From salt water to bioceramics: Mimic nature through pressure-controlled hydration and crystallization.

Modern synthetic technology generally invokes high temperatures to control the hydration level of ceramics, but even the state-of-the-art technology can still only control the overall hydration content. Magically, natural organisms can produce bioceramics with tailorable hydration profiles and crystallization traits solely from amorphous precursors under physiological conditions. To mimic the biomineralization tactic, here, we report pressure-controlled hydration and crystallization in fabricated ceramics, solely from the amorphous precursors of purely inorganic gels (PIGs) synthesized from biocompatible aqueous solutions with most common ions in organisms (Ca2+, Mg2+, CO32-, and PO43-). Transparent ceramic tablets are directly produced by compressing the PIGs under mild pressure, while the pressure regulates the hydration characteristics and the subsequent crystallization behaviors of the synthesized ceramics. Among the various hydration species, the moderately bound and ordered water appears to be a key in regulating the crystallization rate. This nature-inspired study offers deeper insights into the magic behind biomineralization.

Insight into the Gas-Induced Phase Transformations in a 2D Switching Coordination Network via Coincident Gas Sorption and In Situ PXRD.

Switching coordination networks (CNs) that reversibly transform between narrow or closed pore (cp) and large pore (lp) phases, though fewer than their rigid counterparts, offer opportunities for sorption-related applications. However, their structural transformations and switching mechanisms remain underexplored at the molecular level. In this study, we conducted a systematic investigation into a 2D switching CN, [Ni(bpy)2(NCS)2]n, sql-1-Ni-NCS (1 = bpy = 4,4'-bipyridine), using coincident gas sorption and in situ powder X-ray diffraction (PXRD) under low-temperature conditions. Gas adsorption measurements revealed that C2H4 (169 K) and C2H6 (185 K) exhibited single-step type F-IVs sorption isotherms with sorption uptakes of around 180-185 cm3 g-1, equivalent to four sorbate molecules per formula unit. Furthermore, parallel in situ PXRD experiments provided insight into sorbate-dependent phase switching during the sorption process. Specifically, CO2 sorption induced single-step phase switching (path I) solely between cp and lp phases consistent with the observed single-step type F-IVs sorption isotherm. By contrast, intermediate pore (ip) phases emerged during C2H4 and C2H6 desorption as well as C3H6 adsorption, although they remained undetectable in the sorption isotherms. To our knowledge, such a cp-lp-ip-cp transformation (path II) induced by C2H4/6 and accompanied by single-step type F-IVs sorption isotherms represents a novel type of phase transition mechanism in switching CNs. By virtue of Rietveld refinements and molecular simulations, we elucidated that the phase transformations are governed by cooperative local and global structural changes involving NCS- ligand reorientation, bpy ligand twist and rotation, cavity edge (Ni-bpy-Ni) deformation, and interlayer expansion and sliding.

Removing Perfluoro Pollutants PFOA and PFOS by Two-Pronged Design of a Ni8-Pyrazolate Porous Framework.

Inspired by the practical need to remove persistent perfluoro pollutants from the environment, we leverage cutting-edge crystal engineering approaches. For this, we set our eyes on a recent porous coordination framework system based on the Ni8-oxo cluster and pyrazolate linkers as it is known for its stability to bases and other harsh environmental conditions. Our designer linker molecule here features (1) pyrazole donors masked by t-butyloxycarbonyl and (2) ethynyl side units protected by triisopropylsilyl groups. The former solvothermally demasks to assemble the Ni8-pyrazolate framework, in which the triisopropylsilyl groups can be post-synthetically cleaved by guest fluoride ions to unveil the terminal alkyne group (-CCH). The ethynyl groups of the framework solid offer versatile reactions for functionalization, as with perfluorophenyl azide (via a click reaction) to afford the two prongs of the 1,2,3-triazole base unit and the perfluoro unit. Together, these two functions make for an effective adsorbent for the topical acid pollutants of perfluorooctanoic acid and perfluorooctanesulfonic acid, with a high apparent rate constant (kobs) of 0.99 g mg-1 h-1 and large maximum uptake capacity (qmax) of 268.5 mg g-1 for perfluorooctanoic acid and kobs of 0.77 g mg-1 h-1 and qmax of 142.1 mg g-1 for perfluorooctanesulfonic acid.

