| Layered perovskites are not only widely studied for their interesting properties, such as superconductivity, colossal magnetoresistance, ferroelectricity, and catalytic activity, but also attract a lot of attention for their typical layered structure. In order to achieve the modify purposes in terms of the structure and properties of the parent material, selective tailored guest materials into the interlayer space of layered perovskite was possible by controlling reaction conditions. Herein, we aim to improving the synthetic techniques and approach to explore the synthesis of the novel layered perovskite material as well as to investigate of the relative structure and properties. Organic compound intercalated Ruddlesden-Popper phase layered perovskite Li2CaTaaO7 and subsequently modified by metal guests were prepared by topological chemical synthesis technology. Their structures, compositions, morphology and catalytic properties are being characterized systematically. And on this basis, bulky organic materials are introduced into the interlayer space of the layered perovskite which are delaminated into nanosheets consequently. The structure and properties of this exfoliated nanosheets are further investigated comprehensively. It will be a good contribution to the further research and practice.This work investigates four research problems around a central theme of the chemistry properties of Ruddlesden-Popper phase layered perovskite. The specific content is as follows:1. Li2CaTa2O7, the n-2 member of Ruddlesden-Popper phase, is a typical layered perovskite consisting of two-dimensional perovskite-like slabs. Its protonated derivative H2CaTa2O7 can be prepared by a complete ionic exchange. Considering the weak connection by van der Walls force between the perovskite layers, n-alkyl chains can be successfully grafted into the interlayer space of the parent material via a hydrolysis-esterification mechanism. During the chemical graft process, the c lattice parameter is magnified with preserving the layered structure of the parent material. The oxyalkyl chains were successfully introduced into the interlayer space of the perovskite by the results of the IR and solid-state 13C CP/MAS NMR spectra. Meanwhile the thermogravimetric curves illustrated the ratio for the amount of the n-alkoxyl groups grafted per perovskite unit [CaTa2O7] is approximated to 1:1. Further investigates find out a linear relationship between the c lattice parameter and the number of carbon atoms in the n-alkyl chains, which slope is calculated to be 0.478 nm per carbon atom. Thus, the n-alkyl chains can be formed on the interlayer surface of the layered perovskite with two layered arrangement, and the tilt angle between the grafted n-alkyl chains and the perovskite surface is 70°. The photocatalytic activities of the by-products are also discussed here. Among all samples tested, the 1-octadecanol derivative of H2CaTa2O7 is found to be an excellent catalyst for the catalytic reduction of organic pollutant rhodamine B and methyl orange. This work explored a new direction for application of this tailored n-propoxy derivative of H2CaTa2O7.2. On the basis of synthesis of the tailored n-propoxy derivative of H2CaTa2O7, D-Glucopyranose rings with various organic functional groups are further introduced into the interlayer space of the parent perovskite. The 1-octadecanol grafted on its perovskite derivative is replaced by the subsequently introduced D-Glucopyranose molecule. XRD results indicated that the c lattice parameter decreased from 35.026(0) A to 19.135(5) A. The IR and solid-state 13C CP/MAS NMR spectra confirmed the replacement. In order to extend the inorganic-organic hybrids, the D-Glucopyranose modified H2CaTa2O7 was further treated with [Ag(NH3)2]- solution. Silver mirror reaction can take place for the Tollens’reagent and the aldehyde groups in the D-Glucopyranose grafted. The silver nanoparticles are self-assembled on the interlayer surface of the H2CaTa2O7, and the corresponding interlayer distance is changed to be 10.816(6) A. This novel inorganic-organic hybrids exhibit excellent catalytic property. Take the reduction of the rhodamine B and 4-nitrophenol by NaBH4 as examples,3 mg as-prepared nanohybrids take only 4 minutes to completely catalytic degrade 50 mL rhodamine B at the concentration of 2.0×10-5 mol/L, and 9 minutes to degrade 50 mL 4-nitrophenol at the concentration of 1.0×10-4 mol/L. The catalytic reduction process confirmed that the inorganic-organic hybrids deposited with silver nanoparticles exhibited practical and efficient catalytic property toward the reduction of the organic pollutant. It will have a broad prospect of application in the environmental protection.3. We synthesized the Li- ions intercalated layered perovskite by treated D-glucopyranose rings modified H2CaTa2O7 with 2-butanone solution of LiClO4. Li ion deposited on the interlayer of H2CaTa2O-7 through the coordination of Li+ ions with the terminal oxygen atom on the D-glucopyranose. The noval inorganic-organic hybrid is named as Li+/glucose-H2CaTa2O7. The introduce of the Li- ions may cause the conformational changes of the D-glucopyranose in the interlayer space to some extent. Thus the c lattice parameter of the samples changed from 19.135(5) A to 19.243(1) A by the XRD analysis results. As we calculate the amount of lithium per [CaTa2O7] unit in molar ratio from the ICP result, the ratio in Li2CaTa2O7 is about 37-fold larger compared to Li/glucose-H2CaTa2O7. The AC impedance measurements on the noval hybrid exhibit improved ionic conductivity compared with Li2CaTa2O7. It is evident that the perovskite host with new morphology can significantly improve its electrochemical property when modified with additive Li-. As we can improve the catalytic properties of the perovskite host by deposited silver nanoparticle onto the interlayer surface, this two chapters suggest that through introduce different guest materials into the D-glucopyranose modified H2CaTa2O7 will help the perovskite host to obtain better performance, so as to provide an excellent host material to build novelnanohybrid. nanohybrid.4. Intercalation novel material and delamination of two-dimensional nanosheets are effective steps for exploiting the unique properties of the host material. Herein the bulky TBAOH are introduced into the interlayer space to replace the 1-octadccanol which grafted on its perovskite derivative. With the mechanical stress assistant of the ultrasounds and magnetic stirring, as the TBA- grafted on the interlayer space occurs volume expansion, the stacked perovskite layers with weak van der Walls forces began to delaminate to form a colloidal suspension of monolayer nanosheets. Microscopic observation with SEM, TEM and AFM confirmed the delamination of the parent perovskite. The thickness of the monolayer nanosheet obtained is measured to be 1.2±0.1 nm. The exfoliated nanosheets with nonporous structure own large surface area. The adsorption measurement of the as-prepared nanosheets toward Pb2- ions contained solution confirmed the exceptional uptake of 300 mg/g Pb2 ions at pH 5.0. The adsorption equilibrium was achieved in only 30 seconds. During experimental studies in simulated drinking water, the treatment capacity for Pb2- ions can achieve 1.67×105 kg water/kg adsorbent. The regeneration of the adsorbent takes 1 M HC1 to realize which greatly reducing the economy cost. Our work in the exfoliation of the perovskite develops a new direction for Ruddlesden-Popper phase layered perovskite.In the follow-up work, we can deposit metal nanoparticles onto the perovskite monolayer via self-assemble technology to further synthesize materials with novel function. |
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