Structural Variants and Ultralow Detection Ability for Tryptamine in Two Polymorphs of a Zincophosphite Framework.

Two organic-inorganic hybrid zinc phosphites incorporating 1,2,4,5-tetrakis(imidazol-1-ylmethyl)benzene (TIMB) molecules were synthesized under hydro(solvo)thermal methods and structurally characterized by single-crystal X-ray diffraction (SCXD). Interestingly, the solvent ratio of water to dimethylformamide induced the formation of a new compound of Zn2(TIMB)0.5(HPO3)2·3H2O (1) and our previously reported structure of Zn2(TIMB)0.5(HPO3)2·H2O (2). Additionally, their dehydrated crystals (1a and 2a) were prepared through heat treatment at 150 °C. SCXD and powder X-ray diffraction showed that all four compounds share the same framework formula of Zn2(TIMB)0.5(HPO3)2 but exhibit a huge difference in their inorganic components and final structures. In 1 and 1a, the inorganic units formed two-dimensional zincophosphite layers, while in 2 and 2a, they formed one-dimensional chains. The inorganic parts of 1 (1a) and 2 (2a) were bridged with TIMB linkers, resulting in 3D structures with rectangular and tubular windows, respectively. Furthermore, 1 was coated on the screen-printed carbon electron as a hybrid material, displaying excellent performance while having a linear relationship with an R2 value of 0.99 within the concentration range of 10-10 to 10-6 mol/L for detecting tryptamine (Try) molecules. Moreover, the results showed that 1 exhibits an ultralow limit of detection of 5.43 × 10-11 mol/L and high specificity toward Try over histamine, ascorbic acid, uric acid, and glucose. The synthesis, structural diversity, stability, and sensing ability are also discussed.

Microfluidic Biosensor Decorated with an Indium Phosphate Nanointerface for Attomolar Dopamine Detection.

Developing functional materials that directly integrate into miniaturized devices for sensing applications is essential for constructing the next-generation point-of-care system. Although crystalline structure materials such as metal organic frameworks are attractive materials exhibiting promising potential for biosensing, their integration into miniaturized devices is limited. Dopamine (DA) is a major neurotransmitter released by dopaminergic neurons and has huge implications in neurodegenerative diseases. Integrated microfluidic biosensors capable of sensitive monitoring of DA from mass-limited samples is thus of significant importance. In this study, we developed and systematically characterized a microfluidic biosensor functionalized with the hybrid material composed of indium phosphate and polyaniline nanointerfaces for DA detection. Under the flowing operation, this biosensor displays a linear dynamic sensing range going from 10-18 to 10-11 M and a limit of detection (LOD) value of 1.83 × 10-19 M. In addition to the high sensitivity, this microfluidic sensor showed good selectivity toward DA and high stability (>1000 cycles). Further, the reliability and practical utility of the microfluidic biosensor were demonstrated using the neuro-2A cells treated with the activator, promoter, and inhibiter. These promising results underscore the importance and potential of microfluidic biosensors integrated with hybrid materials as advanced biosensors systems.

Genuine Pores in a Stable Zinc Phosphite for High H2 Adsorption and CO2 Capture.

Invited for the cover of this issue are Chih-Min Wang and co-workers at Academia Sinica of Taiwan and National Taiwan Ocean University. The image depicts an unusual organic-inorganic hybrid zinc phosphite with interesting structural features and gas adsorption properties. Read the full text of the article at 10.1002/chem.202200732.

Uncommon 3D Twofold Interpenetrated Zinc Phosphate Consisting of Inorganic Chains and Mixed Ligands for Highly Efficient Dye Removal Ability Using Its Nanosized Particles.

The flexible blocks are the primary building units for constructing crystalline solids with interpenetrating structures. Herein, we reported a novel class of crystalline material with such structural features, which was made of two tetradentate ligands and one-dimensional (1D) rigid chains of zinc phosphate. This is also the first example of transition metal phosphate incorporating a squarate linker. Furthermore, efficient dye removal ability has been presented.

Hetero-interpenetrating porous coordination polymers.