Minimalist Design for Solar Energy Conversion: Revamping the π-Grid of an Organic Framework into Open-Shell Superabsorbers.

We apply a versatile reaction to a versatile solid: the former involves the electron-deficient alkene tetracyanoethylene (TCNE) as the guest reactant; the latter consists of stacked 2D honeycomb covalent networks based on the electron-rich ß-ketoenamine hinges that also activate the conjugated, connecting alkyne units. The TCNE/alkyne reaction is a [2 + 2] cycloaddition-retroelectrocyclization (CA-RE) that forms strong push-pull units directly into the backbone of the framework-i.e., using only the minimalist "bare-bones" scaffold, without the need for additional side groups of alkynes or other functions. The ability of the stacked alkyne units (i.e., as part of the honeycomb mass) to undergo such extensive rearrangement highlights the structural flexibility of these covalent organic framework (COF) hosts. The COF solids remain porous, crystalline, and air-/water-stable after the CA-RE modification, while the resulting push-pull units feature distinct open-shell/free-radical character, are strongly light-absorbing, and shift the absorption ends from 590 nm to around 1900 nm (band gaps from 2.17-2.23 to 0.87-0.95 eV), so as to better capture sunlight (especially the infrared region which takes up 52% of the solar energy). As a result, the modified COF materials achieve the highest photothermal conversion performances, holding promise in thermoelectric power generation and solar steam generation (e.g., with solar-vapor conversion efficiencies >96%).

Charge Separation in Metal-Organic Framework Enables Heterogeneous Thiol Catalysis.

Photoinduced metal-organic framework (MOF) enabled heterogeneous thiol catalysis has been achieved for the first time. MOF Zr-TPDCS-1, consisting of Zr6 -clusters and TPDCS linkers (TPDCS=3,3'',5,5''-tetramercapto[1,1':4',1''-terphenyl]-4,4''-dicarboxylate), effectively catalyzed the borylation, silylation, phosphorylation, and thiolation of organic molecules. Upon irradiation, the fast electron transfer from TPDCS to Zr6 -cluster is believed to facilitate the formation of the thiyl radical, a hydrogen atom transfer catalyst, which competently abstracts the hydrogen from borane, silane, phosphine, or thiol for generating the corresponding element radical to engender the chemical transformations. The elaborate control experiments evidenced the generation of thiyl radicals in MOF and illustrated a radical reaction pathway. The gram-scale reaction worked well, and the product was conveniently separated via centrifugation and vacuum with a turnover number (TON) of ≈3880, highlighting the practical application potential of heterogeneous thiyl-radical catalysis.

Multi-Label Hashing for Dependency Relations among Multiple Objectives.

Learning hash functions have been widely applied for large-scale image retrieval. Existing methods usually use CNNs to process an entire image at once, which is efficient for single-label images but not for multi-label images. First, these methods cannot fully exploit independent features of different objects in one image, resulting in some small object features with important information being ignored. Second, the methods cannot capture different semantic information from dependency relations among objects. Third, the existing methods ignore the impacts of imbalance between hard and easy training pairs, resulting in suboptimal hash codes. To address these issues, we propose a novel deep hashing method, termed multi-label hashing for dependency relations among multiple objectives (DRMH). We first utilize an object detection network to extract object feature representations to avoid ignoring small object features and then fuse object visual features with position features and further capture dependency relations among objects using a self-attention mechanism. In addition, we design a weighted pairwise hash loss to solve the imbalance problem between hard and easy training pairs. Extensive experiments are conducted on multi-label datasets and zero-shot datasets, and the proposed DRMH outperforms many state-of-the-art hashing methods with respect to different evaluation metrics.

Molecular Engineering of Metal-Organic Frameworks as Efficient Electrochemical Catalysts for Water Oxidation.

