Flame retardant, high mechanical strength, transparent and water-resistant epoxy composites modified with chitosan derivatives.

Adding bio-based flame retardants to improve the flame retardancy of polymer materials without sacrificing other properties is a great challenge. Herein, a novel flame-retardant CS-DOPA was prepared from chitosan and 10-hydroxy-9,10-dihydro-9-oza-10-phosphaphenanthrene-10-oxide by acid-base neutralization reaction and fully characterized. The 4 wt% CS-DOPA modified EP showed good flame retardancy in both gaseous and condensed phase. The peak heat release rate, total smoke production, CO production, and smoke production rate of EP composites containing 4 wt% CS-DOPA were reduced by 55 %, 34 %, 45 %, and 46 %, respectively, to pass the UL-94 V-1 rating with a limiting oxygen index of 34.1 %. The CS-DOPA contributes to the formation of the condensed phase of the thermo-oxidation-resistant high-quality char layer with non-flammable other and phosphorus-containing free radicals released in the gas phase. In addition, EP/4CS-DOPA has good water resistance, mechanical properties, and transparency, with tensile and flexural strength improved by 12.7 % and 13.9 %, respectively, and still has high strength even after water treatment. The present work provides a green and facile strategy to use chitosan as a main raw material to manufacture EP materials with high performance.

A novel molecularly expanded covalent triazine framework heterojunction with significantly enhanced molecular oxygen activation and photocatalysis performance under visible light.

The activation capacity of molecular oxygen is an important indicator to evaluate the photocatalytic efficiency of photocatalysts. In this paper, WS2 nanosheet was deposited on hyper-crosslinked CTF-1-G (obtained by molecular expansion from covalent triazine framework CTF-1) to form a C-GW heterojunction, which promoted the photodegradation of pollutants and the activation of molecular oxygen. This novel C-GW heterojunction exhibited excellent degradation property for organic pollutants (tetracycline (TC), rhodamine B (RhB)) and activating molecular oxygen under visible light irradiation. Among them, C-GW15 could degrade 98% of 20 ppm TC in 60 min and 99% of 30 ppm RhB in 30 min, and it had the highest hydrogen generation rate and hydrogen production amount in 4 hours, which were 8.74 mmol h-1 g-1 and 34.94 mmol g-1, respectively. Meanwhile, C-GW15 had the strongest 3,3',5,5'-tetramethylbenzidine oxidation capacity and could generate 1.83 µmol of ˙O2- in 60 min and the production of H2O2 was 20.8 µmol L-1 in 40 min. The results of this study clearly indicated that the combination of WS2 and CTF-1-G can enhance the visible light absorption capacity and photogenerated carrier separation efficiency, thus promoting the photocatalytic performance. Finally, a Z-type photocatalytic mechanism was proposed based on radical capture, molecular oxygen activation experiments and electron spin resonance analysis. These findings will extend the fundamental understanding of the Z-type photocatalytic mechanism and provide new opportunities for the rational design of CTF heterojunctions for the treatment of environmental pollution and clean energy conversion.

Study of Salidroside and Its Inflammation Targeting Emulsion Gel for Wound Repair.

Salidroside has been widely used in anti-tumor, cardiovascular, and cerebrovascular protection. However, there are few reports of its use for wound repair. Herein, salidroside inflammation-targeted emulsion gel and non-targeted emulsion gel were developed for wound repair. The inflammation-targeted emulsion gels showed an overall trend of better transdermal penetration and lower potential than non-targeted emulsion gels (-58.7 mV and -1.6 mV, respectively). The apparent improvement of the trauma surface was significant in each administration group. There was a significant difference in the rate of wound healing of the rats between each administration group and the model group at days 7 and 14. Pathological tissue sections showed that inflammatory cells in the epidermis, dermis, and basal layer were significantly reduced, and the granulation tissue was proliferated in the inflammation-targeted emulsion gel group and the non-targeted emulsion gel group. Regarding the expressions of EGF and bFGF, the expressions of bFGF and EGF in the tissues of the inflammation-targeted group at days 7, 14, or 21 were significantly higher than that of the non-targeted emulsion gel group and the model group, both of which were statistically significant compared with the model group (p < 0.05). These results demonstrated that salidroside has the potential as an alternative drug for wound repair.

