Design and Construction of the Uranyl Coordination Polymer with Multifunction Stimulus Response: Fluorescent Sensors for Halide Ions and Photochromism.

It can provide ideas for the use of uranium elements in the treatment of spent fuel from nuclear wastewater to explore the application potential of uranium element. Thus, it is necessary to research the structure and properties of a novel uranyl coordination polymer (CP) for uranium recovery and reuse. Herein, we designed and prepared a new uranyl CP U-CMNDI based on UO22+ and H2CMNDI (H2CMNDI = N, N'-bis(carboxymethyl)-1,4,5,8-naphthalenediimide). Structural analysis shows that two uranyl ions are connected by two parallel deprotonated CMNDI ligands to form a discrete uranyl dimer structure. U-CMNDI can act as a potential stimulus-responsive halide ion sensor by a fluorescence "turn on" response in water. The limit of detection for fluoride (F-), bromide (Br-), iodide (I-), and chloride (Cl-) is 5.00, 5.32, 5.49, and 5.73 µM, respectively. The fluorescence "turn on" behavior is based on the photoinduced electron transfer (PET) mechanism between halide ions and electron-deficient NDI cores. In addition, U-CMNDI demonstrates a color response to ultraviolet light, exhibiting reversible photochromic behavior with a notable color change. The color change mechanism can contribute to the PET process and the radical process.

Stimulus-Responsive Lanthanide MOF Materials Encapsulated with Viologen Derivatives: Characterization, Photophysical Properties and Sensing on Nitrophenols.

Viologens (1,1'-disubstituted 4,4'-bipyridyls) possessing electron-deficient properties and redox activity are a class of suitable chromophores to assemble metal-organic hybrid photochromic materials. Thus, viologen-functionalized metal-organic frameworks (MOFs) have attracted much attention for their photochromic properties; however, the syntheses of lanthanide-viologen hybrid crystalline photochromic materials still face many challenges. For example, the structures and properties of the final products are difficult to predict and are limited by molecular configurations. In this work, host-guest composite-material Ln-NH2 BDC-pbpy MOFs were constructed by encapsulating viologen derivative pbpyCl2 . The pbpy2+ moieties are uniformly embed by their π-π conjugation in the pores of the 3D structure by electrostatic interactions. Due to the encapsulation of the chromophore pbpy2+ moieties, Ln-NH2 BDC-pbpy MOFs have reversible photochromic properties: they can change color after irradiation and can return to the original color after being protected from light or heating. Interestingly, the fluorescence intensity decreases with illumination time and recovers in the dark. As a result, Ln-NH2 BDC-pbpy MOFs show both photochromic and photomodulated fluorescence. Based on the outstanding fluorescence performance of the Ln-NH2 BDC-pbpy MOFs, they also show a wonderful effect for detecting nitrophenols, especially TNP.

Multiple Stimulus Response 2D Framework Constructed by a Flexible Cyclotriphosphazene-Derived Carboxylic Acid Linker: Synthesis, Characterization, and Fluorescence Sensing to Phenolic Pollutants and Small-Molecule Drugs.

Hexachlorocyclotriphosphazene is one of the most representative phosphazene compounds which have been proved to have broad application prospects in many fields. However, it is an emerging research perspective to combine cyclotriphosphazene-derived polycarboxylic acid compounds with lanthanides for the construction of Tb-DPCP metal-organic framework (MOF) materials. Herein, a Tb-DPCP MOF, (CH3)2NH2[Tb3(HDPCP)(DMF)(H2O)3]·6DMF (1), was successfully prepared via the reaction of H12HDPCP [hexa(4-carboxyphenoxy) cyclotriphosphazene] and Tb(NO3)3·6H2O under the solvothermal condition. Through fluorescence sensing experiments, it was found that both nitrophenols and chlorophenols could cause the fluorescence quenching of compound 1. At the same time, the compound also exhibited nice trace detection ability for small-molecule drugs (moxifloxacin hydrochloride, balsalazide disodium, and colchicine); the limits of detection were all lower than 0.2 µM. These experimental results fully demonstrated the potential application value of 1 as a multifunctional fluorescent sensor.