Metal-organic framework (MOF) solids with their variable functionalities are relevant for energy conversion technologies. However, the development of electroactive and stable MOFs for electrocatalysis still faces challenges. Here, a molecularly engineered MOF system featuring a 2D coordination network based on mercaptan-metal links (e.g., nickel, as for Ni(DMBD)-MOF) is designed. The crystal structure is solved from microcrystals by a continuous-rotation electron diffraction (cRED) technique. Computational results indicate a metallic electronic structure of Ni(DMBD)-MOF due to the Ni-S coordination, highlighting the effective design of the thiol ligand for enhancing electroconductivity. Additionally, both experimental and theoretical studies indicate that (DMBD)-MOF offers advantages in the electrocatalytic oxygen evolution reaction (OER) over non-thiol (e.g., 1,4-benzene dicarboxylic acid) analog (BDC)-MOF, because it poses fewer energy barriers during the rate-limiting *O intermediate formation step. Iron-substituted NiFe(DMBD)-MOF achieves a current density of 100 mA cm-2 at a small overpotential of 280 mV, indicating a new MOF platform for efficient OER catalysis.

Renal-clearable porous hollow copper iron oxide nanoparticles for trimodal chemodynamic-photothermal-chemo anti-tumor therapy.

Multifunctional nanoplatforms with the synergistic effects of multiple therapeutic modalities have become a research focus due to their superior anti-tumor properties over single therapeutic modalities. Herein, we developed around 14 nm porous hollow copper iron oxide nanoparticles (PHCuFeNPs) with pore sizes of around 2-3 nm as a cisplatin carrier and photothermal therapeutic agent. The PHCuFeNPs were synthesized via a galvanic reaction between Cu2S nanoparticles and iron pentacarbonyl (Fe(CO)5) followed by etching in the organic phase to make the pores. They were stable under normal physiological conditions, but the pores were etched in a weak acidic tumor microenvironment, resulting in the controlled release of Cu and Fe ions for enhanced chemodynamic therapy and accelerated cisplatin release for chemotherapy. Under 980 nm laser irradiation, the PHCuFeNPs could effectively heat up to further promote the release process for synergistic therapy. Besides, they were proved to mediate immunogenic cell death to activate the immune system for potential immunotherapy. Together with their ability to degrade into fragments for fast renal metabolism, we believe that these PHCuFeNPs could provide a biocompatible and efficient multi-antitumor therapeutic approach.

Effects of Nonthermal Radiofrequency Stimulation on Neuronal Activity and Neural Circuit in Mice.

Whether the nonthermal effects of radiofrequency radiation (RFR) exist and how nonthermal RFR acts on the nervous system are unknown. An animal model of spatial memory impairment is established by exposing mice to 2856-MHz RFR in the range of thermal noise (≤1 °C). Glutamate release in the dorsal hippocampus (dHPC) CA1 region is not significantly changed after radiofrequency exposure, whereas dopamine release is reduced. Importantly, RFR enhances glutamatergic CA1 pyramidal neuron calcium activity by nonthermal mechanisms, which recover to the basal level with RFR termination. Furthermore, suppressed dHPC dopamine release induced by radiofrequency exposure is due to decreased density of dopaminergic projections from the locus coeruleus to dHPC, and artificial activation of dopamine axon terminals or D1 receptors in dHPC CA1 improve memory damage in mice exposed to RFR. These findings indicate that nonthermal radiofrequency stimulation modulates ongoing neuronal activity and affects nervous system function at the neural circuit level.

Organic radicals stabilization above 300 °C in Eu-based coordination polymers for solar steam generation.

Organic radicals feature unpaired electrons, and these compounds may have applications in biomedical technology and as materials for solar energy conversion. However, unpaired electrons tend to pair up (to form chemical bonds), making radicals unstable and hampering their applications. Here we report an organic radical system that is stable even at 350 °C, surpassing the upper temperature limit (200 °C) observed for other organic radicals. The system reported herein features a sulfur-rich organic linker that facilitates the formation of the radical centers; on the solid-state level, the molecules are crystallized with Eu(III) ions to form a 3D framework featuring stacks of linker molecules. The stacking is, however, somewhat loose and allows the molecules to wiggle and transform into sulfur-stabilized radicals at higher temperatures. In addition, the resulting solid framework remains crystalline, and it is stable to water and air. Moreover, it is black and features strong broad absorption in the visible and near IR region, thereby enhancing both photothermal conversion and solar-driven water evaporation.