MOF-derived CdS/CoO S-type heterojunctions for improving the efficiency of photocatalytic evolution.

The aggravating extreme climate changes and environmental pollution problems have stimulated the exploration of green alternatives to conventional fossil fuels and green environmental treatments. Photocatalysis is recognized as an outstanding green tool for solving the energy crisis and environmental rehabilitation issues. Restricted by the high cost of precious metals, researchers expect to obtain low-cost, efficient and stable photocatalysts. Herein, CdS materials were derived through MOFs and subsequently combined with CoO to form CdS/CoO heterojunctions. The catalytic ability was evaluated by the photocatalytic degradation of tetracycline hydrochloride (TC) and the photocatalytic production of hydrogen. With the integration of CoO, in terms of TC degradation, CdS/CoO heterojunctions can degrade over 90% of TC within 1 hour. In terms of hydrogen production, compared to CdS alone, the hydrogen production efficiency of the CdS/CoO heterojunction increased by 1.7 times. The initial analysis of the reasons for the enhancement of photocatalytic efficiency was conducted by TEM, XPS and other characterization means. Density functional theory (DFT) calculations verified the existence of a built-in electric field in the CdS/CoO heterojunction, which was the essential reason for the improved catalytic performance, and finally, the presence of ˙O2- and ˙OH in the photocatalytic system was demonstrated by the ESR technique. Based on the carrier separation/transfer pathway in the heterojunction, a simple and novel S-type heterojunction scheme was proposed.

Construction of a direct Z-scheme CeO2/UiO-66-NH2 heterojunction for boosting photocatalytic organic pollutant degradation and H2 evolution performance.

In this study, hollow CeO2 nanospheres were grown on UIO-66-NH2 nanosheets to form a novel CeO2/UiO-66-NH2 (abbreviation, CUx) Z-scheme heterojunction photocatalyst by calcination and hydrothermal method for hydrogen production and photocatalytic degradation of organic pollutants. Under visible light, the H2 generation rate of the CU0.50 composite was 5662.1 µmol g-1 h-1, which was 22 and 7 fold than that of pure CeO2 and pure UiO-66-NH2, respectively. In addition, compared with CeO2 and UiO-66-NH2, the as-prepared CUx composites exhibited enhanced photo-degradation efficiencies for tetracycline (TC) and 2,4-dichlorophenol (DCP) under simulated solar light irradiation. Among them, the CU0.50 composite demonstrated the highest photocatalytic performance and reached 91.5% for TC, and 94.3% for DCP. In addition, a logical solid-state Z-type electron transfer mechanism is presented with the results of radical scavenging and ESR experiments to illustrate the intensive decomposed ability of the photocatalytic system. The enhanced photocatalytic performance of CUx heterostructures can be attributed to the formation of a band-position-matched hollow structure heterojunction between CeO2 and UIO-66-NH2, which can effectively inhibit the recombination of carriers and increase the specific surface area as well as the light absorption. Moreover, the oxidation and reduction ability of the charge carriers was also increased. This work resulted in a feasible idea for removing organic pollutants and hydrogen production by traditional inorganic semiconductor/MOF-based heterostructured photocatalysts.

Pharmacodynamics of Dracorhodin Perchlorate and Its Inflammation-Targeting Emulsion Gel for Wound Healing.

