Single‐Crystal‐to‐Single‐Crystal Transformation of a Europium(III) Metal–Organic Framework Producing a Multi‐responsive Luminescent Sensor

A sensor with a red‐emission signal is successfully obtained by the solvothermal reaction of Eu³⁺ and heterofunctional ligand bpydbH₂ (4,4′‐(4,4′‐bipyridine‐2,6‐diyl) dibenzoic acid), followed by terminal‐ligand exchange in a single‐crystal‐to‐single‐crystal transformation. As a result of treatments both before and after the metal–organic framework formation, accessible Lewis‐base sites and coordinated water molecules are successfully anchored onto the host material, and they act as signal transmission media for the recognition of analytes at the molecular level. This is the first reported sensor based on a metal–organic framework (MOF) with multi‐responsive optical sensing properties. It is capable of sensing small organic molecules and inorganic ions, and unprecedentedly it can discriminate among the homologues and isomers of aliphatic alcohols as well as detect highly explosive 2,4,6‐trinitrophenol (TNP) in water or in the vapor phase. This work highlights the practical application of luminescent MOFs as sensors, and it paves the way toward other multi‐responsive sensors by demonstrating the incorporation of various functional groups into a single framework.     

Metal Doped Core–Shell Metal‐Organic Frameworks@Covalent Organic Frameworks (MOFs@COFs) Hybrids as a Novel Photocatalytic Platform

Metal doped core–shell Metal‐Organic Frameworks@Covalent Organic Frameworks (MOFs@COFs) are presented as a novel platform for photocatalysis. A palladium (Pd) doped MOFs@COFs in the form of Pd/TiATA@LZU1 shows excellent photocatalytic performance for tandem dehydrogenation and hydrogenation reactions in a continuous‐flow microreactor and a batch system, indicating the great potential of the metal doped MOFs@COFs as a multifunctional platform for photocatalysis. Explanations for the performance enhancement are elucidated. An integrated dual‐chamber microreactor coupled with the metal doped MOFs@COFs is introduced to demonstrate a concept of an intensified green photochemical process, which can be broadly extended to challenging liquid–gas tandem and cascade reactions.     

Zeolitic Imidazole Framework: Metal–Organic Framework Subfamily Members for Triboelectric Nanogenerators

Zeolitic imidazole framework (ZIF), a subfamily of metal–organic framework (MOF), offers excellent chemical and thermal stability in addition to other MOF advantages. The triboelectric series predominantly consist of few metals and mainly polymers that are not suitable for the development of sensors with high selectivity and specificity. The development of multifunctional, tunable materials is of utmost importance for extending the applications of a triboelectric nanogenerator (TENG). The TENG based on the ZIF subfamily materials (ZIF‐7, ZIF‐9, ZIF‐11, and ZIF‐12) is reported here. The surface roughness, structural, morphological, and surface potential analysis reveals the detailed characteristics of the ZIF family members. The ZIFs and Kapton are used as triboelectric layers for the ZIF‐TENG fabrication. The device is analyzed in detail for its electrical performance (voltage, current, charge, stability, load matching analysis, and capacitor charging). The ZIF‐7 TENG generates the highest output of 60 V and 1.1 µA in vertical contact‐separation mode. Finally, various low‐power electronics are successfully driven with the capacitor charged by the output of the ZIF‐7 TENG.     

Compartmentalization within Self‐Assembled Metal–Organic Framework Nanoparticles for Tandem Reactions

Compartmentalization is an essential feature found in living cells to ensure multiple biological processes occur without being affected by undesired external influences. Here, compartmentalized systems are developed based on the self‐assembly of metal–organic framework (MOF) nanoparticles into multifunctional MOF capsules (MOF‐Cs). Such MOF‐Cs have the capability of controlling molecular transportation and protecting interior microenvironment, thus making tandem reaction along trajectories to desired products. First of all, MOF‐Cs present controlled molecular transportation derived from molecular sieving property of MOFs. Second, MOF‐Cs can protect the encapsulated cargoes from denaturation and maintain their catalytic activity. Third, MOF‐Cs can provide spatial segregation for incompatible species and facilitate communication between these compartments to perform tandem reactions. These compartmentalized structures offer new views in the transportation, microreactor, and biotechnology.     

Conductive Metal–Organic Framework Nanowire Array Electrodes for High‐Performance Solid‐State Supercapacitors

The application of conventional metal–organic frameworks (MOFs) as electrode materials in supercapacitors is largely hindered by their conventionally poor electrical conductivity. This study reports the fabrication of conductive MOF nanowire arrays (NWAs) and the application of them as the sole electrode material for solid‐state supercapacitors. By taking advantage of the nanostructure and making full use of the high porosity and excellent conductivity, the MOF NWAs in solid‐state supercapacitor show the highest areal capacitance and best rate performance of all reported MOF materials for supercapacitors, which is even comparable to most carbon materials.     

