundamental insights into the field of developing high-performance hypergolic fuels.

Search for New Anode Materials for High Performance Li-Ion Batteries

Owing to an unmatched combination of power and energy density along with cyclic stability, the Li-ion battery has qualified itself to be the highest performing rechargeable battery. Taking both transportable and stationary energy storage requirements into consideration, Li-ion batteries indeed stand tall in comparison to any other existing rechargeable battery technologies. However, graphite, which is still one of the best performing Li-ion anodes, has specific drawbacks in fulfilling the ever-increasing energy and power density requirements of the modern world. Therefore, further research on alternative anode materials is absolutely essential. Equally important is the search for and enhanced use of right earth abundant materials for battery electrodes so as to bring down the costs of the battery systems. In this spotlight article, we discuss the current research progress in the area of alternative anode materials for Li-ion battery, putting our own research work over the past several years into perspective. Starting from conversion anode systems like oxides and sulfides, to insertion cum alloying systems like transition metal carbides, to molecularly engineered open framework systems like metal organic frameworks (MOFs), covalent organic frameworks (COFs), and organic-inorganic hybrid perovskites (OIHPs), this spotlight provides a complete essence of the recent developments in the area of alternative anodes. The possible and potential impact of these new anode materials is detailed and discussed here.

A Ni(II) Metal-Organic Framework with Mixed Carboxylate and Bipyridine Ligands for Ultrafast and Selective Sensing of Explosives and Photoelectrochemical Hydrogen Evolution

We report a Ni-MOF (nickel metal-organic framework), Ni-SIP-BPY, synthesized by using two linkers 5-sulfoisophthalic acid (SIP) and 4,4'-bipyridine (BPY) simultaneously. It displays an orthorhombic crystal system with the Ama2 space group: a = 31.425 Å, b = 19.524 Å, c = 11.2074 Å, α = 90°, β = 90°, γ = 90°, and two different types of nickel(II) centers. Interestingly, Ni-SIP-BPY exhibits excellent sensitivity (limit of detection, 87 ppb) and selectivity toward the 2,4,6-trinitrophenol (TNP)-like mutagenic environmental toxin in the pool of its other congeners via "turn-off" fluorescence response by the synergism of resonance energy transfer, photoinduced electron transfer, intermolecular charge transfer, π-π interactions, and competitive absorption processes. Experimental studies along with corroborated theoretical experimentation, vide density functional theory studies, shed light on determining the plausible mechanistic pathway in selective TNP detection, which is highly beneficial in the context of homeland security perspective. Along with the sensing of nitroaromatic explosives, the moderately low band gap and the p-type semiconducting behavior of Ni-SIP-BPY make it suitable as a photoanode material for visible-light-driven water splitting. Highly active surface functionalities and sufficient conduction band minima effectively reduce the water and result in a seven times higher photocurrent density under visible-light illumination.

Pillar-Layer Chiral MOFs as a Crystalline Platform for Circularly Polarized Luminescence and Single-Phase White-Light Emission

The construction of circularly polarized luminescence (CPL) materials with high porosity and high rigidity is still challenging. Herein, we propose a chiral reticular chemistry strategy to prepare the homochiral porous metal-organic frameworks (MOFs) as CPL-active materials. Two pairs of enantiomeric MOFs are synthesized through the self-assembly of chiral D/L-cam (DL-camphorates) and achiral fluorescent ligand TPB (1,2,4,5-tetra(pyridin-4-yl)benzene). The g_lum values of Cd-CMOF-D and Cd-CMOF-L were up to 0.010 and 0.009; the high g_lum values could be compared to those of the partially pure multicomponent self-assembly systems obtained by the complicated process. We further trace the generation and transfer of the hierarchical chirality from chiral molecule to 3D framework, demonstrating that the CPL was dominated by the original molecular chirality rather than the global chirality of the hierarchical structure. Moreover, the single-phase white-light materials with nearly ideal CIE coordinates (0.33, 0.33) were constructed through the introduction of dye emitters into Zn-CMOF (Zn-based chiral MOF). This work provided not only an insightful view of the chirality transfer and disappearance mechanism but also an efficient method for the preparation of the highly porous CPL materials.