The mechanism of dracorhodin perchlorate for the repair of rat skin wounds was investigated. In order to screen a more favorable drug delivery system for wound repair, the therapeutic effect of dracorhodin perchlorate inflammation-targeted emulsion gel was compared with that of non-targeted emulsion gel on rat wounds. Compared with non-targeted emulsion gels, inflammation-targeted emulsion gels had a better transdermal penetration and lower potentials (-51.6 mV and -17.1 mV, respectively). The recovery of the wound from the dracorhodin perchlorate inflammation targeted emulsion gel group was better than that of the dracorhodin perchlorate inflammation non-targeted emulsion gel group and the positive drug group. Compared with the no-target emulsion gel group, the bFGF expression on day 7 and the EGF expression on day 14 in the targeted emulsion group showed 45.5% and 49.9% improvement, respectively. Pathological tissue slices showed that the epidermis, dermis, and basal layer inflammatory cells in the inflammation-targeted emulsion gel group and non-targeted emulsion gel group were significantly reduced, the granulation tissue proliferation was obvious, and the inflammation-targeted emulsion gel group was more effective. The results proved that dracorhodin perchlorate had a repairing effect on rat skin wounds, and its mechanism might be related to the promotion of the expression of EGF and bFGF in tissues.

Enhanced photocatalytic performance over PANI/NH2-MIL-101(Fe) with tight interfacial contact.

Constructing a suitable heterojunction structure while maintaining a tight interface to promote the separation of photogenerated electrons is of great significance for improving the photocatalytic activity. In this paper, a new PANI/NH2-MIL-101(Fe) II-scheme heterojunction was prepared by a hydrothermal method. PANI with a porous structure was firstly obtained by the template method, and then PANI fragments were loaded on the surface of NH2-MIL-101(Fe) crystals under hydrothermal conditions to obtain a PANI/NH2-MIL-101(Fe) photocatalyst. The photocatalytic degradation of TC under simulated sunlight can reach 90% within an hour, and the maximum hydrogen evolution rate is 7040 µmol g-1 h-1 under visible light. The enhanced catalytic performance of PANI/NH2-MIL-101(Fe) was attributed to the appropriate matching of the VB and CB of PANI and NH2-MIL-101(Fe), and secondly, the coordination bonds formed between PANI and NH2-MIL-101(Fe) provided a channel for charge separation and transfer. Finally, a possible mechanism of the photocatalytic system was proposed through a free radical capture experiment and characterization analysis. More importantly, the experiment proved that the heterojunction formed by PANI and NH2-MIL-101(Fe) can achieve the effect of complementing each other, which provides a feasible idea and method for the design of efficient heterojunction photocatalysts.

Synthesis of Layered Double Hydroxides with Phosphate Tailings and Its Effect on Flame Retardancy of Epoxy Resin.

In this work, phosphate tailings (PTs) were used as raw materials for the preparation of Ca-Mg-Al layered double hydroxides (LDHs-1) and Ca-Mg-Al-Fe layered double hydroxides (LDHs-2) by co-precipitation method. The as-prepared samples were characterized by FT-IR, SEM, XRD, and XPS and applied as a flame retardant to improve the fire safety of epoxy resin (EP). The results showed that both LDHs-1 and LDHs-2 exhibited layered structure and high crystallinity. Compared with neat EP, the value of limiting oxygen index (LOI) increased from 25.8 to 29.3 and 29.9 with 8 wt% content of LDHs-1 and LDHs-2, respectively. The flame retardant properties of the composite material were characterized by cone calorimeter (CC), and the results showed that the peak value of the smoke production rate (SPR) decreased more than 45% and 74%, total smoke production (TSP) reduced nearly 64% and 85% with the addition of LDHs-1 and LDHs-2. Meanwhile, the value of the total heat release (THR) reduced more than 28% and 63%. The conversion from LDHs to layered double oxide (LDO) might be conducive to the fire safety of EP. Moreover, the transformation of Fe-OH to Fe-O could promote the early cross-linking of polymer. In summary, LDHs-2 could significantly improve the carbonization process of EP and suppress the smoke released during the combustion process.

Preparation of a Novel Organic Phosphonic Acid Intercalated Phosphate Tailings Based Hydrotalcite and Its Application in Enhancing Fire Safety for Epoxy Resin.