Fluorous Metal–Organic Frameworks and Nonporous Coordination Polymers as Low‐κ Dielectrics

A fluorous metal–organic framework [Cu(FBTB)(DMF)] (FMOF‐3) [H₂FBTB = 1,4‐bis(1‐H‐tetrazol‐5‐yl)tetrafluorobenzene] and fluorous nonporous coordination polymer [Ag₂(FBTB)] (FN‐PCP‐1) are synthesized and characterized as for their structural, thermal, and textural properties. Together with the corresponding nonfluorinated analogues lc‐[Cu(BTB)(DMF)] and [Ag₂(BTB)], and two known (super)hydrophobic MOFs, FMOF‐1 and ZIF‐8, they have been investigated as low‐dielectric constant (low‐κ) materials under dry and humid conditions. The results show that substitution of hydrogen with fluorine or fluoroalkyl groups on the organic linker imparts higher hydrophobicity and lower polarizability to the overall material. Pellets of FMOF‐1, FMOF‐3, and FN‐PCP‐1 exhibit κ values of 1.63(1), 2.44(3), and 2.57(3) at 2 × 10⁶ Hz, respectively, under ambient conditions, versus 2.94(8) and 3.79(1) for lc‐[Cu(BTB)(DMF)] and [Ag₂(BTB)], respectively. Such low‐κ values persist even upon exposure to almost saturated humidity levels. Correcting for the experimental pellet density, the intrinsic κ for FMOF‐1 reaches the remarkably low value of 1.28, the lowest value known to date for a hydrophobic material.     

Solvent‐Mediated Reconstruction of the Metal–Organic Framework HKUST‐1 (Cu3(BTC)2)

The principle of integral metal–organic framework (MOF) reconstruction is demonstrated for differently degraded HKUST‐1 via a facile, one‐step, solvent‐assisted treatment. Controlled MOF degradation by exposure to 77% humidity, liquid water, and diluted hydrochloric acid produces a mixture of non‐porous crystalline hybrid materials containing protonated linker and copper‐oxo species, which are then reconstructed back into high‐quality HKUST‐1 by contacting them with ethanol. X‐ray diffraction and sorption kinetics reveal a true memory effect of the system from completely degraded materials. The reconstruction approach is consequently extrapolated to gas‐ and liquid‐phase treatments in a fixed‐bed reactor with ethanol and ethanol/water mixtures for use in CO₂ capture from a simulated pre‐combustion gas stream. Up to a maximum of 94% porosity and 85% CO₂ sorption capacity can be recovered from a steamed material. A degradation‐reconstruction model is put forward based on X‐ray diffraction observations and structural analyses, microscopy, N₂ sorption, thermogravitry–mass spectrometry and IR spectroscopy observations, particularly elucidating the influence of various degradation pathways on the reconstruction.     

Boronic Acid Decorated Defective Metal–Organic Framework Nanoreactors for High‐Efficiency Carbohydrates Separation and Labeling

Separation and labeling are the crucial steps for the carbohydrates identification and detection in the important field of biochemistry, biomedicine, glycomics, and glycobiology. Herein, for the first time, a boronic acid decorated defective metal–organic framework (B‐D‐MI‐100) nanoreactor is designed, which integrates fast separation and labeling of carbohydrates into one step. Without the sacrifice of internal room space, the incorporation of abundant functional boronic acid groups into the framework is achieved through metal–ligand–fragment coassembly strategy. And the novel solid phase orientation labeling approach performed within elaborate Cr based B‐D‐MIL‐100 nanoreactor is facile to avoid the conformation transition of carbohydrates occurred in classical liquid‐phase labeling. As a result, the novel approach presents several merits, including high separation efficiency (almost all of the incorporated boronic acid groups are available), much fast labeling reaction speed (labeling reaction time is decreased from 7 h to 3 min), high purity of the product, and three orders of magnitude lower applicable carbohydrate concentration for labeling. Thus, this new approach advances the idea to efficiently detect and identify trace carbohydrates in important fields such as glycomics and glycobiology.     