Preparation of Naphthalenediimide-Decorated Electron-Deficient Photochromic Lanthanide (III)-MOF and Paper Strip as Multifunctional Recognition and Ratiometric Luminescent Turn-On Sensors for Amines and Pesticides.

Detecting toxic amine and pesticide contamination in the environment is one of the most pressing issues for environmental sustainability. In this work, two 3D Ln-BINDI complexes [Ln = Eu (1), Sm (2); H4BINDI (N, N'-bis(5-isophthalic acid)-1,4,5,8-naphthalenediimide)] have been designed and synthesized. Crystal structure of [Eu2(BINDI) (NO3)2(DMA)4]·2DMA (complex 1) featuring the lvt topology was determined by X-ray single-crystal diffraction. A multi-functional ratiometric luminescence sensor benefitting from π-electron-deficient NDI moieties and f-f transition characteristics of lanthanide Eu3+ ions for complex 1 has been investigated. Markedly, complex 1 exhibit completely different selective fluorescence ratiometric turn-on responses and pretty high sensitivity behaviors to aromatic amines (OPD), aliphatic amines (n-BA), and pesticides (TBZ), respectively, which are driven by interactions between the electron-donating amino group and acceptor NDI site, contributing to complex 1 as a potential ratiometric luminescent turn-on sensor for practical environmental applications. A PVA/1@paper strip can be used as a potential size selectivity sensor for the practical detection of aliphatic amine vapors in the environment through visual chromic fluorescence enhancement. Because NDIs can undergo one-electron reduction to form stable NDI· free radicals, solid complex 1 can visually distinguish different kinds of amines by selective amine-specific color changes and has the photochromic property of erasable inkless printing.

RhB-Embedded Mn-MOF with Cyclotriphosphazene Skeleton as Dual-Emission Sensor for Putrescine as well as Smart Fluorescent Response of Aromatic Diamines and Nitrophenol.

Luminescent metal-organic framework composites with multiple luminescence emissions have been efficient sensing platforms. Herein, a fluorescent sensor (RhB@1-0.4) with dual-emission fluorescence properties was prepared by introducing rhodamine B (RhB) into the framework of complex 1, [Mn2.5(HCPCP)(H2O)4]·(CH3CN)0.5 [HCPCP = hexa-(4-carboxyl-phenoxy)-cyclotriphosphazene and CH3CN = acetonitrile), which is a novel crystalline two-dimensional (2D) coordinated organic framework material. It is a highly desirable material, realizing a ratiometric fluorescence response to putrescine with a high signal-to-noise ratio, and the detection limit can be as low as 6.8 µM. In addition, RhB@1-0.4 exhibited a better fluorescent sensing performance for aromatic diamines and nitrophenols compared with that of complex 1. It is a potential functionalized MOF material for the application of multichannel fluorescence sensing.

Stimuli-Responsive Naphthalenediimide Cd-MOFs Tuned by Different Aliphatic Dicarboxylic Acids with Extended Spacers.

A series of novel Cd metal-organic frameworks (MOFs) (1-9) with different extended spacers with seven kinds of the aliphatic dicarboxylic acids as secondary building linkers based on N,N'-di(4-pyridylacylamino)-1,4,5,8-naphthalenediimide (NDI-A) have been designed and synthesized by changing the volume ratio of solvents under solvothermal conditions. In addition, the secondary building linkers of aliphatic dicarboxylic acids have different spacer lengths, resulting in different structures of complexes 1-9. So, their packing structures are affected by the degree of distortion of the NDI-A ligand, the different aliphatic dicarboxylic acids ligands, and the hydrogen-bonding patterns. Complexes 1-9 showed stimuli-responsive emission tuned by different aliphatic dicarboxylic acids with extended length spacers under UV light irradiation, accompanied by the color change from light orange to dark brown, and achieved reversible photochromic under heating, which indicates that they could serve as secret erasable inks. Moreover, complexes 1-9 exhibited selective vaporchromic behavior to methylamine (MA), and the vaporchromic sample could be recovered after washing with MeOH. It is worth noting that the preparation of poly(vinyl alcohol) (PVA)-NDI-MOF films enables the photochromic and vaporchromic properties of complexes 1-9 to apply in practice. In addition, complexes 1-9 exhibited good fluorescence properties as sensing probes toward 2,4,6-trinitrophenol (TNP) with lower limits of detection. In short, this work provides a broad field to explore the creative NDI-MOF materials with photoactive and luminescent properties.

