Self-Assembly Method for Synthesizing High-Dimensional EMOFs with High Stability and Laser Response.

Dimension and solvent molecules affect the performance of energetic metal-organic frameworks (EMOFs). High-dimensional EMOFs are usually characterized by high stability and low sensitivity due to their complex network structure. However, solvent molecules affect the detonation performance of EMOFs, and these molecules may be removed at low temperatures, resulting in structural collapse and affecting the stability of EMOFs. In this work, zero-dimensional (0D) Co(AFTO)2·(H2O)2 (EMOF 1) and Ni(AFTO)2·(H2O)2 (EMOF 2) with coordinated water molecules and [Co(AFTO)2]n·EtOH (EMOF 3) and [Ni(AFTO)2]n (EMOF 4) (AFTO = 5-(4-amino-furazan-3-yl)-1-hydroxytetrazole) with high-dimensional structure were synthesized using hydrothermal and self-assembly methods in ethanol, respectively. Structural and performance tests show that EMOF 3 and 4 exhibit remarkable thermal stability and low mechanical sensitivity. This method is a simple, effective, and green technique for synthesizing high-dimensional EMOFs with high stability through self-assembly in ethanol solution. In addition, EMOF 3 and 4 can be used as primary green laser explosives.

Spiral gas-solid two-phase flow continuous mechanochemical synthesis of salophen complexes and catalytic thermal decomposition of ammonium perchlorate.

Although mechanochemistry is increasingly becoming an alternative to traditional chemical synthesis, highly efficient continuous mechanochemical synthesis techniques are still rare. In this work, a novel spiral gas-solid two-phase flow (S-GSF) synthesis technique for the mechanochemical synthesis of salophen complexes has been reported, which is an approach for continuous synthesis based solely on airflow impacting the reaction. The synthesis of salophen-Br-Cu was used as a model reaction to optimize the reaction conditions, and three other salophen complexes, namely, salophen-Br-Co, salophen-Br-Ni, and salophen-Br-Zn were synthesized on this basis. The structure and thermal stability of the obtained products were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, UV-vis spectroscopy, nuclear magnetic resonance spectroscopy, scanning electron microscopy, and differential thermal analysis (DTA). The results showed that these complexes can be obtained continuously at a rate close to 4 g min-1, and the corresponding space-time yield is close to 1.2 × 105 kg m-3 day-1. In addition, DTA was used to analyze the catalytic performance of the complex for ammonium perchlorate (AP). The results showed that compared to the conditions for pure AP, salophen-Br-Co and salophen-Br-Cu could significantly reduce the high-temperature decomposition of AP pyrolysis to 77.0 and 102.1 °C, respectively. According to the method of Kissinger calculations, the Ea of AP decomposition decreased from 217.3 kJ mol-1 to 131.0 and 118.5 kJ mol-1, respectively. The TG data at different heating rates were analyzed using two isoconversion methods, i.e. Flynne-Walle-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS). The activation energies of AP, AP + 10 wt% salophen-Br-Co, and AP + 10 wt% salophen-Br-Cu were calculated. When the conversion degree (α) is between 0.1 and 0.9, the Ea values obtained from the two isoconversion methods are similar and exhibit certain matching. These two isoconversion methods also confirm Kissinger's calculations.

Gelatin-modified Mxene carbon aerogels for ammonium-perchlorate-catalyzed thermal decomposition.

The assembly of 2D Ti3C2Tx nanosheets into 3D structures with orderable structure has great importance for their use as catalyst carriers. However, Ti3C2Tx nanosheets are prone to accumulate in aqueous solutions owing to the strong van der Waals forces between Ti3C2Tx nanosheet layers, degrading their chemical properties. Carbon aerogel (Ti3C2Tx/G/Co) with a 3D porous structure and cobalt as the active site was prepared by a simple co-assembly-freeze-drying-high-temperature carbonization method for application in catalysis of ammonium perchlorate.

C60-CN: A bifunctional interface modification material for perovskite solar cells.