Multifunctional Anthracene-Based Ni-MOF with Encapsulated Fullerenes: Polarized Fluorescence Emission and Selective Separation of C70 from C60

We report an anthracene-based Ni-MOF [Ni(II) metal-organic framework, {[Ni(μ₂-L)₂Cl₂]·x(C₆H₆)·y(MeOH)}_n (1), L = anthracene-9,10-diylbis(methylene)diisonicotinate] whose crystal structure reveals the presence of hexagonal channels with a pore size of 1.4 nm that can accommodate guests such as C₆₀ and C₇₀. Both confocal fluorescence and Raman microscopy results are in agreement with a homogeneous distribution of fullerenes throughout the single crystals of 1. Efficient energy transfer from 1 to the fullerenes was observed, which emitted partially polarized fluorescence emission. Stronger binding between 1 and C₇₀ versus C₆₀ was confirmed from HPLC analysis of the dissolved material and provides a basis for the selective retention of C₇₀ in liquid chromatography columns packed with 1.

pH-Responsive Oxygen and Hydrogen Peroxide Self-Supplying Nanosystem for Photodynamic and Chemodynamic Therapy of Wound Infection

The combination of photodynamic therapy (PDT) and chemodynamic therapy (CDT) has been continuously explored in the antibacterial aspect and has achieved more effective antibacterial effect than a single therapy. We design a pH-responsive O₂ and H₂O₂ self-supplying zeolitic imidazolate framework-67 (ZIF-67) nanosystem for PDT/CDT of wound infection. Under the acidic inflammatory conditions, ZIF-67 can degrade to produce Co²⁺ and release CaO₂ and graphene quantum dots (GQDs). The exposed CaO₂ reacted with water to generate H₂O₂ and O₂. The self-supplied O₂ alleviates hypoxia at the site of inflammation and enhances external light-initiated GQD-mediated PDT, while H₂O₂ was catalyzed by endogenous Co²⁺ to produce hydroxyl radicals for Co²⁺-triggered CDT. In vitro and in vivo experiments confirm that CaO₂/GQDs@ZIF-67 has a combined PDT/CDT effect. The antibacterial mechanism indicates that bacteria post-treated with CaO₂/GQDs@ZIF-67 may be sterilized by reactive oxygen species-mediated oxidative stress and the leakage of bacterial contents. The experiments also find that CaO₂/GQDs@ZIF-67 may activate the immune response and enhance the therapeutic effect by activating the cyclic GMP-AMP synthase-stimulator of interferon genes signaling pathway.

Impact of the Structural Modification of Diamondoid Cd(II) MOFs on the Nonlinear Optical Properties

A change in the degree of interpenetration (DOI) in metal-organic frameworks (MOFs) prompted by heat, pressure, or exchange of solvents is a fascinating phenomenon that can potentially impact the functional properties of MOFs. Structural transformation involving two noncentrosymmetric MOFs with different DOIs provides a rare opportunity to manipulate their optical properties. Herein, we report an unusual single-crystal-to-single-crystal (SCSC) transformation of a noncentrosymmetric 7-fold interpenetrated diamondoid (dia) Cd(II) MOF into another noncentrosymmetric but 8-fold interpenetrated dia MOF upon the removal of guest solvents. A hydrogen-bond network formed between the lattice solvents and linker trans-2-(4-pyridyl)-4-vinylbenzoate (pvb) in a 7-fold interpenetrated noncentrosymmetric MOF results in a significant increase in the two-photon absorption cross-section (11 times) as compared to that in the desolvated 8-fold interpenetrated MOF. Also, an increase in the DOI in the noncentrosymmetric crystals strengthened the π···π interaction between the individual diamondoid networks and enhanced the second-order nonlinear optical (NLO) coefficient (deff) by 4.5 times. These results provide a way to manipulate the optical properties of MOFs using a combined strategy of the formation of hydrogen bonds and interpenetration for access to tunable single-crystal NLO devices in an SCSC manner. By changing the experimental conditions, another dia Cd(II) MOF with 4-fold interpenetration can be isolated. In this centrosymmetric MOF, the olefin groups in the backbone of the ligand (pvb) undergo a [2 + 2] cycloaddition reaction quantitatively under UV light but in a non-SCSC fashion.