Interpenetrating porous coordination polymers (IPCPs) consist of two or more networks that are mechanically interlocked to form a coherent structure. The framework topology and the chemical composition are the two important criteria of interpenetrating networks to distinguish homo-IPCPs from hetero-IPCPs. Compared to rich homo-IPCPs, hetero-IPCPs remain rare and are formed rather unexpectedly. This Frontier article highlights hetero-IPCPs in accordance with the difference and/or identity of individual networks in terms of the framework topology and the chemical composition.

Genuine Pores in a Stable Zinc Phosphite for High H2 Adsorption and CO2 Capture.

An uncommon example of stable mixed-ligand zinc phosphite with genuine pores has been synthesized by using zinc metal, inorganic phosphite acid, thio-functionalized O-donor (2,5-thiophenedicarboxylate, TPDC), and tetradentate N-donor [1,2,4,5-tetrakis(imidazol-1-ylmethyl)benzene, TIMB] units assembled into one crystalline structure according to a hydro(solvo)thermal method. This is a very rare case of a metal phosphite incorporating both N- and O-donor ligands. The tetradentate TIMB linker bound to zinc atoms of the isolated zincophosphite hexamers to form a 3D open-framework structure by crosslinking structural components of 1D chains and 2D layers. Here, the TPDC ligand acts as a monodentate binding model to functionalize its porous structure with the uncoordinated S atom and COO- group. Interestingly, this compound demonstrates the highest H2 storage capacity among organic-inorganic hybrid metal phosphates (and phosphites), and a good CO2 capture at 298 K compared with the majority of crystalline materials. The possible adsorption sites and selectivity for CO2 over H2 , N2 , and CO at 298 K were calculated by using density functional theory (DFT), the ideal adsorption solution theory (IAST), and fitting experimental pure-component adsorption data.

A Cd(II) Luminescent Coordination Grid as a Multiresponsive Fluorescence Sensor for Cr(VI) Oxyanions and Cr(III), Fe(III), and Al(III) in Aqueous Medium.

Hydro(solvo)thermal reactions of Cd(NO3)2, N-(pyridin-3-ylmethyl)-4-(pyridin-4-yl)-1,8-naphthalimide (NI-mbpy-34), and 5-bromobenzene-1,3-dicarboxylic acid (Br-1,3-H2bdc) afforded a luminescent coordination polymer, {[Cd(Br-1,3-bdc)(NI-mbpy-34)(H2O)]∙2H2O}n (1). Single-crystal X-ray diffraction analysis showed that 1 features a two-dimensional (2-D) gridlike sql layer with the point symbol of (44·62), where the Cd(II) center adopts a {CdO5N2} pentagonal bipyramidal geometry. Thermogravimetric (TG) analysis confirmed the thermal stability of 1 up to about 340 °C, whereas XRPD patterns proved the maintenance of crystallinity and framework integrity of 1 in CH2Cl2, H2O, CH3OH, and toluene. Photoluminescence studies indicated that 1 displayed intense blue fluorescence emissions in both solid-state and H2O suspension-phase. Owing to the good fluorescent properties, 1 could serve as an excellent turn-off fluorescence sensor for selective and sensitive Cr(VI) detection in water, with LOD = 15.15 µM for CrO42- and 14.91 µM for Cr2O72-, through energy competition absorption mechanism. In addition, 1 could also sensitively detect Cr3+, Fe3+, and Al3+ ions in aqueous medium via fluorescence-enhancement responses, with LOD = 2.81 µM for Cr3+, 3.82 µM for Fe3+, and 3.37 µM for Al3+, mainly through an absorbance-caused enhancement (ACE) mechanism.

Recent developments in organic-inorganic hybrid metal phosphates and phosphites.

The design and synthesis of crystalline materials have been a subject of intensive research because of their interesting structures, physicochemical properties, and potential applications. However, the crystalline structure of organic-inorganic hybrid materials collapses to lose the structural features of the original networks and/or frameworks when exposed to different stimuli such as pH, vapor, water, high temperature, and organic solvents. This hampers further studies focusing on practical applications. Although several review articles provide reasonable pathways for the preparation of stable metal-organic frameworks (MOFs) and coordination polymers (CPs), the synthesis and design of stable materials containing organic species remain challenging. In this frontier article, we discuss the development of crystalline MOF, CP, metallophosphate, and metallophosphite materials, and provide a feasible approach for the formation of stable organic-inorganic hybrid compounds that combine MOFs (or CPs) and phosphate (or phosphite) building elements. In addition to their interesting structures, the synthetic strategies and structural stabilities of such hybrid composites are also presented.

