Metal–Organic Framework Derived Co3O4/TiO2/Si Heterostructured Nanorod Array Photoanodes for Efficient Photoelectrochemical Water Oxidation

A novel hierarchical structured photoanode based on metal–organic frameworks (MOFs)‐derived porous Co₃O₄‐modified TiO₂ nanorod array grown on Si (MOFs‐derived Co₃O₄/TiO₂/Si) is developed as photoanode for efficiently photoelectrochemical (PEC) water oxidation. The ternary Co₃O₄/TiO₂/Si heterojunction displays enhanced carrier separation performance and electron injection efficiency. In the ternary system, an abnormal type‐II heterojunction between TiO₂ and Si is introduced, because the conduction band and valence band position of Si are higher than those of TiO₂, the photogenerated electrons from TiO₂ will rapidly recombine with the photogenerated holes from Si, thus leading to an efficient separation of photogenerated electrons from Si/holes from TiO₂ at the TiO₂/Si interface, greatly improving the separation efficiency of photogenerated hole within TiO₂ and enhances the photogenerated electron injection efficiency in Si. While the MOFs‐derived Co₃O₄ obviously improves the optical‐response performance and surface water oxidation kinetics due to the large specific surface area and porous channel structure. Compared with MOFs‐derived Co₃O₄/TiO₂/FTO photoanode, the synergistic function in the MOFs‐derived Co₃O₄/TiO₂/Si NR photoanode brings greatly enhanced photoconversion efficiency of 0.54% (1.04 V vs reversible hydrogen electrode) and photocurrent density of 2.71 mA cm^?2 in alkaline electrolyte. This work provides promising methods for constructing high‐performance PEC water splitting photoanode based on MOFs‐derived materials.     

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.     

Hybrid 2D Dual‐Metal–Organic Frameworks for Enhanced Water Oxidation Catalysis

Metal–organic frameworks (MOFs) and MOF‐derived nanostructures are recently emerging as promising catalysts for electrocatalysis applications. Herein, 2D MOFs nanosheets decorated with Fe‐MOF nanoparticles are synthesized and evaluated as the catalysts for water oxidation catalysis in alkaline medium. A dramatic enhancement of the catalytic activity is demonstrated by introduction of electrochemically inert Fe‐MOF nanoparticles onto active 2D MOFs nanosheets. In the case of active Ni‐MOF nanosheets (Ni‐MOF@Fe‐MOF), the overpotential is 265 mV to reach a current density of 10 mA cm^?2 in 1 m KOH, which is lowered by ≈100 mV after hybridization due to the 2D nanosheet morphology and the synergistic effect between Ni active centers and Fe species. Similar performance improvement is also successfully demonstrated in the active NiCo‐MOF nanosheets. More importantly, the real catalytic active species in the hybrid Ni‐MOF@Fe‐MOF catalyst are unraveled. It is found that, NiO nanograins (≈5 nm) are formed in situ during oxygen evolution reaction (OER) process and act as OER active centers as well as building blocks of the porous nanosheet catalysts. These findings provide new insights into understanding MOF‐based catalysts for water oxidation catalysis, and also shed light on designing highly efficient MOF‐derived nanostructures for electrocatalysis.     

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.     

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.     

Metal–Organic Framework‐Derived Graphitic Nanoribbons Anchored on Graphene for Electroionic Artificial Muscles

To achieve large bending displacement and fast response time under ultralow input voltages, as well as improved durability, advanced high‐performance ionic actuators still face crucial design challenges that must be resolved. Here, hierarchically porous and unzipped graphitic nanoribbons anchored on graphene as an efficient electrode material for high‐performance electroionic artificial muscles are reported. Using controlled solvothermal and pyrolysis methods, nanoarchitectured carbon is derived from a self‐templated potassium‐based metal–organic frameworks–graphene hybrid. The newly designed ionic actuator demonstrates excellent actuation performance, including large bending displacement (17.4 mm) and a strain difference of 0.51% at 0.5 V AC input, very fast response time (700 ms) at 0.5 V DC input, wide frequency response (0.1–15 Hz), and excellent cycling stability (92%) after 25 000 cycles without any delamination of electrodes under continuous electrical operation. The breakthrough in actuation performance mainly stems from the unzipping of hollow nanorods to hierarchical porous graphitic nanoribbons anchored on graphene with the enlarged surface area, large pore volume, stronger mechanical integrity, and emerging charge storage and transport ability. Further, the electroionic actuator shows promise when applied in the demonstration of a biomimicking Venus flytrap.     