Temperature-Dependent Nitrous Oxide/Carbon Dioxide Preferential Adsorption in a Thiazolium-Functionalized NU-1000 Metal-Organic Framework

Solvent-assisted ligand incorporation (SALI) of the ditopic linker 5-carboxy-3-(4-carboxybenzyl)thiazolium bromide [(H₂PhTz)Br] into the zirconium metal-organic framework NU-1000 [Zr₆O₄(OH)₈(H₂O)₄(TBAPy)₂, where NU = Northwestern University and H₄TBAPy = 1,3,6,8-tetrakis(p-benzoic-acid)pyrene], led to the SALIed NU-1000-PhTz material of minimal formula [Zr₆O₄(OH)₆(H₂O)₂(TBAPy)₂(PhTz)]Br. NU-1000-PhTz has been thoroughly characterized in the solid state. As confirmed by powder X-ray diffraction, this material keeps the same three-dimensional architecture of NU-1000 and the dicarboxylic extra linker bridges adjacent [Zr₆] nodes ca. 8 Å far apart along the crystallographic c-axis. The functionalized MOF has a BET specific surface area of 1560 m²/g, and it is featured by a slightly higher thermal stability than its parent material (T_dec = 820 vs. 800 K, respectively). NU-1000-PhTz has been exploited for the capture and separation of two pollutant gases: carbon dioxide (CO₂) and nitrous oxide (N₂O). The high thermodynamic affinity for both gases [isosteric heat of adsorption (Q_st) = 25 and 27 kJ mol^-1 for CO₂ and N₂O, respectively] reasonably stems from the strong interactions between these (polar) "stick-like" molecules and the ionic framework. Intriguingly, NU-1000-PhTz shows an unprecedented temperature-dependent adsorption capacity, loading more N₂O in the 298 K ≤ T ≤ 313 K range but more CO₂ at temperatures falling out of this range. Grand canonical Monte Carlo simulations of the adsorption isotherms confirmed that the preferential adsorption sites of both gases are the triangular channels (micropores) in close proximity to the polar pillar. While CO₂ interacts with the thiazolium ring in an "end-on" fashion through its O atoms, N₂O adopts a "side-on" configuration through its three atoms simultaneously. These findings open new horizons in the discovery of functional materials that may discriminate between polluting gases through selective adsorption at different temperatures.

Recent Advances in Emerging Metal- and Covalent-Organic Frameworks for Enzyme Encapsulation

Enzyme catalysis enables complex biotransformation to be imitated. This biomimetic approach allows for the application of enzymes in a variety of catalytic processes. Nevertheless, enzymes need to be shielded by a support material under challenging catalytic conditions due to their intricate and delicate structures. Specifically, metal-organic frameworks and covalent-organic frameworks (MOFs and COFs) are increasingly popular for use as enzyme-carrier platforms because of their excellent tunability in structural design as well as remarkable surface modification. These porous organic framework capsules that host enzymes not only protect the enzymes against harsh catalytic conditions but also facilitate the selective diffusion of guest molecules through the carrier. This review summarizes recent progress in MOF-enzyme and COF-enzyme composites and highlights the pore structures tuned for enzyme encapsulation. Furthermore, the critical issues associated with interactions between enzymes and pore apertures on MOF- and COF-enzyme composites are emphasized, and perspectives regarding the development of high-quality MOF and COF capsules are presented.