Stable Crystalline Organic-Inorganic Hybrid Indium Phosphate with Dye Removal and Ractopamine Detection Applications.

A highly stable framework of an organic-inorganic hybrid indium phosphate (NTOU-7) was synthesized under hydro(solvo)thermal conditions and structurally characterized by single-crystal X-ray diffraction and solid-state NMR spectroscopy. This is the first example of a post-transition-metal phosphate incorporating tetradentate organic molecules. The In atoms in the inorganic layers are coordinated by imidazole rings of the 1,2,4,5-tetrakis(imidazol-1-ylmethyl)benzene linkers to generate a new solid-state material. NTOU-7 showed high chemical stability and displayed excellent performance for both dye removal and ractopamine (RAC) detection, which are interesting environmental and biosensing applications. The sensitivity and ultralow limit of detection were 607.9 µA·µM·cm-2 and 2.74 × 10-10 mol·L-1 (0.08 ppb), which meet the requirements stated by the Codex Alimentarius Commission (10 ppb RAC residue in beef and pork). The detection performance was confirmed by sensing spiked-in RAC in real pork samples. We also reported the synthesis, characterization, structural stability, dye removal, and sensing properties of NTOU-7.

A thio-functionalized zinc phosphite with a large-channel framework and enhanced removal ability of mercury ion from aqueous solutions.

The first example of a thio-functionalized zincophosphite material (NTOU-2S) incorporating the 2,5-thiophenedicarboxylate (TPDC) ligands was synthesized using a hydro(solvo)thermal method and structurally characterized by single-crystal X-ray diffraction. Interestingly, the perspective view of the crystal structure for NTOU-2S is similar to our previous report of NTOU-2 but the carboxylate organic ligands (TPDC for NTOU-2S; 1,4-benzenedicarboxylate, BDC, for NTOU-2) in both compounds adopt different types of bis-monodentate coordination models (the unusual cis bonding versus a trans linkage) to bridge the metal atoms of inorganic tubes in the formation of large-channel zincophosphite frameworks, resulting in structural and functional diversities. The thiophene-based compound also displayed higher thermal stability and removal ability for the softer Hg2+ cations from water solutions than the performance of sulfur-free NTOU-2. In addition, the synthesis, structural characteristics, removal properties of heavy metal cations, and thermal and chemical stabilities for both compounds were also reported.

Zinc(II)-Organic Framework Films with Thermochromic and Solvatochromic Applications.

Multiple-stimuli-responsive photoluminescence films based on a ZnII -organic framework, {[Zn2 (Htpim)(3,4-pydc)2 ]⋅4 DMF⋅4 H2 O}n (1, Htpim=2,4,5-tri(4-pyridyl)imidazole, 3,4-H2 pydc=3,4-pyridinedicarboxylic acid), were fabricated. This compound consisted of a 2D corrugated layer, {Zn(3,4-pydc)}n , which was further pillared using a Y-shaped pillar N-donor ligand (Htpim) to form a 3D-pillared-layer framework with 1D open channels. The rectangular channels in the as-synthesized compound are fully occupied by guest DMF and H2 O molecules. The framework exhibits instant and reversible thermochromic properties corresponding to the removal of different H2 O and DMF guest molecules as temperature increases. The pale-yellow crystal undergoes significant redshifting to a greenish emission centered at 530 nm. Compound 1 also showed remarkable solvatochromic effects in the presence of various organic solvents without affecting its structural integrity. In addition, polycrystalline MOF films were grown on an α-Al2 O3 support for switchable and fast-response thermochromic and solvatochromic sensors.

A dual fluorescent/phosphorescent zincophosphite with interesting water adsorption and structural transformation properties.

A dual fluorescent/phosphorescent solid was produced using the triazole-assisted synthesis method under hydro(solvo)thermal conditions. The title compound emitted blue luminescence that turned green when UV irradiation was stopped. It also exhibited stable PL properties with good thermal and photostability. Furthermore, the 3D inorganic skeleton in NTOU-6 underwent structural transformation into another inorganic metallophosphite solid (NTOU-6b) and water adsorption was observed during this process of structural reconstruction. The detailed structural features of both compounds were also determined by single-crystal X-ray diffraction. This is a very rare example of a metallophosphite with the interesting properties of luminescence color switching (blue to green), water adsorption, and structural transformation. The synthesis, structural diversity, adsorption, material stability, and luminescence properties were also discussed.