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.     

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.     

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.     

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.     

Amorphous Cobalt–Iron Hydroxide Nanosheet Electrocatalyst for Efficient Electrochemical and Photo‐Electrochemical Oxygen Evolution

Finding efficient electrocatalysts for oxygen evolution reaction (OER) that can be effectively integrated with semiconductors is significantly challenging for solar‐driven photo‐electrochemical (PEC) water splitting. Herein, amorphous cobalt–iron hydroxide (CoFe? H) nanosheets are synthesized by facile electrodeposition as an efficient catalyst for both electrochemical and PEC water oxidation. As a result of the high electrochemically active surface area and the amorphous nature, the optimized amorphous CoFe? H nanosheets exhibit superior OER catalytic activity in alkaline environment with a small overpotential (280 mV) to achieve significant oxygen evolution (j = 10 mA cm^?2) and a low Tafel slope (28 mV dec^?1). Furthermore, CoFe? H nanosheets are simply integrated with BiVO₄ semiconductor to construct CoFe? H/BiVO₄ photoanodes that exhibit a significantly enhanced photocurrent density of 2.48 mA cm^?2 (at 1.23 V vs reversible hydrogen electrode (RHE)) and a much lower onset potential of 0.23 V (vs RHE) for PEC‐OER. Careful electrochemical and optical studies reveal that the improved OER kinetics and high‐quality interface at the CoFe? H/BiVO₄ junction, as well as the excellent optical transparency of CoFe? H nanosheets, contribute to the high PEC performance. This study establishes amorphous CoFe? H nanosheets as a highly competitive candidate for electrochemical and PEC water oxidation and provides general guidelines for designing efficient PEC systems.     

Rapid Detection of the Biomarkers for Carcinoid Tumors by a Water Stable Luminescent Lanthanide Metal–Organic Framework Sensor

Serotonin (5‐hydroxytryptamine, HT), a neurotransmitter, and its main metabolite 5‐hydroxyindole‐3‐acetic acid (HIAA) are biomarkers for carcinoid tumors. They can be quantitatively detected by a new luminescent sensor based on a water stable lanthanide metal–organic framework (Ln‐MOF). This Ln‐MOF features a (3,4)‐connected topology containing 1D channels occupied by lattice water molecules. Luminescent studies reveal that high luminescence quenching efficiency occurs upon the addition of HT and HIAA. The Ln‐MOF also displays excellent sensitivity with fast response within 1 min, good reusability, and detection limits as low as 0.66 and 0.54 × 10^?6m for HT and HIAA, respectively. In addition, the sensing function exhibits excellent selectivity even in the presence of other neurotransmitters and the main coexisting species in blood plasma and urine.     

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.     

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.     

Lanthanide–Organic Framework Nanothermometers Prepared by Spray‐Drying

Accurate, noninvasive, and self‐referenced temperature measurements at the submicrometer scale are of great interest, prompted by the ever‐growing demands in the fields of nanotechnology and nanomedicine. The thermal dependence of the phosphor's luminescence provides high detection sensitivity and spatial resolution with short acquisition times in, e.g., biological fluids, strong electromagnetic fields, and fast‐moving objects. Here, it is shown that nanoparticles of [(Tb_0.914Eu_0.086)₂(PDA)₃(H₂O)]·2H₂O (PDA = 1,4‐phenylenediacetic acid), the first lanthanide–organic framework prepared by the spray‐drying method, are excellent nanothermometers operating in the solid state in the 10–325 K range (quantum yield of 0.25 at 370 nm, at room temperature). Intriguingly, this system is the most sensitive cryogenic nanothermometer reported so far, combining high sensitivity (up to 5.96 ± 0.04% K^?1 at 25 K), reproducibility (in excess of 99%), and low‐temperature uncertainty (0.02 K at 25 K).     

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.