Phosphate tailings (PTs) are solid waste, which is produced by phosphate flotation. In this work, PTs were used as raw materials for the preparation of diethylenetriamine pentamethronic acid (DTPMP) intercalated trimetal (Ca-Mg-Al) layered double hydroxides (TM-DTPMP LDHs) by co-precipitation method. TM-DTPMP LDHs were characterized by X-ray diffraction, fourier-transform infrared spectroscopy, scanning electron microscopy, differential thermal gravimetric analysis, X-ray photoelectron spectroscopy and applied as a flame retardant to improve the fire safety of epoxy resin (EP). The results showed that the composite materials exhibited obvious layered structure. After intercalation, layer spacing increased from 0.783 to 1.78 Å. When the amount of TM-DTPMP LDH in EP was 8%, the limitted oxygen index of the composite material increased from the original 19.2% to 30.2%. In addition, Cone calorimeter (CC) and Raman spectrum results indicated that with the addition of TM-DTPMP LDHs, the value of heat release rate peak (pHRR) and total heat release (THR) were reduced by more than 43% and 60%, while the value of smoke formation rate (pSPR) and the total smoke production (TSP) decreased nearly 64% and 83%, respectively. The significant reduction in the release of combustion heat and harmful smoke during EP combustion may be attributed to the synergistic flame-retardant effect between hydrotalcite and DTPMP. This work exhibited great potential for the green recycling of PTs and the enhancement of the fire safety of EP.

Green Conversion of Saponins to Diosgenin in an Alcoholysis System Catalyzed by Solid Acid Derived from Phosphorus Tailings.

This work proposed to prepare solid acid from phosphorus tailings and successfully convert Dioscorea zingiberensis C.H. Wright (DZW) into diosgenin from the perspective of solid waste resource reuse and clean production. The results showed that SiO2-SO3H solid acid could catalyze the production of diosgenin from total saponins under solvothermal reaction conditions. In addition, the parameters of a single factor, such as the amount of SiO2-SO3H, solvent volume, reaction temperature, and reaction time, were optimized to confirm the optimal range of reaction conditions, and the optimal process conditions were determined by the response surface method. The yield of diosgenin was 2.45 ± 0.17% under the optimum conditions, and the yield of diosgenin was increased by 12.90% compared with the traditional acid hydrolysis process. Except the relatively higher catalytic activity, the alcoholysis approach for the production of diosgenin has no waste liquid to discharge. The products were analyzed by high-performance liquid chromatography-mass spectrometry, and the pathway to convert total saponins into diosgenin under SiO2-SO3H has been proposed. Moreover, the adopted catalyst can be prepared with very low cost from phosphorus tailings. Considering the obvious superiorities, the alcoholysis approach in this work could be a promising strategy for green production of diosgenin as well as a possible utilization pathway of phosphorus tailings.

Water-mediated proton conduction in Ni(ii) and Co(ii) benzenetriphosphonates.

Two novel transition metal compounds, [Ni(4,4'-bipyH)2(H2O)4]·2(H4bmt)·9H2O (1) and [Co(4,4'-bipy)(H2O)4][Co(4,4'-bipyH)2(H2O)4]·2(H3bmt)·6H2O (2), have been synthesized. They possess continuous H-bond networks and high-density [PO3] groups, which give conductivity values in the order of 10-3 S cm-1 in a wide temperature range and 98% relative humidity.

Synthesis, crystal structures and magnetic properties of a series of chair-like heterometallic [Fe4Ln2] (Ln = GdIII, DyIII, HoIII, and ErIII) complexes with mixed organic ligands.

