•UiO-66 crystals were prepared in a two step modulated synthesis.•UiO-66 with various morphologies and enhanced porous structures were derived.•Enhanced DCM adsorption capabilities were obtained by the modulating process.•The samples remained crystalline structures after dichloromethane adsorption.UiO-66 compounds with various morphologies and enhanced porous structures were prepared by controlling the acetic acid modulator amounts in a two step synthesis process. Influences of the modulation on morphologies and structures are demonstrated with the aid of SEM, PXRD, N2 sorption and TGA characterizations. Vapor adsorption experiments show the dichloromethane adsorption capabilities were greatly enhanced by the modulating process and a maximum dichloromethane uptake of 510.3 mg/g was obtained. These effects can be attributed to the “missing-linker defect” introduced by acetic acid. Besides, the materials remained their crystalline structures after dichloromethane sorption, indicating their potential use in air purification as an attractive adsorbent.Download high-res image (276KB)Download full-size image

•A facile synthesis method of Al-fumarate MOF nano-flakes is proposed.•The Al-fumarate compound has a large surface area and high thermal stability.•The nanomaterial has good VOCs adsorption performance.•The nano-flakes have high dichloromethane/trichloromethane adsorption selectivity.In this letter, Al-fumarate metal–organic framework (MOF) nano-flakes were synthesized and volatile organic compounds adsorption performance of this nanomaterial was investigated. The adsorption equilibria results indicated that dichloromethane (DCM) was preferentially adsorbed over trichloromethane (TCM). Moreover, we used ideal-adsorbed solution theory (IAST) method to predict the binary adsorption selectivity performance. It showed a high adsorption selectivity molar ratio about 20.0 towards an equimolar mixture of DCM/TCM vapors at 298 K on this solid, which was much higher than that of HKUST-1 and IRMOF-3 (2.17 and 5.62, respectively). This study indicates the potential use of Al-fumarate nano-flakes in volatile organic compounds (VOCs) recovery by selective adsorption.

The photoluminescence (PL) properties of inorganic–organic perovskites can be drastically changed by tuning the halogen composition, especially the Cl content. However, our research demonstrated that in addition to the influence of Cl concentration, the PL emission intensity of CH3NH3PbBr3 strongly depends on the content of CH3NH3Br in the coating solution. The effects of CH3NH3Br and Cl concentrations on the PL properties of CH3NH3PbBr3–xClx were investigated. We found that a strong PL emission intensity of CH3NH3PbBr3 can be obtained from solutions with a high CH3NH3Br concentration. The PL emission intensities of CH3NH3PbBr3–xClx films were enhanced by adjusting the molar ratio of PbBr to PbCl2 only in a highly concentrated CH3NH3Br environment. Moreover, it was found that an optimum CH3NH3Br/PbBr2/PbCl2 ratio in the precursor solutions can be used to obtain the strongest PL emission intensity of CH3NH3PbBr3–xClx films. Further studies revealed that both CH3NH3Br and Cl concentrations significantly influence the CH3NH3PbBr3–xClx films evolution, which affects their PL properties.

Zinc-based metal organic framework MOF-5, and its amino-functionalized form IRMOF-3 were successfully synthesized, characterized, and evaluated for the adsorption and separation of dichloromethane (DCM) and trichloromethane (TCM). Adsorption equilibria and kinetics of DCM and TCM on the two samples were measured at 298 K, 308 K, and 318 K. In spite of the reduced porosity of IRMOF-3, the adsorption capacities of DCM and TCM were improved up to 24.5% and 27.4% when compared with MOF-5. Therefore, the additional amino group in the MOF imparts extra adsorption capability on the MOF. The binary adsorption selectivity and diffusion selectivity of DCM and TCM were predicted via the Ideal Adsorbed Solution Theory (IAST) method. The adsorption selectivity and diffusion selectivity of DCM/TCM on the IRMOF-3 were about 5.62 and 3.88 at 298 K and 2.8 kPa, which were higher than those of MOF-5. The improved adsorption capacity and enhanced adsorption selectivity and diffusion selectivity over IRMOF-3 (with amino group) could be attributed to the improved interaction of DCM and TCM with the amino group on the MOF.