An Unprecedented Interpenetrating Structure Built from Two Differently Bonded Frameworks: Synthesis, Characteristics, and Efficient Removal of Anionic Dyes from Aqueous Solutions.

The first example of one single crystal (NTOU-5) containing two different organic-inorganic hybrid open-framework structures was obtained using a hydro(solvo)thermal method and structurally characterized by single-crystal X-ray diffraction. Remarkably, under the same synthetic conditions, the zinc ions are respectively coordinated by oxalic acid (OX) and 1,2,4,5-tetrakis(imidazol-1-ylmethyl)benzene (TIMB) linkers to form two significantly different frameworks: anionic [Zn2 (OX)3 ]2- and cationic [Zn(TIMB)]2+ networks that interweave with each other to give an unprecedented interpenetrating structure with two differently-bonded open-frameworks. From the inorganic chemistry perspective, it is extremely difficult to control to which metal center the oxygen-donor linkers or/and nitrogen-donor ligands bind. A mixed Co/Zn analogue was also obtained by a similar method. The single-crystal XRD and EDS analyses indicate that the octahedral Zn ions of the anionic framework are replaced by cobalt cations, whereas the Zn ions in the tetrahedral positions of the cationic networks remain intact. This leads to the formation of the interpenetrating analogue with a mixed metal composition. Furthermore, NTOU-5 shows structural stability and efficiently removes organic dyes from aqueous solutions at concentrations of 10 ppm.

Rare metal-ion metathesis of a tetrahedral Zn(ii) core of a noncentrosymmetric (3,4)-connected 3D MOF.

An SHG-active noncentrosymmetric (3,4)-connected Zn(ii)-organic framework, {[Zn2(4-abpt)(3,4-pydc)2]·2DMAc·3MeOH·H2O}n (1-Zn), was synthesized using a mixed-ligand system. The 1-Zn framework undergoes metal metathesis, with the complete exchange of the tetrahedrally coordinated ZnII ions with CuII ions while retaining the integrity of the network.

A Highly Stable Framework of Crystalline Zinc Phosphite with Selective Removal, Recovery, and Turn-On Sensing Abilities for Mercury Cations in Aqueous Solutions.

A highly stable framework of organic-inorganic hybrid zinc phosphite (NTOU-4) and its cobalt analogue (NTOU-4a) were synthesized under the hydro(solvo)thermal conditions and structurally characterized by single-crystal X-ray diffraction. Their frameworks consisted of inorganic metallophosphite chains, in which the metal atoms were interlinked through 1H-1,2,4-triazole-3,5-diamine and 1,4-benzenedicarboxylate linkers to form new crystalline materials. It is extremely difficult to achieve the consolidation of three distinct coordinations of metal-carboxylate, metal-triazolate, and metal-phosphite bonds into one crystal, resulting in the synthesis of the first mixed-ligand terephthalate-metallophosphite solids in the absence of organic molecules as templates or space-filling counters in their structures. Interestingly, the zinc compound not only exhibits high thermal stability (up to 400 °C in air) and chemical resistance to seawater, aqueous solutions (pH 3-11), and organic solvents at boiling conditions, but also shows selective removal, recovery, and "turn-on" sensing abilities of toxic mercury ions in aqueous solutions. Furthermore, the synthesis, characterization, and the difference of the framework stabilities between isostructural zinc and cobalt compounds are also reported.

A Series of Organic-Inorganic Hybrid Zinc Phosphites Containing Extra-Large Channels.

A series of organic-inorganic hybrid zinc phosphites with extra-large channels were synthesized and characterized by single-crystal X-ray diffraction. This is an unusual example of introducing 1,4-benzenedicarboxylate and/or biphenyl-4,4'-dicarboxylate ligands into the organically templated metal phosphite system to build extra-large-channel zeolite-related materials via hydro(solvo)thermal reactions. Those frameworks are composed of carboxylate linkers and inorganic tubes of zinc phosphites, translating their channel windows from a square shape (NTOU-1) to rhombus forms (NTOU-2 and NTOU-3) via the replacement of organic amines or ligands under synthesis conditions otherwise identical with those used to prepare NTOU-1. The synthesis, structural diversity, photoluminescence, and adsorption properties for dye molecules and lanthanide ions are also reported.