Titanium dioxide (TiO2) is regularly used as an electron transport material in n-i-p perovskite solar cells (PSCs). However, massive defects exist on the TiO2 surface, which will lead to serious hysteresis and interface charge recombination of the device, thus affecting the device's efficiency. In this study, a cyano fullerene pyrrolidine derivative (C60-CN) was synthesized and applied to PSCs for the first time to modify the TiO2 electron transport layer. Systematic studies have shown that the addition of the C60-CN modification layer on the TiO2 surface will enlargement the perovskite grain size, improve the perovskite film quality, enhance electron transport, and reduce charge recombination. The C60-CN layer can significantly reduce the density of trap states in the perovskite solar cells. As a result, the PSCs based on C60-CN/TiO2 obtained a power conversion efficiency (PCE) of 18.60%, suppressing the hysteresis and improving the stability, whereas the PCE of the control device using the original TiO2 ETL was lower, 17.19%.

Concise synthesis of low-cost fullerene derivatives as electron transport materials for efficient air-processed invert perovskite solar cells.

Due to its excellent charge extraction ability, fullerene derivative phenyl-C61-butyric acid methyl ester (PCBM) is widely used as electron transport materials (ETM) in invert perovskite solar cells. However, the complicated synthetic routes and low productivity of PCBM limiting its commercial application. Moreover, the insufficient defect passivation ability of PCBM is contributed to inferior device performance because it lacks hetero-atoms/groups with lone pair electrons, it is highly desirable for exploration of new fullerene-based ETM with excellent photoelectric properties. Therefore, three new fullerene malonate derivatives were synthesized by simple two-step reaction with a high yield, and then developed as electron transport materials in invert perovskite solar cells which fabricated in air condition. The constituent thiophene and pyridyl group of the fullerene-based ETM can heighten the chemical interaction between under-coordinated Pb2+ and lone pair electrons of N, S atom by electrostatic interaction. Hence, the air-processed unencapsulated device with new fullerene-based electron transport materials (C60-bis(pyridin-2-ylmethyl) malonate (C60-PMME)) can obtain a enhanced power conversion efficiency (PCE) of 18.38%, which is significantly higher than the PCBM-based devices (16.64%). Additionally, the C60-PMME-based devices exhibit significantly more outstanding long-term stability than PCBM-based devices, owing to the strong hydrophobic properties of these new fullerene-based ETM. This study shows the promising potentials of these new low-cost fullerene derivatives as ETM to replace commercially used fullerene derivatives PCBM.

Synthesis and Characterization of Random Block Hydroxyl-Terminated Polyfluoroether-Based Polyurethane Elastomers with Fluorine-Containing Side Chains.

Polype ntafluoropropane glycidyl ether (PPFEE), a new random block hydroxyl-terminated polyfluoroether, was synthesized successfully by cationic ring-opening polymerization of 2-(2,2,3,3,3-pentafluoropropoxymethyl) oxirane, and its molecular structure was confirmed by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectrometry, and gel permeation chromatography. The PPFEE-based polyurethane elastomers featuring fluorine in their side chains were prepared using PPFEE as soft segments, polyisocyanate polyaryl polymethylene isocyanate as hard segments, and dibutyltin dilaurate as catalysts under different curing conditions. The microphase separation, mechanical performance, and thermal behavior of the elastomers were investigated by differential scanning calorimetry, uniaxial tensile test, and thermal gravimetric analysis, respectively. Based on the results, the percentage of hard segments dissolved into the soft segments of elastomers was opposite to the change in breaking strength. The PPFEE-based polyurethane elastomer cured with 20 wt% PAPI at the curing temperature of 50 °C displayed the maximum tensile elongation of 2.26 MPa with an elongation at break of nearly 150%. The increased contents of PAPI can effectively strengthen the tensile strength, and the maximum tensile elongation was 3.04 MPa with an elongation at break of nearly 90% when the content of PAPI was 26 wt%. In addition, the PPFEE-based polyurethane elastomers exhibited excellent resistance to thermal decomposition and a sharp weight loss temperature at around 371 °C. All the results demonstrated that the PPFEE may be a potential polymeric binder as one of the ingredients applied to future propellant formulations.

Gas-solid two-phase flow method for preparing trimesic acid series MOFs for catalytic thermal decomposition of ammonium perchlorate.