Targeting Enrichment and Correlation Studies of Glutathione and Homocysteine in IgAVN Patient Urine Based on a Core-Shell Zr-Based Metal-Organic Framework

Aminothiols are closely related to chronic kidney disease, but little is known regarding levels of related aminothiols in the urine of immunoglobulin A vasculitis with nephritis (IgAVN) patients. Herein, a well-defined core-shell Zr-based metal-organic framework (Zr-MOF) composite SiO₂@50Benz-Cys was constructed as a mercury ion affinity material via a solvent-assisted ligand exchange strategy for the selective extraction and enrichment of low-concentration aminothiols in IgAVN patient urine. SiO₂@50Benz-Cys was competent to enrich the total glutathione (GSH) and total homocysteine (Hcy) in virtue of the excellent affinity after chelation with mercury ions. The extraction efficiencies were closely related to the pH, dithiothreitol amount, and the dose of functional Zr-MOF. Coupled with HPLC-MS/MS in optimized conditions, GSH and Hcy were determined with low detection limits of 0.5 and 1 nmol L^-1, respectively. The recoveries of GSH and Hcy for the urine sample at three spiked levels were in the range of 85.3-105% and 79.5-103%, which showed good precision and accuracy. Benefiting from the matrix interference elimination in the process of extraction, the simultaneous detection of aminothiols in the urine of the healthy group and immunoglobulin A vasculitis (IgAV) and IgAVN patients was successfully carried out, suggesting that the Zr-MOF and the robust method together provided a potential application in the analysis of urinary biomolecules. The analysis of variance (ANOVA) showed that the levels of GSH and Hcy had significant differences between the patients and the control. This work is very valuable as it provides a better understanding of concentration alterations of GSH and Hcy in urine involved with IgAVN for clinical research.

Engineering Near-Infrared-Excitable Metal-Organic Framework for Tumor Microenvironment Responsive Therapy

Luminescent metal-organic frameworks (MOFs), which incorporate some guest luminescent molecules/ions into MOFs, have attracted extensive attention because of their exceptional optical properties. However, traditional luminescent MOFs are mainly responsive to ultraviolet (UV) or visible light, which has limited their bioapplications due to the restrained tissue penetration depths. In this study, we have constructed a diagnostic nanoplatform UCNP@MOF consisting of upconverting metal-organic frameworks, which combine the photo-upconverting characteristics of the upconversion nanoparticles (UCNPs) with the unique physicochemical properties of Al-MOFs. Specifically, the core-shell structured UCNP@MOF nanocomposites were prepared by poly(vinylpyrrolidone) (PVP)-regulated nucleation of Al-MOF layer on the UCNP surface. When excited by a 980 nm laser light, the green signal released from UCNPs can trigger the photosensitive Al-MOFs to produce a large amount of singlet oxygen (¹O₂) for photodynamic therapy (PDT). Meanwhile, the anticancer drug, doxorubicin hydrochloride (DOX), was further incorporated into the porous structures of Al-MOFs and demonstrated the pH-responsive drug release behavior. Our results show that the near-infrared (NIR) light-induced PDT with chemotherapy (CMT) exhibits excellent antitumor effects. It is believed that the present work highlights the potential of the combination of UCNPs and MOFs and holds great promise for biomedical applications.

Recyclable and Magnetically Functionalized Metal-Organic Framework Catalyst: IL/Fe3O4@HKUST-1 for the Cycloaddition Reaction of CO2 with Epoxides

A recyclable and magnetic nanocomposite catalyst (IL/Fe₃O₄@HKUST-1) was synthesized via grafting ionic liquid (IL) [AEMIm]BF₄ into magnetically functionalized metal-organic framework Fe₃O₄@HKUST-1 in a water-ethanol media. The properties of IL/Fe₃O₄@HKUST-1 were fully characterized by powder X-ray diffraction, electron microscopy, Fourier-transform infrared spectroscopy, nitrogen adsorption-desorption, density-functional theory, and a magnetic property measurement system. IL/Fe₃O₄@HKUST-1 showed high activity in the solvent-free cycloaddition of CO₂ with epoxides under mild conditions. Furthermore, the catalyst can be easily separated from the reaction mixture, and the recycled catalyst maintained high performance for several cycles. The synergistic effect of the Lewis acid and base sites in IL/Fe₃O₄@HKUST-1 contributes to its greater reactivity than individual IL or HKUST-1.