Four chair-like hexanuclear Fe-Ln complexes containing mixed organic ligands, namely, [Fe4Ln2{(py)2CO2}4(pdm)2(NO3)2(H2O)2Cl4]·xCH3CN·yH2O (Ln = GdIII (1, x = 1, y = 0), DyIII (2, x = 1, y = 1), HoIII (3, x = 0, y = 2), and ErIII (4, x = 1, y = 3); (py)2CO2H2 = the gem-diol form of di-2-pyridyl ketone and pdmH2 = 2,6-pyridinedimethanol) have been obtained by employing di-2-pyridyl ketone and 2,6-pyridinedimethanol reacting with FeCl3 and Ln(NO3)3 in MeCN. The structures of 1-4 are similar to each other except for the number of lattice solvent molecules. Four FeIII and two LnIII in these complexes comprise a chair-like core with the "body" constructed by four FeIII ions and the "end" constructed by two LnIII ions. Among the four compounds, 2 shows field-induced single molecule magnet behavior as revealed by ac magnetic susceptibility studies, with the effective energy barrier and the pre-exponential factor of 22.07 K and 8.44 × 10-7 s, respectively. Ab initio calculations indicated that, among 2_Dy, 3_Ho and 4_Er fragments, the energy gap between the lowest two spin-orbit states for 2_Dy is the largest, while the tunneling gap for 2 is the smallest. These might be the reasons for complex 2 exhibiting SMM behavior. Additionally, the orientations of the magnetic anisotropy of DyIII in 2 were obtained by electrostatic calculations and ab initio calculations, both indicating that the directions of the main magnetic axis of Dy1 ions are almost aligned along Dy1-O5 (O5 from the pdm2- ligand).

Regulation of magnetic relaxation behavior by replacing 3d transition metal ions in [M2Dy2] complexes containing two different organic chelating ligands.

Four tetranuclear 3d-4f complexes, namely [Fe2Ln2(L)2(teaH)2(Cl)2](NO3)2·4CH3CN (H2L = N1,N3-bis(3-methoxysalicylidene)diethylenetriamine, teaH3 = triethanolamine, Ln = Dy for 1 and Ln = Gd for 1') and [Co2Ln2(L)2(pdm)2(CH3COO)2(CH3OH)2](NO3)2·xCH3OH·yH2O (pdmH2 = 2,6-pyridinedimethanol, Ln = Dy, x = 5 and y = 2.5 for 2 and Ln = Gd, x = 6 and y = 1.5 for 2'), have been reported. Two FeIII and two DyIII in 1 formed a zigzag Fe1-Dy1-Dy1a-Fe1a arrangement with a Fe1-Dy1-Dy1a angle of 105.328(3)°. However, in contrast to 1, two CoIII and two DyIII ions in 2 formed a more linear Co1-Dy1-Dy1a-Co1a arrangement with a Co1-Dy1-Dy1a angle of 141.86(2)°. Additionally, two DyIII ions in 1 are eight-coordinated with a triangular dodecahedron geometry, while two DyIII ions in 2 adopt nine-coordination with a muffin geometry. Magnetic studies revealed slow magnetic relaxation behavior for 1, with an energy barrier Ea of 6.9 K. For 2, single molecule magnet behavior was presented under a zero dc field with an effective energy barrier Ueff of 64.0(9) K. Ab initio calculations for 1 and 2 indicate that compared to 2, complex 1 has a larger transversal magnetic moment of its ground Kramers doublets (KD) and a larger value of the tunnelling parameter (Δt) for the exchanged coupled ground state, which may result in poor single molecule magnet behavior for 1.

A water stable layered Tb(iii) polycarboxylate with high proton conductivity over 10-2 S cm-1 in a wide temperature range.

An unprecedented Tb(iii) polycarboxylate, {[Tb4(TTHA)2(H2O)4]·7H2O}n (1), has been synthesized. It possesses an efficient proton transfer pathway formed by water molecules and carboxyl groups, which exhibits proton conductivity over 10-2 S cm-1 at 295-358 K and 98% relative humidity.

Metal organic frameworks-assisted fabrication of CuO/Cu2O for enhanced selective catalytic reduction of NOx by NH3 at low temperatures.