Visible‐Light Excited Luminescent Thermometer Based on Single Lanthanide Organic Frameworks

Isostructural lanthanide organic frameworks (Me₂NH₂)₃[Ln₃(FDC)₄(NO₃)₄]·4H₂O (Ln = Eu ( 1 ), Gd ( 2 ), Tb ( 3 ), H₂FDC = 9‐fluorenone‐2,7‐dicarboxylic acid), synthesized under solvothermal conditions, feature a Ln‐O‐C rod‐packing 3D framework. Time‐resolved luminescence studies show that in 1 the energy difference between the H₂FDC triplet excited state (17794 cm^?1) and the ⁵D₀ Eu³⁺ level (17241 cm^?1) is small enough to allow a strong thermally activated ion‐to‐ligand back energy transfer. Whereas the emission of the ligand is essentially constant the ⁵D₀→⁷F₂ intensity is quenched when the temperature increases from 12 to 320 K, rendering 1 the first single‐lanthanide organic framework ratiometric luminescent thermometer based on ion‐to‐ligand back energy transfer. More importantly, this material is also the first example of a metal organic framework thermometer operative over a wide temperature range including the physiological (12‐320 K), upon excitation with visible light (450 nm).     

Metal–Organic Framework Assisted and Tumor Microenvironment Modulated Synergistic Image‐Guided Photo‐Chemo Therapy

The complex tumor microenvironment (TME) and nonspecific drug targeting limit the clinical efficacy of photodynamic therapy in combination with chemotherapy. Herein, a metal–organic framework (MOF) assisted strategy is reported that modulates TME by reducing tumor hypoxia and intracellular glutathione (GSH) and offers targeted delivery and controlled release of the trapped chemodrug. Platinum(IV)‐diazido complex (Pt(IV)) is loaded inside a Cu(II) carboxylate‐based MOF, MOF‐199, and an aggregation‐induced‐emission photosensitizer, TBD, is conjugated to polyethylene glycol for encapsulating Pt(IV)‐loaded MOF‐199. Once the fabricated TBD‐Pt(IV)@MOF‐199 nanoparticles are internalized by cancer cells, MOF‐199 consumes intracellular GSH and decomposes to fragments to release Pt(IV). Upon light irradiation, the released Pt(IV) generates O₂ that relieves hypoxia and produces Pt(II)‐based chemodrug inside cancer cells. Concomitantly, efficient reactive oxygen species generation and bright emission are afforded by TBD, resulting in synergistic image‐guided photo‐chemo therapy with enhanced efficacies and mitigated side effects.     

A High‐Performance Sodium‐Ion Hybrid Capacitor Constructed by Metal–Organic Framework–Derived Anode and Cathode Materials

Sodium‐ion hybrid capacitors (SIHCs) can potentially combine the virtues of high‐energy density of batteries and high‐power output as well as long cycle life of capacitors in one device. The key point of constructing a high‐performance SIHC is to couple appropriate anode and cathode materials, which can well match in capacity and kinetics behavior simultaneously. In this work, a novel SIHC, coupling a titanium dioxide/carbon nanocomposite (TiO₂/C) anode with a 3D nanoporous carbon cathode, which are both prepared from metal–organic frameworks (MOFs, MIL‐125 (Ti) and ZIF‐8, respectively), is designed and fabricated. The robust architecture and extrinsic pseudocapacitance of TiO₂/C nanocomposite contribute to the excellent cyclic stability and rate capability in half‐cell. Hierarchical 3D nanoporous carbon displays superior capacity and rate performance. Benefiting from the merits of structures and performances of anode and cathode materials, the as‐built SIHC achieves a high energy density of 142.7 W h kg^?1 and a high power output of 25 kW kg^?1 within 1–4 V, as well as an outstanding life span of 10 000 cycles with over 90% of the capacity retention. The results make it competitive in high energy and power–required electricity storage applications.     

Massive Anisotropic Thermal Expansion and Thermo‐Responsive Breathing in Metal–Organic Frameworks Modulated by Linker Functionalization

Functionalized metal–organic frameworks (fu‐MOFs) of general formula [Zn₂(fu‐L)₂dabco]_n show unprecedentedly large uniaxial positive and negative thermal expansion (fu‐L = alkoxy functionalized 1,4‐benzenedicarboxylate, dabco = 1,4‐diazabicyclo[2.2.2]octane). The magnitude of the volumetric thermal expansion is more comparable to property of liquid water rather than any crystalline solid‐state material. The alkoxy side chains of fu‐L are connected to the framework skeleton but nevertheless exhibit large conformational flexibility. Thermally induced motion of these side chains induces extremely large anisotropic framework expansion and eventually triggers reversible solid state phase transitions to drastically expanded structures. The thermo‐responsive properties of these hybrid solid–liquid materials are precisely controlled by the choice and combination of fu‐Ls and depend on functional moieties and chain lengths. In principle, this combinatorial approach allows for a targeted design of extreme thermo‐mechanical properties of MOFs addressing the regime between crystalline solid matter and the liquid state.     