Novel Mn-/Co-Nx Moieties Captured in N-Doped Carbon Nanotubes for Enhanced Oxygen Reduction Activity and Stability in Acidic and Alkaline Media

Fe-N-C-based electrocatalysts have been developed as an encouraging substitute compared to their expensive Pt-containing equivalents for the oxygen reduction reaction (ORR). However, they still face major durability challenges from the in- situ production of Fenton radicals. Therefore, the synthesis of Fe-free ORR catalysts is among the emerging concerns. Herein, we have precisely applied a multistep heating strategy to produce mesoporous N-doped carbon nanostructures with Mn-/Co-N_x dual moieties from mixed-metal zeolitic imidazolate frameworks (ZIFs). It is found that their unique structure, with dual-metallic active sites, not only offers a high electrochemical performance for the ORR (E_1/2 = 0.83 V vs reversible hydrogen electrode (RHE) in acid media), but also enhances the operational durability of the catalyst after 20 000 cycles with 97% of retention and very low H₂O₂ production (<5%) in 0.1 M HClO₄. In addition, the catalyst performs well toward the ORR also in alkaline solution (exhibiting E_1/2 = 0.90 V and 30 000 cyclic stability).

A New Molecular Recognition Concept: Multiple Hydrogen Bonds and Their Optically Triggered Proton Transfer in Confined Metal-Organic Frameworks for Superior Sensing Element

We report a new sensing mechanism based on an indium-dihydroxyterephthalic acid metal-organic framework (MOF, SNNU-153), in which the spatially fitted analyte-MOF hydrogen-bond (H-bond) formation provides selective recognition while the analyte-H-bond assisted excited-state intramolecular proton transfer (ESIPT) and the resulting ratiometric emission act as a superior signal transducer with ultrafast response. The synergy of ESIPT signal transduction and confined MOF pore enables the SNNU-153 sensor selectively sensing hydrazine even among nitrogen-containing hydride analogs such as NH₃, NH₂OH, and (Me)₂NNH₂. The key of H-bond and associated ESIPT was further counter evidenced by an indium-2,5-dimethoxyterephthalic acid MOF (SNNU-152), where the hydroxyl protons were removed by methylation, showing near inertness to N₂H₄. The new molecular recognition concept thus makes SNNU-153 a powerful N₂H₄ sensor, which should be far-reaching to other sensing elements.

Rapid Exciton Migration and Amplified Funneling Effects of Multi-Porphyrin Arrays in a Re(I)/Porphyrinic MOF Hybrid for Photocatalytic CO2 Reduction

A porphyrinic metal-organic framework (PMOF) known as PCN-222(Zn) was chemically doped with a molecular Re(I) catalyst-bearing carboxylate anchoring group to form a new type of metal-organic framework (MOF)-Re(I) hybrid photocatalyst. The porphyrinic MOF-sensitized hybrid (PMOF/Re) was prepared with an archetypical CO₂ reduction catalyst, (L)Re^I(CO)₃Cl (Re(I); L = 4,4'-dicarboxylic-2,2'-bipyridine), in the presence of 3 vol % water produced CO with no leveling-off tendency for 59 h to give a turnover number of ≥1893 [1070 ± 80 μmol h^-1 (g MOF)^-1]. The high catalytic activity arises mainly from efficient exciton migration and funneling from photoexcited porphyrin linkers to the peripheral Re(I) catalytic sites, which is in accordance with the observed fast exciton (energy) migration (≈1 ps) in highly ordered porphyrin photoreceptors and the effective funneling into Re(I) catalytic centers in the Re(I)-doped PMOF sample. Enhanced catalytic performance is convincingly supported by serial photophysical measurements including decisive Stern-Volmer interpretation.

A Green-Emission Metal-Organic Framework-Based Nanoprobe for Imaging Dual Tumor Biomarkers in Living Cells

The modular nature of metal-organic frameworks (MOFs) permits their tunable structure and function for target application, such as in biomedicine. Herein, a green-emission Zr(IV)-MOF (BUT-88) was constructed from a customized luminescent carbazolyl ligand. BUT-88 represents the first bcu-type MOF with both organic linker and metal node in eight connections and shows medium-sized pores, rich accessible linking sites, and good water stability and biocompatibility. In virtue of these merits, BUT-88 was then fabricated into a MOF-based fluorescent nanoprobe, drDNA-BUT-88. Using it, the live-cell imaging of dual tumor biomarkers was achieved for the first time upon a MOF-based probe, offering enhanced detection precision in early cancer diagnosis. Particularly, the probe showed efficient ratiometric fluorescent sensing toward the cytoplasmic biomarker microRNA-21, further improving the detection accuracy at the cellular level. In this work, the elaborate combination of MOF engineering and the fluorescent detection technique has contributed a facile biosensing platform, unlocking more possibilities of MOF chemistry.