Porous CuO/Cu2O heterostructure was successfully synthesized through a metal organic frameworks (MOFs)-assisted template method. Tunable production of pure phase CuO and Cu2O could be achieved by regulating the coordination environment of copper. The copper oxides inherited the polyhedral morphology from the Cu MOFs and possessed higher surface area and larger pore volume. Compared with pure CuO and Cu2O, heterostructured CuO/Cu2O displayed remarkably enhanced NH3-SCR de-NOx activity and N2 selectivity in a low temperature range of 170-220 °C. Systematical in situ DRIFT characterization revealed that the NH3-SCR of NOx over CuO/Cu2O heterostructure followed Eley-Rideal (E-R) mechanism, which was greatly improved by the abundant Lewis acid sites, improved O2 adsorption and the synergistic effect between Cu+ and Cu2+. In addition, CuO/Cu2O heterostructure exhibited excellent H2O, SO2, alkali metals, and hydrocarbon durability, indicating its potential use in industrial NH3-SCR of NOx.

Preparation of magnetic polyimide@ Mg-Fe layered double hydroxides core-shell composite for effective removal of various organic contaminants from aqueous solution.

In this work, a novel core-shell structured magnetic polyimide@layered double oxides (LDO) composites coating a porous polyimide (PI)-coated Fe3O4 magnetic core and layered double hydroxide (LDH) has been successfully synthesized by solve-thermal synthesis and co-precipitation process. The magnetic PI@LDO composites were characterized by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), thermogravimetry analysis (TGA) and magnetic properties analysis. The composite materials displayed core-shell structure with flower-like morphology. The magnetic PI@LDO composites were applied to remove tetracycline (TC), 2,4-dichlorophenol (2,4-DCP) and glyphosate (GP) from aqueous solution. The action pH value was ranged from 5 to 9 for TC and GP and 3 to 7 for 2,4-DCP, respectively. Cl- showed a weak competitive adsorption effect to TC, 2, 4-DCP and GP. In addition, the presence of humic acid (HA) could slightly reduce the adsorption capacity of magnetic PI@LDO composites. The adsorption process could be well described by pseudo-second-order model for TC and GP, while pseudo-first-order model for 2,4-DCP. The experimental data of TC and 2,4-DCP could be fitted better with Freundlich model, while that of GP were fitted better with Langmuir model. The adsorptions of TC, 2,4-DCP and GP were both spontaneous and endothermic. The adsorption capacity decreased slightly after adsorption-desorption cycles repeated five times. This study demonstrated that magnetic PI@LDO exhibited great potential to be a mild and cost-effective adsorbent for the removal of various organic contaminants from wastewater.

Single molecule magnet behaviors of Zn4Ln2 (Ln = DyIII, TbIII) complexes with multidentate organic ligands formed by absorption of CO2 in air through in situ reactions.

In this work, we report the syntheses, crystal structures and magnetic properties of three novel Zn-Ln mixed metal complexes, namely [Zn4Dy2(L1)2(L2)2(N3)2]Cl2·2H2O (1), [Zn4Tb2(L1)2(L2)2(Cl)2][ZnN3Cl3]·2H2O (2), and [Zn4Gd2(L1)2(L2)2(Cl)2][ZnN3Cl3]·2H2O (3), in which L12- and L23- were formed from the ligand L [L = N1,N3-bis(3-methoxysalicylidene)diethylenetriamine] through in situ reactions. Interestingly, carbon dioxide in air was absorbed in the process of forming carbamate ligand L23-; this can be ascribed to the insertion of CO2 into M-N amide bonds. Moreover, 1 and 2 represent the first series of 3d-4f SMMs containing carbamate ligands by fixation of CO2 in air. Single-crystal X-ray diffraction analyses reveal that the crystal structures of 1 and 2 are anion-dependent, i.e., the apical positions of the two ZnII ions in 1 and 2 are occupied by an N atom of N3- and by Cl-, respectively. However, the topologies of 2 and 3 are similar. Two ZnII ions and one LnIII (Ln = Dy (1), Tb (2) and Gd (3)) form nearly linear trinuclear [Zn2Ln] units which are double-bridged by two L23- ligands. Magnetic studies reveal that two complexes show single molecule magnet behavior under a direct current (dc) field, with effective energy barriers (Ueff) of 30.66(5) K for 1 and 8.87(3) K for 2. Ab initio calculations reveal that the DyIII ions in 1 and the TbIII ions in 2 are axial in nature; however, a difference in the tunnel splitting of 1 and 2 leads to variation in the magnetization blockades of the two complexes. Theoretical calculations also indicate that the directions of the main magnetic axes severely deviate from the coordination atoms of the first spheres of DyIII and TbIII in 1 and 2; thus further results in poor SMM behavior of the two complexes.