Construction of Large-Scale Conjugated Functionalized Cyclotriphosphazene Lanthanide Framework for Selective Sensing of Volatile Organic Compounds and Assembly of Color-Tunable Dye-Encapsulated Composites.

A flexible functionalized cyclotriphosphazene hexacarboxylic acid, hexakis(4-carboxylatephenoxy) cyclotriphosphazene (HCPCP), is used for the synthesis of a family of fluorescent Ln-HCPCP frameworks (Ln = La, Pr, Nd, Gd, and Ho). Structural analysis shows that the compounds exhibit 3D structures with [Ln3(COO)10], secondary building units formed by Ln-O-C-O-Ln connection. Then the molecules are connected to each other through HCPCP, forming rectangular channels along the c-direction. Interestingly, the fluorescence sensing studies show that compound 1 could be used as a multifunctional fluorescence sensor toward volatile organic compounds via different fluorescence emission behaviors. Moreover, a series of Dye@La-HCPCP composites (Dye = rhodamine B, safranine T, crystal violet, and malachite green) are successfully prepared with different quantum yields by the solvothermal reaction followed by cation exchanges.

Cage Bismuth Metal-Organic Framework Materials Based on a Flexible Triazine-Polycarboxylic Acid: Subgram Synthesis, Application for Sensing, and White Light Tuning.

Bismuth-based metal-organic frameworks (MOFs) have always attracted the attention of many researchers. Here, we first report a crystalline Bi-MOF (Bi-TDPAT) based on a flexible triazine-polycarboxylic linker 2,4,6-tris(3,5-dicarboxylphenylamino)-1,3,5-triazine (H6TDPAT) and bismuth nitrate; its crystallite quality is adequately good and the diffraction data can be collected directly by single crystal X-ray diffraction rather than 3D electron diffraction. The structure of Bi-TDPAT belongs to a novel topology type btt. Notably, the synthesis scale of Bi-TDPAT can be expanded, and sub-gram synthesis can be realized. At the same time, we synthesized a microcrystalline material Bi-TATAB utilizing 2,4,6-tris(4-carboxylphenylamino)-1,3,5-triazine (H3TATAB). The structures of the two materials were characterized by several microanalysis tools. Considering that Bi-TDPAT is a blue light-emitting material with a broad emission peak, we prepared a white light emitting composite material Eu/Tb@Bi-TDPAT by encapsulating Eu(III)/Tb(III) in Bi-TDPAT. In addition, the fluorescence sensing functions of Bi-TDPAT and Bi-TATAB were explored. The results showed that they could detect and recognize various nitrophenols, and the optimal limit of detection is as low as 0.21 µM, which can be reused even after five cycles. Energy competitive absorption (CA) and photo-induced electron transfer are the main sensing mechanisms. By comparing and analyzing the properties of these two bismuth-based crystalline materials, we believe that this work also provides inspiration for the synthesis and development of bismuth-based MOF in the future.

High-Symmetry Co/Ni Triazine Polycarboxylate Diverse Frameworks Constructed by Mx(COO)y Building Blocks: Characterization and Catalytic Performance Evaluation of p-Nitrophenol.