Continuous Flow Composite Membrane Catalysts for Efficient Decomposition of Chemical Warfare Agent Simulants

Continuous and safe decomposition of chemical warfare agents (CWAs) is a critical requirement to protect both soldiers and citizens and to eliminate the stockpiles after the cold war. The Zr-based metal-organic framework (Zr-MOF) has been known as the most effective catalyst for decomposing CWAs, especially the most fatal nerve agents, however, its low processability due to the powder form limits its expansion to actual military applications. To this end, the composite membrane catalysts (CMCs) comprising the Zr-MOF (UiO-66 catalyst) and nylon 6 nanofiber (porous supporter) are developed by the simple integration of electrospray and electrospinning, resulting in selective immobilization of UiO-66 on the surface of the nylon 6 nanofibers. These strategical benefits of CMCs gave super catalytic durability including recyclability over five times without decreasing the catalytic activity for the decomposition of methyl paraoxon (MPO), a simulant of the nerve agent, in the presence of N-ethylmorpholine (N-EM), which was not achieved in the original particulate UiO-66. Because of the excellent physical and chemical stabilities of CMCs, the CMC with 56 wt % of UiO-66 (CMC56) decomposed 198 g of MPO within an hour in the continuous flow system with a flow rate of 21.6 mL h^-1. This study highlights the important strategies in designing the feasible membrane-type catalysts with superior catalytic activity and robust durability for decomposing CWAs in the continuous flow system.

Catalytic Activity, Stability, and Loading Trends of Alcohol Dehydrogenase Enzyme Encapsulated in a Metal-Organic Framework

Recently, it has been shown that enzyme encapsulation inside metal-organic frameworks (MOFs) can increase enzyme activity and serve as protection from adverse environmental conditions. Little is understood about how the enzymes move into and are held inside the MOFs although it is believed that intermolecular forces between the MOF and the enzyme cause it to be held in place. If this process can be better understood, it can have dramatic implications on the cost-effectiveness and implementation of enzyme-MOF complexes. This is of specific importance in the medical sector for protein therapy and the industrial sector where enzyme use is expected to increase. Herein, we synthesized alcohol dehydrogenase (ADH) and PCN-333 to study encapsulation, stability, and enzyme activity to expand the knowledge of our field and offer a potential improvement to a synthetic route for biofuel synthesis. From this, we found a correlation between the concentration of a buffer and the loading of an enzyme, with surprising loading trends. We conclude that the buffer solution decreases interactions between the enzyme and MOF, supporting conventional theory and allowing it to penetrate deeper into the structure causing higher enzyme loading while allowing for excellent stability over time at various pH values and temperatures and after multiple reactions. We also observe new trends such as a rebounding effect in loading and "out-of-bounds" reactions.

Hydrophobic MOFs@Metal Nanoparticles@COFs for Interfacially Confined Photocatalysis with High Efficiency

Converting solar energy to chemical energy via photocatalysis has attracted increasing interest. Simultaneously realizing efficient charge separation and fast reactant/product diffusion/transport is highly significant for improving the photocatalytic activity, which however is difficult. Herein, we reported an interfacially confined strategy by constructing interfacial pores as nanoreactors between metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) with controlled surface wettability for efficient photocatalysis. In the sandwich Ti-MOFs@Pt@DM-LZU1, interfacial pores formed between Ti-MOF@Pt and DM-LZU1, in which Pt nanoparticles (NPs) were encapsulated. The presence of Pt facilitates the charge separation on the photoactive Ti-MOF, while the hydrophobic porous DM-LZU1 shell promotes reactant enrichment. Interfacial pores acting as nanoreactors ensure fast electron and mass transport between the active Pt NPs and the concentrated reactants, leading to high photocatalytic activity. This work presents a new concept for the design of various photocatalysts with considerable activity.