A copper-based metal–organic framework (MOF), also known as HKUST-1, was successfully synthesized, characterized, and evaluated for selective adsorption and separation of dichloromethane (DCM) and trichloromethane (TCM). The adsorption equilibria and kinetics of DCM and TCM were systematically investigated on the HKUST-1. Results showed that HKUST-1 has a high adsorption capacity for DCM (13.12 mmol g−1) and TCM (8.53 mmol g−1) at 298 K, respectively. From the kinetics results, the diffusion coefficients of DCM and TCM in HKUST-1 were estimated to be 3.73 × 10−9 cm2 s−1 and 0.44 × 10−9 cm2 s−1 at 318 K. In addition, their binary adsorption selectivity and diffusivity selectivity were predicted via the ideal adsorbed solution theory (IAST) method. The high adsorption selectivity (3.04) and diffusivity selectivity (8.93) at 318 K and 2.8 kPa indicated that HKUST-1 is a great candidate for selective adsorption and separation of DCM and TCM. Based on these results, the mechanism of adsorption and separation process has been discussed.

•Synthesis of ZIF-8/GO hybrid composites(ZG-X) in a methanol system.•ZIF-8/GO show tunable nanoscale morphology and porosity determined by GO content.•ZIF-8/GO exhibit higher gas adsorption capacity for DCM than pristine ZIF-8.•The adsorption capacity enhance with the increasing of GO content.Hybrid nanocomposites of zeolitic imidazolate framework-8 (ZIF-8) and graphene oxide (GO) were prepared in a methanol system at room temperature. The ZIF-8/GO composites exhibited tunable nanoscale morphology and porosity, both determined by the GO content. A series of characterization techniques confirmed the formation of strong interactions between ZIF-8 and GO in the synthesized composites. The as-synthesized ZIF-8/GO composites were composed of aggregated nano-sized particles, and exhibited a higher volatile organic compounds (VOCs) uptake capacity than normal ZIF-8 crystal owing to the synergistic effect between ZIF-8 and graphene oxide(GO). Also an increase in the content of GO resulted in enhancing in the VOCs adsorption capacity, and the maximum adsorption capacity for VOCs was up to 240 mg/g on ZIF-8/GO with the GO content of 15 wt%. The synergistic interactions of ZIF-8 and GO may provide a new path to fabricate novel ZIFs/GO composites for a wide range of applications such as adsorption.

•MAPbX3 perovskite single crystal with different molar ratio of organic/inorganic was prepared.•The morphology of the perovskite crystals changed with variation of the organic content.•The PL intensity of the crystal was an exponential function of molar ratio of MAX to PbX2.Most of the systematic studies on affecting photoluminescence (PL) properties in single-crystal perovskite (MAPbX3: MA = CH3NH3, X = Br, I) have focused on changing the compositions of inorganic content. Here, a serious of MAPbX3 perovskite single crystals with different molar ratio of organic to inorganic were successfully prepared by inverse temperature crystallization (ITC) method. The morphology and the PL properties of the single crystals with different ratios of organic to inorganic content were investigated. We demonstrated that the PL intensity of MAPbX3 was increased with increasing the organic content of the perovskite single crystals. It was found that morphology and lattice constants of the perovskite crystals were varied with changing of the organic content. The mechanism of the effect of organic content on optical properties of single-crystal perovskite was discussed.

The mechanical properties of a MIL-53(Al) and H2O composite (MIL-53(Al)⊃H2O) in the narrow pore (np) phase were addressed using density functional theory. The tensorial analysis of the elastic constants in the np phase provides a further support of adsorption induced stress mechanism of the breathing effect in MIL-53 and the practical mechanical properties of MIL-53(Al) in humidity condition. The adsorption of water molecules in MIL-53(Al) forms a reinforced wine-rack topological structure. The stable structure in the np phase eliminates the high anisotropy and anomalously low Young and shear moduli of the large pore phase. In addition, new soft modes which indicate the evolving path back to the large pore phase were found in the np phase.