The Zn-BTC, Co-BTC and Zn-Co-BTC series metal-organic frameworks were successfully prepared by a gas-solid two-phase flow (GSF) method with zinc nitrate, cobalt nitrate, and 1,3,5-benzenetricarboxylic acid (H3BTC) as raw materials. Single-crystal structures were obtained by the solvothermal method, and the structure and thermal stability of the target materials were characterized by FT-IR, XRD, SEM, energy-dispersive X-ray spectroscopy and DTA. The three obtained target substances were applied to catalyze the thermal decomposition of ammonium perchlorate (AP), and the performance was longitudinally compared. Testing and calculation results showed that when 10 wt% of the sample was added, monometallic Zn-BTC and Co-BTC lowered the AP pyrolysis temperature by 64.1 °C and 92.3 °C, respectively, and their activation energies decreased from 215.96 kJ mol-1 to 136.27 kJ mol-1 and 125.29 kJ mol-1, respectively. Bimetallic Zn-Co-BTC lowered the AP pyrolysis peak by 103.1 °C and the activation energy to 115.56 kJ mol-1, indicating that the series of samples exhibited good catalytic performance, and the catalytic effect of the bimetallic sample was significantly better than those of the monometallic samples.

Synthesis of CuII and CdII Metal-Organic Frameworks Based on 4,5-Bis(1-hydroxytetrazol-5-yl)-1,2,3-triazole and Their Effects as the Catalyst in Ammonium Perchlorate Thermal Decomposition.

Two new three-dimensional (3D) energetic metal-organic frameworks (EMOFs), namely, [Cu(OBTT)(NC2H8)2]n (1) and [Cd3(OBTT)2(H2O)2]n·4H2O (2), where H3OBTT = 4,5-bis(1-hydroxytetrazol-5-yl)-1,2,3-triazole, were prepared, and their structures were characterized by single-crystal X-ray diffraction analysis, which revealed that the EMOFs feature a rigid 3D framework architecture. The possibility of these two EMOFs as potential catalysts for the thermal decomposition of ammonium perchlorate (AP) was investigated. The results show that they have significant catalytic activity, up to reducing the peak temperature of AP decomposition from 704.0 to 613.6 K and contracting the decomposition temperature range from 451 to 320 K, which is almost one-third less than the decomposition temperature range of pure AP. The Kissinger and Ozawa-Doyle methods were used to calculate the kinetic parameters of the thermal decomposition of pure and mixed AP samples. The experimental results suggest that compound 1 has potential applications in the field of explosives and propellants. All properties suggest that compound 1 can be used as a potential catalyst.

Controllable Structural Modulation: Assembling Variable Dimension Energetic Metal-Organic Frameworks via Free Protons.

Herein, we provide an efficient strategy for constructing three-dimensional (3D) energetic coordination polymers (ECPs), namely, metal-organic frameworks (EMOFs), avoiding solvent coordination without changing the organic ligands or metal nodes. Three ECPs with the same ligand and metal center, namely, two-dimensional (2D) layer ECP [Pb(HOBTT)(H2O)2]n (1), 3D solvent-free EMOFs [Pb(HOBTT)]n (2), and dense [Pb3(OBTT)2]n (3) (H3OBTT = 4,5-bis(1-hydroxytetrazol-5-yl)-2H-1,2,3-triazole), were rationally designed and synthesized via free protons. As expected, the theoretical density of 3 (4.080 g·cm-3) is greater than those of 2 (3.299 g·cm-3) and 1 (3.055 g·cm-3). Thermal stabilities indicate that their decomposition temperature exceeds 300 °C. Theoretical calculations show that the detonation performance of 3 is better than that of 1 and 2. The detonation performance of 1-3 was further proven by laser irradiation.

Preparation of a Chitosan-Lead Composite Carbon Aerogel and Its Catalytic Thermal Decomposition Performance on Ammonium Perchlorate.