Three new triazine compounds [Co1.5(H3TDPAT)(H2O)3]·6H2O (1), [Co2(TCPT)(µ2-H2O)2]·OH (2), and [Ni3(TCPT)]·3OH (3) were designed and synthesized via the reaction of the symmetrical triazine ligand connected by C-N-C and C-O-C bonds with triazine poly(carboxylic acid)s ligands as the side arms: H6TDPAT (H6TDPAT = 2,4,6-tris(3,5-dicarboxylphenylamino)-1,3,5-triazine) and H3TCPT (H3TCPT = 2,4,6-tris(4-carboxyphenoxy)-1,3,5-triazine) as well as the corresponding metal salts under the solvothermal condition. Three triazine polycarboxylate frameworks were characterized by elemental analysis, infrared spectroscopy, ultraviolet spectroscopy, thermogravimetric analysis, X-ray powder diffraction, and solid fluorescent spectra in detail. The structural analysis results showed that the three-dimensional porous cage framework of compound 1 was constructed by three different polyhedral cages connected with [Co(COO)4(H2O)2] building blocks. One of the compounds, 2, is formed by twin propeller Co2(µ2-H2O)(COO)3 building blocks connecting two-dimensional layers and the intermolecular π-π interactions involved the triazine rings between the layers. While the structure of compound 3 is similar to that of 2, assembly is by Ni(COO)3 building blocks and adjacent layers of the face-to-face π-π interaction between the triazine rings. In order to explore functional properties, the catalytic reduction of p-nitrophenol (PNP) of compounds 1-3 was investigated. They exhibit excellent catalytic activity of more than 95% for reduction of PNP with a dose of 2.5 mg of the compounds.

Spin-Orbit Charge-Transfer Intersystem Crossing in Anthracene-Perylenebisimide Compact Electron Donor-Acceptor Dyads and Triads and Photochemical Dianion Formation.

Perylenebisimide (PBI)-anthracene (AN) donor-acceptor dyads/triad were prepared to investigate spin-orbit charge-transfer intersystem crossing (SOCT-ISC). Molecular conformation was controlled by connecting PBI units to the 2- or 9-position of the AN moiety. Steady-state, time-resolved transient absorption and emission spectroscopy revealed that chromophore orientation, electronic coupling, and dihedral angle between donor and acceptor exert a significant effect on the photophysical property. The dyad PBI-9-AN with orthogonal geometry shows weak ground-state coupling and efficient intersystem crossing (ISC, ΦΔ =86 %) as compared with PBI-2-AN (ΦΔ =57 %), which has a more coplanar geometry. By nanosecond transient absorption spectroscopy, a long-lived PBI localized triplet state was observed (τT =139 µs). Time-resolved EPR spectroscopy demonstrated that the electron spin polarization pattern of the triplet state is sensitive to the geometry and number of AN units attached to PBI. Reversible and stepwise generation of near-IR-absorbing PBI radical anion (PBI-⋅ ) and dianion (PBI2- ) was observed on photoexcitation in the presence of triethanolamine, and it was confirmed that selective photoexcitation at the near-IR absorption bands of PBI.- is unable to produce PBI2- .

Integrated Photoresponsive Alkaline Earth Metal Coordination Networks: Synthesis, Topology, Photochromism and Photoluminescence Investigation.

Photoresponsive materials are a key part of the age of smart technology that have potential in a broad range of applications. Coordination networks (CNs) are widely used due to their designability and stability. In this work, three novel alkaline earth metal coordination networks (AEM-CNs): [Mg(CMNDI)(H2 O)2 ], [Ca(CMNDI)(H2 O)2 ]⋅H2 O, and [Sr(CMNDI)(H2 O)(DMF)] with fsl, cds, and scn topology nets were synthetized via N,N'-bis(carboxymethyl)-1,4,5,8-naphthalenediimide (H2 CMNDI); the scn net is not found in the Reticular Chemistry Structure Resource or ToposPro. The reusable and sensitive photochromic properties of the three CNs enable them to be used as secret inks or ultraviolet detectors. In addition, the CNs also exhibited reusable photoluminescent turn-off toward the drug molecules, balsalazide disodium (Bal.) and colchicine (Col.), with good limits of detection of 0.16 and 0.70 µM. To the best of our knowledge, this is the first study of a fluorescence sensor for Bal. Thus, the AEM-CNs provide a design idea for integrated photoresponsive materials that could be further improved in the near future by further study.