Superprotonic conduction of intrinsically zwitterionic microporous polymers based on easy-to-make squaraine, croconaine and rhodizaine dyes.

Porous organic polymers (POPs) have been prepared via a novel metal free polycondensation between a tritopic indole-based monomer and squaric, croconic and rhodizonic acids. Each of the three POPs exhibited high BET surface areas (331-667 m2 g-1) and zwitterionic structures. Impedance measurements revealed that the intrinsic POPs were relatively weak proton conductors, with a positive correlation between the density of oxo-groups and the proton conduction. Doping the materials with LiCl vastly improved the proton conductivity up to a value of 0.54 S cm-1 at 90 °C and 90% relative humidity.

High-Power Electromagnetic Pulse Exposure of Healthy Mice: Assessment of Effects on Mice Cognitions, Neuronal Activities, and Hippocampal Structures.

Electromagnetic pulse (EMP) is a high-energy pulse with an extremely rapid rise time and a broad bandwidth. The brain is a target organ sensitive to electromagnetic radiation (EMR), the biological effects and related mechanisms of EMPs on the brain remain unclear. The objectives of the study were to assess the effects of EMP exposure on mouse cognitions, and the neuronal calcium activities in vivo under different cases of real-time exposure and post exposure. EMP-treated animal model was established by exposing male adult C57BL/6N mice to 300 kV/m EMPs. First, the effects of EMPs on the cognitions, including the spatial learning and memory, avoidance learning and memory, novelty-seeking behavior, and anxiety, were assessed by multiple behavioral experiments. Then, the changes in the neuronal activities of the hippocampal CA1 area in vivo were detected by fiber photometry in both cases of during real-time EMP radiation and post-exposure. Finally, the structures of neurons in hippocampi were observed by optical microscope and transmission electron microscope. We found that EMPs under this condition caused a decline in the spatial learning and memory ability in mice, but no effects on the avoidance learning and memory, novelty-seeking behavior, and anxiety. The neuron activities of hippocampal CA1 were disturbed by EMP exposure, which were inhibited during EMP exposure, but activated immediately after exposure end. Additionally, the CA1 neuron activities, when mice entered the central area in an Open field (OF) test or explored the novelty in a Novel object exploration (NOE) test, were inhibited on day 1 and day 7 after radiation. Besides, damaged structures in hippocampal neurons were observed after EMP radiation. In conclusion, EMP radiation impaired the spatial learning and memory ability and disturbed the neuronal activities in hippocampal CA1 in mice.

Carbazole-Equipped Metal-Organic Framework for Stability, Photocatalysis, and Fluorescence Detection.

The useful yet underutilized backfolded design is invoked here for functionalizing porous solids with the versatile carbazole function. Specifically, we attach carbazole groups as backfolded side arms onto the backbone of a linear dicarboxyl linker molecule. The bulky carbazole side arms point away from the carboxyl links and do not disrupt the Zr-carboxyl framework formation; namely, the resultant MOF solid ZrL1 features the same net as that of the unfunctionalized dicarboxyl linker, also known as the PCN-111 net or UiO-66 net. The ZrL1 structure features only half linker occupancy (about 6 out of the 12 linkers around the Zr6O8 cluster being missing) and partially collapses upon activation (acetone exchange and evacuation). Notably, the stability improves after heating in diphenyl oxide at 260 °C (POP-260 treatment; to form ZrL1-260), as indicated by the higher crystallinity and surface area of the activated ZrL1-260 sample. The ZrL1-260 samples achieve 72% yield in photocatalyzing reductive dehalogenation of phenacyl bromide; ZrL1 can detect nitro-aromatic compounds via fluorescence quenching, with selectivity and sensitivity toward 4-nitroaniline, featuring a limit of detection of 96 ppb.

Correction to Covalent Triazine Frameworks Embedded with Ir Complexes for Enhanced Photocatalytic Hydrogen Evolution.