Chitosan-lead (CS-Pb) carbon aerogels were prepared by ionic cross-linking and high-temperature carbonization using chitosan (CS) as the carbon precursor. The obtained carbon aerogels were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), and X-ray photoelectron spectroscopy (XPS). The obtained aerogels have a 3D structure and a large surface area, which can effectively prevent the agglomeration phenomenon of metals. Differential thermal analysis (DTA) was used to analyze the catalytic performance of a carbon aerogel for ammonium perchlorate (AP). The results showed that the CS-Pb carbon aerogel reduced the peak temperature of AP pyrolysis from 703.9 to 627.7 K. According to the Kissinger method calculations, the Ea of AP decomposition decreased about 27.2 kJ/mol. The TG data at different warming rates were analyzed by the Flynne-Walle-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods, which are two of the isoconversion methods, and the activation energies of AP and AP+CS-Pb-3.5 were calculated. Between the conversion degrees (α) of 0.1 and 0.9, the Ea values obtained by the two isoconversion methods are similar and have a certain match. Also, the two isoconversion methods confirm Kissinger's calculation. Finally, thermogravimetry-mass spectrometry (TG-MS) was used to monitor the gases generated during the thermal decomposition of the AP+CS-Pb-3.5 system in real time.

Gas-solid phase flow synthesis of Cu-Co-1,3,5-benzenetricarboxylate for electrocatalytic oxygen evolution.

Using an environmentally friendly method to produce a stable and highly catalytically active electrocatalyst for the oxygen evolution reaction (OER) is becoming increasingly urgent. Herein, a novel bimetallic metal-organic framework (MOF), specifically a copper-cobalt 1, 3, 5-benzenetricarboxylate (Cu-Co-BTC) MOF, was successfully prepared by employing the gas-solid two-phase flow (GSF) synthetic technique. The as-prepared Cu-Co-BTC with its multiple active sites afforded a current density of 10 mA cm-2 at 239 mV for the OER in a 1 mol L-1 KOH solution, and showed a better electrocatalytic performance than did single-metal-containing Cu-BTC and Co-BTC materials. This work provides a new idea, one involving using novel gas-solid phase reactions for the preparation of electrocatalysts in large quantities.

Zeolite Imidazolate Frameworks-67 Precursor to Fabricate a Highly Active Cobalt-Embedded N-Doped Porous Graphitized Carbon Catalyst for the Thermal Decomposition of Ammonium Perchlorate.

The more apparent specific heat release at a lower high-temperature decomposition (HTD) temperature of ammonium perchlorate (AP) poses a challenge for the development of highly active catalysts. In this work, a well-designed cobalt-embedded N-doped porous graphitized carbon (Co@NC) catalyst is obtained by high-temperature calcination of a zeolite imidazolate frameworks-67 precursor, in which the cobalt catalytic active center realizes effective nanoscale dispersion; meanwhile, the cobalt and N-doped porous graphitized carbon can release considerable heat after oxidation, and the cobalt oxides have an excellent catalytic effect on reducing the HTD temperature of AP. The catalytic activity of Co@NC was tested by a differential thermal analytical method. The results indicated that the HTD peak of AP was significantly decreased by 100.5 °C, the apparent activation energy of the HTD reaction of AP was reduced by 82.0 kJ mol-1, and the heat release compared with pure AP increased 2.9 times. On teh basis of these findings, Co@NC is expected to be one of the best candidate materials for AP thermal decomposition.

Fabrication and photocatalytic activity of graphitic-C3N4 quantum dots-decorated basic zinc carbonate prepared by a co-precipitation method.

Graphitic carbon nitride quantum dots (CNQDs) with a high quantum yield (up to 43%) were synthesized by incorporating the unique organic functional group of barbituric acid into the framework of the carbon nitride structure by supramolecular pre-organization. The CNQDs were introduced onto the surface of basic zinc carbonate (BZC) by co-precipitation. The resulting CNQDs/BZC composite showed that the degradation efficiency of tetracycline was 2.4 times higher than that of ZnO. The Z-scheme mechanism for the as-prepared sample was proposed for the enhanced photocatalytic degradation rate. The ˙O2- and ˙OH radicals played major roles due to the suitable bandgap. Finally, the formation and possible photocatalytic mechanisms of the CNQDs/BZC composite are proposed.