Visual detection of cyanide ions by membrane-based nanozyme assay.

In this paper, we report a simple one-step synthesis of well-dispersed amorphous cobalt hydroxide/oxide-modified graphene oxide (CoOxH-GO) possessing peroxidase-like catalytic activity, and its application for the detection of H2O2, glucose, and CN- ions. CoOxH is formed and deposited in situ on the GO surface through the reaction between GO (size ~ 240nm) and Co2+ in basic solution at room temperature. We investigated the enzyme-mimicking activity of the CoOxH-GO nanohybrid in detail via the H2O2-mediated oxidation of Amplex Red (AR) to form fluorescent resorufin. The peroxidase-like activity of CoOxH-GO is utilized herein for the quantitation of H2O2 in a wide concentration range, from 100nM to 100µM. When coupled with glucose oxidase (GOD), the AR/CoOxH-GO system can determine glucose level in blood samples. Interestingly, cyanide ions (CN-) significantly inhibit the catalytic activity of the CoOxH-GO nanohybrid, which allows for the construction of a probe for the detection of CN- in water samples and laboratory wastes. We fabricated a membrane-based CoOxH-GO probe for the visual detection of CN- by preparing a thin film of CoOxH-GO on a positively charged and porous nylon membrane (N+M). The CoOxH-GO/N+M operates on the principle that CN- inhibits the catalytic activity of CoOxH-GO towards the H2O2-mediated oxidation of AR to form reddish resorufin on the membrane. The intensity of the red color of the membrane decreases with increasing CN- concentration, which can be easily observed with the naked eye at the nanomolar level. This cost-effective sensing system allows for the rapid and simple determination of the concentrations of CN- in complicated wastewater samples.

Two Polymorphs of an Organic-Zincophosphate Incorporating a Terephthalate Bridging Ligand in an Unusual Bonding Mode.

Two new polymorphs of a zinc phosphate incorporating the terephthalate organic ligand 1,4-benzenedicarboxylate (BDC), (H2DA)Zn2(cis-BDC)(HPO4)2 (1) and (H2DA)Zn2(trans-BDC)(HPO4)2 (2), where DA = 1,7-diaminoheptane, were synthesized via a hydro(solvo)thermal method at different reaction temperatures and structurally characterized by single-crystal X-ray diffraction. Interestingly, the BDC ligands, which adopt the bis-monodentate coordination model with a unusual cis type for compound 1 and with a trans linkage for compound 2, bridge the Zn atoms of the inorganic layers in the generation of two polymorphs with structural diversities (one kind of arrangement of the layered zincophosphate layer in 1; the flat and zigzag sheets of inorganic networks in 2). A simple method for tuning the optical luminescence of the title compound from blue, red, green, yellow, and pink to white emission by stirring powdered samples in lanthanide-cation-containing aqueous ethanol solutions at room temperature for 1-2 h is also presented.

New 3 D Tubular Porous Structure of an Organic-Zincophosphite Framework with Interesting Gas Adsorption and Luminescence Properties.

A new 3D tubular zinc phosphite, Zn2 (C22 H22 N8 )0.5 (HPO3 )2 ⋅H2 O (1), incorporating a tetradentate organic ligand was synthesized under hydro(solvo)thermal conditions and structurally characterized by single-crystal X-ray diffraction. Compound 1 is the first example of inorganic zincophosphite chains being interlinked through 1,2,4,5-tetrakis(imidazol-1-ylmethyl)benzene to form a tubular porous framework with unusual organic-inorganic hybrid channels. The thermal and chemical stabilities, high capacity for CO2 adsorption compared to that for N2 adsorption, and interesting optical properties of LED devices fabricated using this compound were also studied.

New hybrid organic-zincophosphate frameworks: single-crystal-to-single-crystal structural transformation and remarkable thermal and chemical stabilities.

This research is the first example of a hybrid metal phosphate that undergoes an SCSC structural transformation and provides a new route for the synthesis of organic-inorganic hybrid materials with high stabilities via the introduction of nitrogen-donor ligands into a metal-phosphate system. The synthesis, structural diversity, and thermal and chemical stabilities are also discussed.