Cu-MOF Material Constructed with a Triazine Polycarboxylate Skeleton: Multifunctional Identify and Microdetecting of the Aromatic Diamine Family (o,m,p-Phenylenediamine) Based on the Luminescent Response.

Organic aromatic amines are widely used in various fields such as pharmaceuticals, pesticides, dyes, and tobacco smoke. The pollution of organic amines has become a problem that cannot be ignored, due to the extensive harmful effects on the environment and public health, which has become one of the most concerned frontier fields in the world. Identifying and microdetecting o-phenylenediamine (OPD), m-phenylenediamine (MPD), and p-phenylenediamine (PPD) using MOFs have rarely been reported. On the basis of the blue emission properties of Cu-TBDA constructed with 5,5'-((6-chloro-1,3,5-triazine-2,4-diyl)bis(azanediyl))diisophthalic acid (H4TBDA) ligand, Cu-TBDA was studied primarily to identify and detect aromatic diamine family as a multifunctional chemical sensor. Interestingly, Cu-TBDA has a very high selectivity and sensitivity to OPD and MPD with a low limit of detection (5.00 µM for OPD and 1.77 µM for MPD). Especially for OPD, Cu-TBDA has a unique switching function for it. When the concentration of OPD is less than 9.1 × 10-4 M, the fluorescence response of Cu-TBDA suspension exhibit enhanced. However, when the concentration of OPD is more than 9.1 × 10-4 M, the emission intensity displays quenching phenomenon. Therefore, Cu-TBDA as a chemical sensor not only has recognition and detection functions for organic aromatic amines but also first exhibits turn-on and -off sensing behavior toward OPD.

Three Pbx(COO)y Cluster Frameworks Based on a Flexible Triazinetricarboxylic Acid Ligand: Syntheses, Structures, and Fluorescent Sensing Application for Nitrophenols.

Three new metal-organic frameworks (MOFs), namely, [Pb7(TTPCA)4Cl2]·3H2O (1), [Pb7(TTPCA)4(DMA)2(HCOO)2]·H2O (2), and [Pb4(TTPCA)3]·3DMF·2H2O·H3O (3), were synthesized by the H3TTPCA ligand [H3TTPCA = 1,1',1″-(1,3,5-triazine-2,4,6-triyl)-tripiperidine-4-carboxylic acid], with lead(II) nitrate under solvothermal conditions. They were characterized by CHN analysis, IR spectroscopy, UV-vis spectroscopy, and single-crystal and powder X-ray diffraction. In addition, their thermogravimetric analysis and fluorescence properties were studied. Compounds 1-3 were 3D MOF structures with different Pbx(COO)y clusters: ([Pb7(COO)12Cl2]), ([Pb7(COO)12]), and [Pb8(COO)18]. Fluorescence detection of compounds 1-3 shows that they can act as excellent sensors of nitrophenols with a low limit of detection and a high quenching constant.

Thorium-Organic Framework Constructed with a Semirigid Triazine Hexacarboxylic Acid Ligand: Unique Structure with Thorium Oxide Wheel Clusters and Iodine Adsorption Behavior.

We successfully prepared and characterized a distinctive thorium-based MOF (metal-organic framework) Th-TTHA with thorium oxide wheel clusters under the conditions of solvothermal synthesis by utilizing thorium nitrate and semirigid triazine hexacarboxylic acid linker H6TTHA (H6TTHA = 1,3,5-triazine-2,4,6-triamine hexaacetic acid). To the best of our knowledge, Th-TTHA is the first thorium-based MOF assembled by semirigid triazine hexapod ligand H6TTHA. It is worth mentioning that Th-TTHA exhibits a novel and distinctive arrangement of structure and topology. Th-TTHA has abundant adsorption sites such as the triazine ring that is rich in nitrogen atoms, N of NH-, and carboxyl oxygen atoms without coordination with a central metal, which drove us to explore its iodine adsorption capacity. The experimental results show that Th-TTHA shows excellent adsorption capacity for iodine, and the adsorption amount in a saturated iodine cyclohexane solution can reach 528 mg/g within 24 h. This work is greatly significant for the development of new structures of thorium-based MOFs and the expansion of its functional characteristics, which is very essential for our in-depth understanding of thorium chemistry and in the management and disposal of radionuclides and application of the nuclear fuel cycle.