[This corrects the article DOI: 10.1021/acsaem.2c00977.].

A facile approach for hierarchical architectures of an enzyme-metal-organic framework biocatalyst with high activity and stability.

Enzyme-incorporated composites with hierarchical porous structures can lead to improved performance of hybrid biocatalysts. Metal-organic frameworks (MOFs) have recently emerged as excellent biomineralizable materials for forming hybrid biocatalysts, offering superior performance for biocatalytic reactions. However, the small nanopores of MOFs significantly reduce the diffusion rates of small substrate molecules, hindering the contact between the inner active sites of an enzyme and the molecules, lowering the biocatalytic efficiency. Here, we used a solution-phase self-assembly method for preparing macroporous hierarchical porous architectures of a copper 5-(ethylthio)-1H-tetrazole [Cu(ett)] MOF, the distorted tetrahedral coordination geometry of which is favourable for producing macropores. Notably, the formation of [Cu(ett)] MOF hybrid biocatalysts is achieved via an in situ mineralization of enzymes, but without changes in the hierarchical porous structure. These properties lead to excellent catalytic activities as they decrease the inherent barriers to accelerate the diffusion rate of reactants. Moreover, the developed hierarchical porous MOFs demonstrated outstanding tolerance to inhospitable surroundings and favourable storage stability at room temperature.

Dense Dithiolene Units on Metal-Organic Frameworks for Mercury Removal and Superprotonic Conduction.

With 2-COOH and 4-SH donors all packed onto the benzene ring, tetrasulfanyl terephthalic acid (TST) is a simple yet fully equipped ligand to move the field of metal-coordination materials─it is now accomplished. The hard-soft carboxyl-thiol synergy is leveraged here in selectively bonding the carboxyl units to Zr(IV) ions to form the same cubic net of UiO-66 (this being based on the terephthalic linker)─with the free-standing dithiolene units equipping the grid of ZrTST. The 3D network of ZrTST averages about 7.6 connections [as in Zr6O4(OH)4(C8H4O4S4)3.8], with the other 4.4 sealed by acetate ions. The ZrTST solid is stable in boiling water (it is formed in water/acetic acid/ethane dithiol) and remains ordered even above 300 °C. The thiol-enabled ZrTST (powder) takes up mercury from water with a high distribution coefficient Kd (e.g., 1.2 × 106 mL·g-1); it also shows proton conductivity (1.9 × 10-3 S·cm-1 at 90 °C and 90% relative humidity), which, most notably, increases to a highest value of 3.7 × 10-1 S·cm-1 after oxidizing the -SH into the -SO3H groups.

A Ferrocene Metal-Organic Framework Solid for Fe-Loaded Carbon Matrices and Nanotubes: High-Yield Synthesis and Oxygen Reduction Electrocatalysis.

Using a carbon-rich designer metal-organic framework (MOF), we open a high-yield synthetic strategy for iron-nitrogen-doped carbon (Fe-N-C) nanotube materials that emulate the electrocatalysis performance of commercial Pt/C. The Zr(IV)-based MOF solid boasts multiple key functions: (1) a dense array of alkyne units over the backbone and the side arms, which are primed for extensive graphitization; (2) the open, branched structure helps maintain porosity for absorbing nitrogen dopants; and (3) ferrocene units on the side arms as atomically dispersed precursor catalyst for targeting micropores and for effective iron encapsulation in the carbonized product. As a result, upon pyrolysis, over 89% of the carbon component in the MOF scaffold is successfully converted into carbonized products, thereby contrasting the easily volatilized carbon of most MOFs. Moreover, over 97% of the iron ends up being encased as acid-resistant Fe/Fe3C nanoparticles in carbon nanotubes/carbon matrices.

Invisible Silver Guests Boost Order in a Framework That Cyclizes and Deposits Ag3Sb Nanodots.