Atomic‐Scale CoOx Species in Metal–Organic Frameworks for Oxygen Evolution Reaction

The activity of electrocatalysts strongly depends on the number of active sites, which can be increased by downsizing electrocatalysts. Single‐atom catalysts have attracted special attention due to atomic‐scale active sites. However, it is a huge challenge to obtain atomic‐scale CoO_x catalysts. The Co‐based metal–organic frameworks (MOFs) own atomically dispersed Co ions, which motivates to design a possible pathway to partially on‐site transform these Co ions to active atomic‐scale CoO_x species, while reserving the highly porous features of MOFs. In this work, for the first time, the targeted on‐site formation of atomic‐scale CoO_x species is realized in ZIF‐67 by O₂ plasma. The abundant pores in ZIF‐67 provide channels for O₂ plasma to activate the Co ions in MOFs to on‐site produce atomic‐scale CoO_x species, which act as the active sites to catalyze the oxygen evolution reaction with an even better activity than RuO₂.     

Ultrasmall Au Nanoparticles Embedded in 2D Mixed‐Ligand Metal–Organic Framework Nanosheets Exhibiting Highly Efficient and Size‐Selective Catalysis

Metal–organic frameworks (MOFs) hold great promise as porous matrixes for the incorporation of Au nanoparticles (NPs) because of their rationally designed framework structures. Unfortunately, the as‐synthesized bulk MOFs usually vary in the range of micrometer or sub‐micrometer size, rendering extremely longer molecular diffusion distance of chemical species. 2D MOF nanosheets with extended lateral dimensions and nanometer thickness are expected to implement fast kinetics and effectively lower mass‐transfer barriers during embedding Au NPs process and sequential catalytic reactions. In this study, a novel 2D nanosheet of mixed‐ligand Ni(II) MOF (referred to NMOF‐Ni ) is successfully fabricated. With the merits of well‐defined micropores and functional oxygen‐decorated inner walls, the incorporation of quite monodisperse ultrasmall Au nanoparticles of around 1 nm into NMOF‐Ni has been achieved for the first time. The resulting nanocomposites exhibit remarkable catalytic performance and good size selectivity toward aqueous reduction reactions of nitrophenol, taking advantage of ultrasmall Au and 2D nanosheet nature, as well as the intact microporosity of host matrix. The present encouraging findings might shed light on new ways to develop high‐performance heterogeneous catalysts by using of 2D MOF nanosheets with functional cavities as hosts for homogeneous distribution of ultrasmall Au NPs.     

Metal–Organic Framework Material Inhibits Biofilm Formation of Pseudomonas aeruginosa

An 85% reduction in the bacterial attachment of Pseudomonas aeruginosa is achieved using a water‐stable metal–organic framework (MOF) blended with chitosan. These materials demonstrate this reduction in bacterial adhesion in the first 6 h and maintain it over the full 24 h exposure period, a remarkable impediment of biofilm formation to achieve, given the strength of this bacteria strain. The films elicit the same inhibitory effect after a second round of experiments, suggesting reusability of the materials. Characterization of the films by powder X‐ray diffraction, attenuated total reflectance‐IR, and scanning electron microscopy supports retention of the MOF structure within the chitosan matrix. The extensive control experiments employed in this study isolate the observed biological effects to the synthesized films, and not to possible leachates from the films. This presents the first account of using a water‐stable MOF within a polymer as a means to achieve an antibacterial surface by demonstrating an 85% reduction in bacterial attachment of Pseudomonas aeruginosa.     

Bimetal–Organic Framework: One‐Step Homogenous Formation and its Derived Mesoporous Ternary Metal Oxide Nanorod for High‐Capacity,High‐Rate,and Long‐Cycle‐Life Lithium Storage

Metal–organic frameworks (MOFs) and relative structures with uniform micro/mesoporous structures have shown important applications in various fields. This paper reports the synthesis of unprecedented mesoporous Ni_xCo_3?xO₄ nanorods with tuned composition from the Co/Ni bimetallic MOF precursor. The Co/Ni‐MOFs are prepared by a one‐step facile microwave‐assisted solvothermal method rather than surface metallic cation exchange on the preformed one‐metal MOF template, therefore displaying very uniform distribution of two species and high structural integrity. The obtained mesoporous Ni_0.3Co_2.7O₄ nanorod delivers a larger‐than‐theoretical reversible capacity of 1410 mAh g^?1 after 200 repetitive cycles at a small current of 100 mA g^?1 with an excellent high‐rate capability for lithium‐ion batteries. Large reversible capacities of 812 and 656 mAh g^?1 can also be retained after 500 cycles at large currents of 2 and 5 A g^?1, respectively. These outstanding electrochemical performances of the ternary metal oxide have been mainly attributed to its interconnected nanoparticle‐integrated mesoporous nanorod structure and the synergistic effect of two active metal oxide components.