Series of AzTO-Based Energetic Materials: Effect of Different π-π Stacking Modes on Their Thermal Stability and Sensitivity.

π-Stacking is common in materials, but different π-π stacking modes remarkably affect the properties and performances of materials. In particular, weak interactions, π-stacking and hydrogen bonding, often have a great impact on the stability and sensitivity of high-energetic compounds. Therefore, several of energetic materials based on 1,1'-dihydroxyazotetrazole (1) with a nearly flat structure, such as the salts of aminoguanidine (2), 1,3-diaminoguanidine (3), imidazole (4), pyrazole (5) and triaminoguanidine (6), and a cocrystal of 2-methylimidazole (7), were designed and synthesized. Based on single-crystal diffraction data, thermal decomposition behaviors, and the mechanical sensitivity test, the compounds of 4, 5, and 7 with face-to-face π-π stacking display outstanding thermal stability and insensitivity.

Design and synthesis of N-hydroxyalkyl substituted deferiprone: a kind of iron chelating agents for Parkinson's disease chelation therapy strategy.

The blood-brain barrier (BBB) permeability of molecules needs to meet stringent requirements of Lipinski's rule, which pose a difficulty for the rational design of efficient chelating agents for Parkinson's disease chelation therapy. Therefore, the iron chelators employed N-aliphatic alcohols modification of deferiprone were reasonably designed in this work. The chelators not only meet Lipinski's rule for BBB permeability, but also ensure the iron affinity. The results of solution thermodynamics demonstrated that the pFe3+ value of N-hydroxyalkyl substituted deferiprone is between 19.20 and 19.36, which is comparable to that of clinical deferiprone. The results of 2,2-diphenyl-1-picrylhydrazyl radical scavenging assays indicated that the N-hydroxyalkyl substituted deferiprone also possesses similar radical scavenging ability in comparison to deferiprone. Meanwhile, the Cell Counting Kit-8 assays of neuron-like rat pheochromocytoma cell-line demonstrated that the N-hydroxyalkyl substituted deferiprone exhibits extremely low cytotoxicity and excellent H2O2-induced oxidative stress protection effect. These results indicated that N-hydroxyalkyl substituted deferiprone has potential application prospects as chelating agents for Parkinson's disease chelation therapy strategy.

Tailored conductive fullerenes-based passivator for efficient and stable inverted perovskite solar cells.

Interfacial defects result in a limitation to the development of highly efficient and stable perovskite solar cells. The passivation of these defects by adopting various interfacial defects passivation agents is a common method for boosting device performance. However, most existing interfacial defects passivation agents form poorly conductive aggregates at the perovskite interface with the electron transport layer (ETL), hindering the transport of charge carriers. In addition, the electron mobility of passivation agents is an important factor that affects the electron communication between the adjacent layers. Herein, a fullerene-based molecular passivator, [60]fullerene-4-(1-(4-(tert-butyl)phenyl)pyrrolidin-2-yl)benzenaminium (C60-tBu-I), is designed and synthesized. This novel n-doping fullerene ammonium iodide is developed as an interfacial modification agent to accelerate charge transport from the perovskite active layer into the ETL while hindering the nonradiative charge carrier recombination. Hence, compared with the control devices (15.66%), C60-tBu-I-modified device presents a higher efficiency of 17.75%. More importantly, the tert-butyl group dramatically enhances the resistance of perovskite films to water molecular. As a result, C60-tBu-I-modified devices exhibit excellent long-term stability, remaining at more than 87% of the initial power conversion efficiency value after storage for 500 h.

Fabrication of recyclable reduced graphene oxide/graphitic carbon nitride quantum dot aerogel hybrids with enhanced photocatalytic activity.

Recyclable photocatalysts that can efficiently respond to visible light must be developed for practical application. Herein, three-dimensional (3D) reduced graphene oxide (rGO)/graphitic carbon nitride quantum dot (CNQD) aerogel hybrids for harvesting visible light were synthesized via a hydrothermal method. The graphitic CNQDs were not only decorated on but also integrated onto the surface of rGO. The CNQDs produced photogenerated charge under visible light. 3D rGO could serve as an acceptor of the photogenerated electrons and stereoscopically facilitated the charge transfer through aerogel networks owing to its high conductivity. The ciprofloxacin removal ratio of the aerogel hybrids was about 6.1 times higher than that of bulk g-C3N4.