Isostructural MOFs with Higher Proton Conductivity for Improved Oxygen Evolution Reaction Performance

Here we synthesized two new isostructural MOFs (FJU-82-Co/FJU-82-Zn) and first observed that tuning of the proton conductivity may provide an effective strategy to improve the electrocatalytic OER perfomances of isostructural crystalline MOF materials. The conductivity value for FJU-82-Co is 7.40 × 10^-5 S cm^-1, which is 127-fold that for FJU-82-Zn with 5.80 × 10^-7 S cm^-1 at 60 °C and 98% RH, while the overpotential of FJU-82-Co is 0.57 V at 1 mA cm^-2, which is better than that of FJU-82-Zn with 1.17 V.

Mimic of Ferroalloy To Develop a Bifunctional Fe-Organic Framework Platform for Enhanced Gas Sorption and Efficient Oxygen Evolution Electrocatalysis

It is well-known that the formation of ferroalloy with the addition of the second or third metal during the steel-making process usually can improve the performance of the iron. Inspired by ferroalloy materials, it is speculated that the pore environment, framework charge, and catalytic properties of metal-organic frameworks (MOFs) could be optimized dramatically via the introduction of ferroalloy-like inorganic building blocks. However, different to ferroalloy, the accurate integration of different metals into one MOF platform is still challenging. Herein, taking advantages of the good compatibility for metals in trigonal prismatic trinuclear cluster, a series of Fe-based alloy-like [M₃O(O₂C)₆] motifs (M₃ = Fe₃, Fe_1.5Ni_1.5, Fe_1.5Co_1.5, Fe_1.5Ti_1.5, FeCoNi, and FeTiCo) are successfully generated, which further lead to a robust Fe-MOF material family (SNNU-5s). These multicomponent MOFs not only provide a good chance to explore the impact of pore environment on gas adsorption/separation but also offer an opportunity to the efficient electrocatalytic reaction directly. Accordingly, compared with the SNNU-5-Fe parent structure, the pore characters of heterometallic SNNU-5 MOFs are clearly regulated by the type of alloy-like building blocks. SNNU-5-FeTi displays more superior gas separation performance for CO₂/CH₄, C₂H₂/CH₄, C₂H₄/CH₄, and C₂H₂/CO₂ gas mixtures. What is more, benefited from the multimetallic active sites and their catalytic synergy, FeCoNi-ternary alloy-like cluster-based SNNU-5 MOF material exhibits an exceptional oxygen evolution reaction activity in aqueous solution at pH = 13, which delivers a low overpotential (η_j=10 = 317 mV), a fast reaction kinetics (Tafel slope = 37 mV dec^-1), and excellent catalytic stability. This facile multialloy-like building block strategy holds promise to accurately design and improve the performance of MOFs, as well as open an avenue to understand the related mechanisms.

Metal-Organic Frameworks as a Theranostic Nanoplatform for Combinatorial Chemophotothermal Therapy Adapted to Different Administration

With the rapid development of nanotechnology, nanomaterial drug delivery systems have provided an alternative for designing controllable drug delivery systems due to their spatiotemporally controllable properties. As a new type of porous material, metal-organic frameworks (MOFs) have been widely used in biomedical applications, especially drug delivery systems, owing to their tunable pore size, high surface area and pore volume, and easy surface modification. Here, we demonstrate an MOF as a theranostic nanoplatform to combine drug therapy and phototherapy after labeling targeting peptide iRGD. The micropore Fe-MOF was used as MRI agents for locating tumors and as nanocarriers to upload chemotherapeutic drugs. Moreover, MOF showed excellent targeting performance under different administration including intravenous injection for breast cancer and local instillation for bladder cancer. Notably, when irradiated with an 808 nm laser, the agent demonstrates the high efficacy of photothermal therapy and heat release efficiency of the drug around the tumor site. This combination therapy provides an alternative drug administration method and can be adapted to a series of cancer cell types and molecular targets associated with disease progression.