Desorption energies of dichloromethane (CH2Cl2) and water (H2O) in a metal-organic framework, MIL-53(Al), were investigated by the combination of experimental (differential scanning calorimeter, DSC) and computational (ab-initio calculations) methods. The differences of desorption energy and natural log of the frequency factor of CH2Cl2 and H2O in MIL-53(Al) were analyzed by a thermo active process using DSC measurements. The interaction energy of guest molecules with MIL-53(Al), which correspond to the desorption in the thermal active process, was explored using ab-initio calculation. As a result of the difference in the interaction energies of H2O and CH2Cl2 in MIL-53(Al), the site near the μ2-OH groups has two potential wells. Both experimentally and computationally, MIL-53 presents the preferential adsorption of CH2Cl2 than H2O.

•Coal fly ash was used to prepare zeolite-based adsorbent for VOCs.•Single-phase zeolite NaP1 was synthesized controllably from coal fly ash.•Zeolite NaP1 showed good adsorption capacity for VOCs.Zeolites used as adsorbents for volatile organic compounds (VOCs) removal were successfully developed from coal fly ash (CFA) modified by acid solution and mixed alkali solution (NaOH and KOH). The experimental products were characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray fluorescence (XRF) and automated surface area and pore size analyzer. The results indicated that the concentration of mixed alkali solution had an important influence on the species of the zeolite phases obtained and the crystallinity of the synthetic zeolites with fixed crystallization temperature, time and ratio of Si and Al. The single phase zeolite NaP1 was obtained by controlling the synthesis process, and it showed the superiority as adsorbent for adsorption of VOCs.

Shangdong fly ash (SFA), Fangshan fly ash (FFA) and Heilongjiang fly ash (HFA) were selected as the raw materials to be used for synthesis of highly selective zeolite topology molecular sieve. Twice foaming method was studied in terms of synthetic zeolite. The experimental products were characterized by means of X-ray fluorescence (XRF), scanning electron microscope (SEM), X-ray diffraction (XRD), and automated surface area & pore size analyser. The results indicated that 10 M NaOH was chosen as modification experiment condition to process SFA. Crystallization temperature and time were 140 °C and 8 h, respectively. Zeolite topology molecular sieve was prepared with Si/Al molar ratio of 7.9, and its adsorption ratio of benzene gas was up to 66.51%.Graphical abstractHighlights► Experiments got a certain pore structure zeolite material. ► Twice foaming was achieved by changing the experiment conditions. ► Crystallization had high and low Si/Al mixture for preparing the material.

The coal fly ash (CFA) used in this study originated from a thermal power plant located in China Shandong (CS) province. During the experimental process, CS-CFA as raw materials was modified by acid solution (HCl) and alkaline solution (NaOH) with different concentration one after another for studying their effects on physical and chemical properties of coal fly ash. According to the results of characteristic analysis, CS-CFA modified by acid solution and then modified, respectively by 10 and 12 M alkaline solution were used for the preparation of X molecular sieve. X molecular sieve was prepared at different temperature and time. The effect of temperature and time on the characteristic of X molecular sieve was discussed according to the result of adsorption experiments. Moreover, by comparison with commercial activated carbon, it has been demonstrated that synthetic X molecular sieve used for industrial production is feasible.Graphical abstractHighlights► The feasibility of synthesizing adsorbents for sole VOCs with CS-CFA is verified. ► We discuss the effect of modified conditions on the characteristics of coal fly ash. ► The effect of synthesis conditions on the adsorption capacity is discussed.

A periodically poled titanium (Ti)-diffusion waveguide in near-stoichiometric MgO:LiNbO3 (SMgLN) was fabricated that exhibits a second harmonic generation (SHG) efficiency of 63%. The device shows very high resistance to photorefractive damage at room temperature. All optical wavelength conversion by difference frequency generation (DFG) has been demonstrated in a periodically poled SMgLN (PPSMgLN) with Ti-diffusion channel waveguides. The wavelength conversion efficiency was measured to be −7.3 dB with the pump power of 150 mW and the signal power of 50 mW at room temperature.