Polyiodine-Modified 1,3,5-Benzenetricarboxylic Acid Framework Zn(II)/Cd(II) Complexes as Highly Selective Fluorescence Sensors for Thiamine Hydrochloride, NACs, and Fe3+/Zn2.

Four new complexes, [Zn(TIBTC)(DMA)]·[NH2(CH3)2] (1), [Cd(TIBTC)(H2O)]·[NH2(CH3)2]·DMA (2), [Cd2(TIBTC)(2,2'-bipy)2(HCOO)] (3), and [Cd2(DIBTC)(2,2'-bipy)2(HCOO)] (4) (H3TIBTC = 2,4,6-triiodo-1,3,5-benzenetricarboxylic acid, H3DIBTC = 2,4-diiodo-1,3,5-benzenetricarboxylic acid, 2,2'-bipy = 2,2'-bipyridine, and DMA = dimethylacetamide), were successfully synthesized and characterized by elemental analysis, powder X-ray diffraction, infrared spectroscopy, ultraviolet-visible spectroscopy, and thermogravimetric analysis. Complexes 1 and 2 are three-dimensional supramolecular network structures, while complex 4 has a two-dimensional network structure. We preliminarily studied the fluorescence properties of the complexes and found that complexes 1-3 can detect thiamine hydrochloride, NACs, and Fe3+/Zn2+ with high sensitivity and selectivity.

A Uranyl-Organic Framework Featuring Two-Dimensional Graphene-like Layered Topology for Efficient Iodine and Dyes Capture.

A novel uranyl-organic framework [(CH3)2NH2][UO2(TATAB)]·2DMF·4H2O (U-TATAB) was assembled through the solvothermal synthesis of UO2(CH3COO)2·2H2O and triazine tricarboxylate linker H3TATAB (H3TATAB = 4,4',4″-s-triazine-1,3,5-triyltri- p-aminobenzoate). It was characterized by single-crystal X-ray diffraction, elemental analysis, IR, powder X-ray diffraction, and thermogravimetric microanalysis. It is worth mentioning that U-TATAB exhibits an original arrangement of structures with interesting topology. Structural analysis confirmed that U-TATAB displays an interesting two-dimensional graphene-like layered topology. In order to broaden its functional characteristics, we first investigated the functional adsorbent U-TATAB for iodine capture in cyclohexane solution and for the removal of dye in aqueous solution. Large porosity, unique structure character, and the π-electron walls made of TATAB make the material a promising functional absorbent exhibiting excellent adsorption performance for iodine and dye molecules. Most notably, this is the first case of a uranyl-organic framework built by secondary building unit (SBU) [UO2(RCOO)3]- and extended trigonal triazine tricarboxylate ligand H3TATAB with amino functional groups.

Triazine Poly(carboxylic acid) Metal-Organic Frameworks and the Fluorescent Response with Lead Oxygen Clusters: [Pb7(COO)12X2] by Halogen Tuning (X = Cl, Br, or I).

A series of novel metal-organic frameworks were synthesized by using semirigid ligand 1,1',1″-(1,3,5-triazine-2,4,6-triyl)tripiperidine-4-carboxylic acid (H3TTPCA) and lead halide (Cl, Br, or I). The three complexes were characterized by elemental analysis, infrared spectroscopy, ultraviolet-visible spectroscopy, powder X-ray diffraction analysis, and thermogravimetric analysis. X-ray single-crystal diffraction analysis demonstrated that all three complexes were three-dimensional inorganic-organic framework structures with Pb-X2 (X = Cl, Br, or I). However, slight differences in the chemical environment were the focus of the coordinated halogen atoms and the different compositions of metal oxygen clusters: [Pb7(COO)12Cl2], [Pb7(COO)12Br2], and [Pb7(COO)12I2]. Because of the fluorescence of the organic ligand, the three complexes showed similar photoluminescence properties at room temperature, but the intensity of emissions decreased gradually with an increase in the atomic radius of coordinated halogen atoms. Interestingly, in the fluorescence response tests, complexes 1 and 2 displayed an optical signal of fluorescence "turn-on" while complex 3 showed an optical signal of fluorescence "turn-off". Here we aim to provide a possible mechanism to explain these unique and contradictory luminescence results.