The infusion of metal guests into (i.e., metalating) the porous medium of metal-organic frameworks (MOFs) is a topical approach to wide-ranging functionalization purposes. We report the notable interactions of AgSbF6 guests with the designer MOF host ZrL1 [Zr6O4(OH)7(L1)4.5(H2O)4]. (1) The heavy-atom guests of AgSbF6 induce order in the MOF host to allow the movable alkyne side arm to be fully located by X-ray diffraction, but they themselves curiously remain highly disordered and absent in the strucutral model. The enhanced order of the framework can be generally ascribed to interaction of the silver guests with the host alkyne and thioether functions, while the invisible heavy-atom guest represents a new phenomenon in the metalation of open framework materials. (2) The AgSbF6 guests also participate in the thermocyclization of the vicinal alkyne units of the L1 linker (at 450 °C) and form the rare nanoparticle of Ag3Sb supported on the concomitantly formed nanographene network. The resulted composite exhibits high electrical conductivity (1.0 S/cm) as well as useful, mitigated catalytic activity for selectively converting nitroarenes into the industrially important azo compounds, i.e., without overshooting to form the amine side products. The heterogeneous/cyclable catalysis entails only the cheap reducing reagents of NaBH4, ethanol, and water, with yields being generally close to 90%.

High-Purity and Saturated Deep-Blue Luminescence from trans-NHC Platinum(II) Butadiyne Complexes: Properties and Organic Light Emitting Diode Application.

Two new platinum(II) compounds with trans-(NHC)2Pt(C≡C-C≡C-R)2 (where NHC = N-heterocyclic carbene and R = phenyl or trimethylsilyl) architecture exhibit sharp blue-green or saturated deep-blue phosphorescence with high color purity. The photoluminescence of both compounds is dominated by an intense 0-0 band with distinct but weaker vibronic progressions in both tetrahydrofuran (THF) and poly(methyl methacrylate) (PMMA) matrix. The full width at half-maximum (fwhm) of the photoluminescence of trans-(NHC)2Pt(C≡C-C≡C-trimethylsilyl)2 are 10 nm at room temperature and 4 nm at 77 K, while the trans-(NHC)2Pt(C≡C-C≡C-phenyl)2 shows a fwhm of 14 nm at room temperature and 8 nm at 77 K. The Commission International de L'Eclairage (CIE) coordinates of trans-(NHC)2Pt(C≡C-C≡C-phenyl)2 are (0.222, 0.429) in PMMA, and trans-(NHC)2Pt(C≡C-C≡C-trimethylsilyl)2 has a deep-blue CIE of (0.163, 0.077) in PMMA. When doped into PMMA, the phosphorescence quantum yield of the complex with trimethylsilyl-butadiyne ligand increases dramatically to 57% from 0.25% in THF, while the complex with phenyl-butadiyne ligand has similar quantum yields in PMMA (32%) and THF (37%). Organic light-emitting diodes (OLEDs) employing these two complexes as the emitters were successfully fabricated with electroluminescence that closely matches the corresponding photoluminescence. The OLEDs based on trans-(NHC)2Pt(C≡C-C≡C-trimethylsilyl)2 display highly pure deep-blue electroluminescence (fwhm = 12 nm) with CIE coordinates of (0.172, 0.086), approaching the most stringent National Television System Committee (NTSC) coordinates for "pure" blue of (0.14, 0.08).

Conjugated crosslinks boost the conductivity and stability of a single crystalline metal-organic framework.

A linker molecule with four pendant thiophene functions was crystallized with Zr(iv) ions to form a semiconductive porous coordination solid (1.1 × 10-5 S cm-1). Oxidative treatment with FeCl3 guests then coupled the thiophene units to form conjugated bridges as covalent crosslinks. The resulting hybrid of a metal-organic framework and conjugated polymer featured robust crystalline order that withstood long-term air exposure and broad pH (from 0 to 12) conditions. Moreover, the homocoupled thiophene units, conjugated through sulfide links (-S-) with the linker backbone, afforded higher electronic conductivity (e.g., >2.2 × 10-3 S cm-1), which is characteristic of conductive polymer prototypes of polythiophene and polyphenylene sulfide. The crosslinked solid also exhibited proton conductivity that could be increased broadly upon H2SO4 treatment (e.g., from 5.0 × 10-7 to 1.6 × 10-3 S cm-1).