Two novel organic phosphorous-based MOFs: synthesis, characterization and photocatalytic properties.

Two novel metal-organic framework (MOF) photocatalysts with different structures [(Cu(H2L)(4,4'-bipy)0.5(H2O)] (1) and [Co(C14H14O6.5P2)(4,4'-bipy)0.5(H2O)2]·H2O (2) were synthesized using a hydrothermal method using a phosphonate ligand [H4L = 1,1'-biphenylene-4,4'-bis(methylene)-bis(phosphonic acid)] and 4,4'-bipyridine ligand. All the samples were characterized by elemental analysis, thermal analysis, and single crystal X-ray diffraction. As novel porous materials, the two complexes showed active performance for the reduction of Cr(vi) to Cr(iii) and the photodegradation of methylene blue (MB) dye in aqueous solution under UV light. Control experiments showed that the pH value was vital for Cr(vi) reduction, meanwhile, the use of a hole scavenger of methanol promoted the photocatalytic reduction significantly. It was also demonstrated that complexes 1 and 2 were efficient for the degradation of MB. Moreover, the possible reaction mechanism of the reaction was also investigated in detail. Finally, the cyclic experiments indicated the two photocatalysts were stable and reusable, enabling them to be potential candidates for use in environment governance.

Two pure MOF-photocatalysts readily prepared for the degradation of methylene blue dye under visible light.

Two 3D metal-organic frameworks (MOFs) with different structures, [Cu(4,4'-bipy)Cl]n (1) and [Co(4,4'-bipy)·(HCOO)2]n (2), were synthesized by means of a hydrothermal method using a typical ligand (4,4'-bipyridine), and characterized by elemental analyses, thermal analyses and single crystal X-ray diffraction. As MOF materials, the two complexes showed active performance for the photodegradation of methylene blue (MB) dye under visible light. MB degradation over the two MOF-based photocatalysts follows first-order kinetics. The addition of an H2O2 electron acceptor can markedly enhance the photocatalytic MB degradation performance via a ligand-to-metal charge transfer mechanism, especially in complex 1. Complex 1 is better than complex 2 in MB photodegradation performance under the same conditions. Moreover, complex 1 showed a stable activity for MB degradation after four consecutive usages. Owing to the advantages of the visible light response, stable structure, low cost and high yield, these MOF-based photocatalysts will facilitate new efforts in environmental purification.

Pyridine-ring containing twisttetraazaacene: Synthesis, physical properties, crystal structure and picric acid sensing.

Novel pyridine-ring containing twisttetraazaacene 9,14-diphenylpyreno[4,5-g]isoquinoline (1) and its full-carbon derivative 9,14-diphenyldibenzo[de,qr]tetracene (2) have been synthesized and fully characterized. Studies showed that compound 1 could identify picric acid (PA) over other common nitro compounds with high selectivity and sensitivity. Upon the addition of PA, the emission peak of compound 1 in CH3CN was red shifted from 447 to 555nm with a fluorescence quenching efficiency as high as 95%, the detection limit was calculated to be 2.42µM, while its full-carbon derivative (2) could not exhibit this kind of performance. The possible mechanism with the enhanced PA detection efficiency in pyridine-ring containing twisttetraazaacene (1) than its full-carbon derivative (2) was also investigated.