Partial Sulfurization of a 2D MOF Array for Highly Efficient Oxygen Evolution Reaction

A feasible strategy for the in situ growth of two-dimensional (2D) [Ni₃(OH)₂(1,4-BDC)₂-(H₂O)₄]·2H₂O (Ni-BDC; 1,4-BDC = 1,4-benzenedicarboxylate) and the subsequent partial sulfurization treatment for the decoration of nickle sulfide (NiS) is developed. The fabricated hierarchically structured Ni-BDC@NiS as a synergistic electrocatalyst shows extremely high activity toward the oxygen evolution reaction (OER). The optimal Ni-BDC@NiS catalyst acquires a current density of 20 mA cm^-2 at a lower overpotential of 330 mV and low Tafel slope of 62 mV dec^-1, outperforming most previously reported Ni-based sulfide catalysts. Clearly, the combination of the NiS and Ni-BDC array contributed to the improvement of electron transfer, promotion of water adsorption, and increase of rich active species. In addition, the in situ created hierarchical structure not only affords feasible access for mass transport but also strengthens structural integrity, contributing to efficient and stable OER performance. This general and effective strategy anchoring conductive active species on a porous metal-organic framework (MOF) thus provides an efficient way to fabricate synergistic electrocatalysts for the OER.

Intracellular Imaging of Glutathione with MnO2 Nanosheet@Ru(bpy)32+-UiO-66 Nanocomposites

Fluorescent detection of glutathione (GSH) in the living system has attracted much attention, but current fluorescent probes are usually exposed to the exterior environment, leading to photobleaching and premature leakage and subsequently limiting the sensitivity and photostability. Herein, luminescent metal-organic frameworks [Ru(bpy)₃²⁺ encapsulated in UiO-66] coated with manganese dioxide nanosheets [MnO₂ NS@Ru(bpy)₃²⁺-UiO-66] were prepared by an in situ growth method and further explored to construct a GSH-switched fluorescent sensing platform. Because of the splendid fluorescence quenching ability, special probe leakage blocking role and distinguished recognition of the MnO₂ NS, and the improved fluorescence of Ru(bpy)₃²⁺ by UiO-66, a low background, highly sensitive and selective detection of GSH with a low limit of detection as 0.28 μM was realized. At the same time, the preparation of MnO₂ NS@Ru(bpy)₃²⁺-UiO-66 nanocomposites is simple and less toxic, and there was no notable loss of cell survivability after being exposed to MnO₂ NS@Ru(bpy)₃²⁺-UiO-66 below the concentrations of 120 μg mL^-1 for 24 h. Consequently, the results coming from this effort suggest that the new sensing platform will have a great potential in the detection of GSH in living cells.

Core-Shell CoNi@Graphitic Carbon Decorated on B,N-Codoped Hollow Carbon Polyhedrons toward Lightweight and High-Efficiency Microwave Attenuation

Lightweight and high-efficiency microwave attenuation are two major challenges in the exploration of carbon-based absorbers, which can be achieved simultaneously by manipulating their chemical composition, microstructure, or impedance matching. In this work, core-shell CoNi@graphitic carbon decorated on B,N-codoped hollow carbon polyhedrons has been constructed by a facile pyrolysis process using metal-organic frameworks as precursors. The B,N-codoped hollow carbon polyhedrons, originated from the calcination of Co-Ni-ZIF-67, are composed of carbon nanocages and BN domains, and CoNi alloy is encapsulated by graphitic carbon layers. With a filling loading of 30 wt %, the absorber exhibits a maximum R_L of -62.8 dB at 7.2 GHz with 3 mm and the effective absorption bandwidth below -10 dB remarkably reaches as strong as 8 GHz when the thickness is only 2 mm. The outstanding microwave absorption performance stems from the hollow carbon polyhedrons and carbon nanocages with interior cavities, the synergistic coupling effect between the abundant B-C-N heteroatoms, the strong dipolar/interfacial polarizations, the multiple scatterings, and the improved impedance matching. This study demonstrates that the codoped strategy provides a new way for the rational design of carbon-based absorbers with lightweight and superior microwave attenuation.