Stable Lanthanide-Organic Framework Materials Constructed by a Triazolyl Carboxylate Ligand: Multifunction Detection and White Luminescence Tuning.

Under hydrothermal conditions, we have successfully synthesized six isostructural lanthanide coordination polymers, [LnL1.5(H2O)2]·1.75H2O (1-6; Ln = Eu, La, Pr, Nd, Sm, Gd), by the reaction of 5-methyl-1-(4-carboxylphenyl)-1 H-1,2,3-triazole-4-carboxylic acid (H2L) and Ln(NO3)3·6H2O. Structural analysis shows that polymers 1-6 show novel three-dimensional supramolecular network structures. The luminescent properties for polymer 1 have been investigated at room temperature. The results have shown that polymer 1 can be used as a chemical sensor for multifunctional testing such as UO22+, Fe3+ ion detection, and small organic molecule detection because of its strong fluorescence properties. In particular, polymer 1 exhibits extremely high selectivity and sensitivity for the detection of Fe3+ ions. In addition, white-light emission is achieved through a reasonable tuning proportion by mixing Gd3+ and Eu3+.

Multifunctional uranyl hybrid materials: structural diversities as a function of pH, luminescence with potential nitrobenzene sensing, and photoelectric behavior as p-type semiconductors.

A series of uranyl-organic frameworks (UOFs), {[(UO2)2(H2TTHA)(H2O)]·4,4'-bipy·2H2O}n (1), {[(UO2)3(TTHA)(H2O)3]}n (2), and {[(UO2)5(TTHA) (HTTHA)(H2O)3]·H3O}n (3), have been obtained by the hydrothermal reaction of uranyl acetate with a flexible hexapodal ligand (1,3,5-triazine-2,4,6-triamine hexaacetic acid, H6TTHA). These compounds exhibited three distinct 3D self-assembly architectures as a function of pH by single-crystal structural analysis, although the used ligand was the same in each reaction. Surprisingly, all of the coordination modes of the H6TTHA ligand in this work are first discovered. Furthermore, the photoluminescent results showed that these compounds displayed high-sensitivity luminescent sensing functions for nitrobenzene. Additionally, the surface photovoltage spectroscopy and electric-field-induced surface photovoltage spectroscopy showed that compounds 1-3 could behave as p-type semiconductors.

Construction of a triazine polycarboxylate Co-MOF with flexible and rigid coordination arms as well as excellent catalytic reduction and adsorption properties.

A new compound [Co2(H2BATD)(DMF)2]·2.5DMF·0.5H2O (1) was synthesized from the triazine ligand H6BATD (H6BATD = 5,5'-(6-biscarboxymethylamino-1,3,5-triazine-2,4-diyl) bis (azadiyl), DMF = N,N-dimethylformamide) and Co(NO3)2·6H2O. Compound 1 was characterized using infrared spectroscopy, UV-vis spectroscopy, PXRD, and thermogravimetry. The three-dimensional network of compound 1 was further constructed using [Co2(COO)6] building blocks from the flexible coordination arms and the rigid coordination arms from the ligand. In terms of functional properties, compound 1 can be used for the catalytic reduction of p-nitrophenol (PNP) to p-aminophenol (PAP), and compound 1 with a dose of 1 mg showed good catalytic reduction properties, as well as a conversion rate of over 90%. Based on the unique π-electron wall and carboxyl groups in the H6BATD ligand that provide abundant adsorption sites, compound 1 can be used to adsorb iodine in cyclohexane solution.