New Core-Shell Hybrid Material IR-MOF3@COF-LZU1 for Highly Efficient Visible-Light Photocatalyst Degrading Nitroaromatic Explosives.

Nitroaromatic explosives in wastewater are hardly degraded, which seriously endangers the ecological environment and human safety. We report a core-shell structure hybrid material (IR-MOF3@COF-LZU1) with high crystallinity and graded porosity. It is an effective visible-light-driven photocatalyst that degrades p-nitrophenol (PNP). After 3.5 h, PNP was degraded well under visible light, and it is proven that the photocatalytic degradation is efficient. In addition, this photocatalytic activity adhered to pseudo-first-order kinetics, and a possible photocatalytic mechanism was discussed in detail.

Engineering of Electron Extraction and Defect Passivation via Anion-Doped Conductive Fullerene Derivatives as Interlayers for Efficient Invert Perovskite Solar Cells.

The major limitation of organic-inorganic perovskite solar cell performance is the existence of numerous charged defects at the absorption layer surface, which caused the charge carrier to recombine depravation. These defects have a remarkable influence on charge extraction, which further caused the instability of the device and induced severe hysteresis. Here, three low-cost anion-doped conductive fullerene derivatives, fullerene bis(phenethyl alcohol) malonate (FMPE-I), fullerene bis(ethylenediamine) malonamide (FEDA-I), and fullerene bis(propanediamine) malonamide (FPDA-I), are developed for the first time as interfacial layers between perovskite and phenyl-C61-butyric acid methyl ester (PCBM) in planar invert perovskite solar cells by mild solution fabrication. The constituent Lewis basic halides and the specific amide groups of conductive fullerene derivatives efficaciously heighten the chemical interaction between perovskite and conductive fullerene derivatives since the iodide can combine with undercoordinated Pb2+ by electrostatic interaction and the amide group can facilely be combined with I by hydrogen bonding, improving the dual passivation of perovskite defects. Moreover, due to the well-matched energy level of conductive fullerene derivatives and the high conductivity of the perovskite/interlayer film, the electron extraction capacity can be effectively enhanced. Consequently, superior optoelectronic properties are achieved with an improved power conversion efficiency of 17.63%, which is considerably higher than that of the bare PCBM-based devices (14.96%), for the perovskite device with conductive interlayer treatment along with negligible hysteresis. Moreover, hydrophobic conductive fullerene derivatives improve the resistance of the device to moisture. The conductive fullerene derivative-based devices without encapsulation are maintained at 85% of the pristine power conversion efficiency value after storage under ambient conditions (25 °C temperature, 60% humidity) for 500 h.

Novel energetic metal-organic frameworks assembled from the energetic combination of furazan and tetrazole.

Two novel 2D energetic metal-organic frameworks (MOFs), namely, [Pb(BTF)(H2O)2]n (1) and [Ba(BTF)(H2O)4]n (2), that possess the combined advantages of tetrazole and furazan rings were successfully synthesized. Their crystal structures were determined by single-crystal X-ray diffraction and fully characterized by elemental analysis and FT-IR spectroscopy. Their thermal stability and sensitivity were also investigated. The MOFs have good thermal stability (Tdec > 250 °C) and are insensitive to impact (IS > 25 J) and friction (FS > 360 N), and also have good oxygen balance (Ω > -20%). Crystal structure analyses reveal that the two compounds have densities up to 3.382 g cm-3 and 2.336 g cm-3, respectively, and excellent physicochemical properties. Tetrazole and furazan rings as ligands can commendably increase the densities and oxygen balance of energetic MOFs, thereby enhancing their detonation performance. We anticipate that this work will open a new direction for the development of energetic MOFs. Moreover, (1) exhibits outstanding catalytic performance for ammonium perchlorate (AP). When the supramolecular complex was added in 10 wt% amount, the high-temperature decomposition peak of AP advanced by 95 °C and the reaction rates enhanced by lowering the activation energy.