Abstract : The advantages of thermoelectric energy conversion technologies are briefly summarized. Recent material advances are discussed, with the focus on one-dimensional (1-D) self-assembled molecular materials as building blocks for new thermoelectric materials. The preparation, doping, and thermal characterization of phthalocyanine based materials are presented. The thermal conductivity of the doped material is orders of magnitude higher than the undoped material. This is counter intuitive against the backdrop of the Wiedemann-Franz treatment of thermal conductivity in electrical conductors from which one would expect thermal and electrical conductivity to both increase with introduction of additional charge carriers. These unusual results can be understood as a competition between the generation of an increased number of charge carriers and enhanced phonon scattering resulting from the introduction of chemical dopants.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Abstract Facile fabrication of well‐intergrown, oriented zeolite membranes with tunable chemical properties on commercially proven substrates is crucial to broadening their applications for separation and catalysis. Rationally determined electrostatic adsorption can enable the direct attachment of a b ‐oriented silicalite‐1 monolayer on a commercial porous ceramic substrate. Homoepitaxially oriented, well‐intergrown zeolite ZSM‐5 membranes with a tunable composition of Si/Al=25–∞ were obtained by secondary growth of the monolayer. Intercrystallite defects can be eliminated by using Na + as the mineralizer to promote lateral crystal growth and suppress surface nucleation in the direction of the straight channels, as evidenced by atomic force microscopy measurements. Water permeation testing shows tunable wettability from hydrophobic to highly hydrophilic, giving the potential for a wide range of applications.
Zeolite A (LTA) has many large-scale uses in separations and ion exchange applications. Because of the high aluminum content and lack of high-temperature stability, applications in catalysis, while highly desired, have been extremely limited. Herein, we report a robust method to prepare pure-silica, aluminosilicate (product Si/Al = 12–42), and titanosilicate LTA in fluoride media using a simple, imidazolium-based organic structure-directing agent. The aluminosilicate material is an active catalyst for the methanol-to-olefins reaction with higher product selectivities to butenes as well as C5 and C6 products than the commercialized silicoalumniophosphate or zeolite analogue that both have the chabazite framework (SAPO-34 and SSZ-13, respectively). The crystal structures of the as-made and calcined pure-silica materials were solved using single-crystal X-ray diffraction, providing information about the occluded organics and fluoride as well as structural information.
RTH-type zeolites are promising catalytic materials for applications that include the important methanol-to-olefins (MTO) and NOX reduction reactions. Here, RTH-type zeolites are prepared using a wide-range of imidazolium-based, cationic organic structure directing agents (OSDAs), that greatly expand the methodologies and compositions that can be used to synthesize these materials. The abilities of the OSDAs to produce RTH-type zeolites agree well with results from molecular modeling studies of predicted stabilization energies of the OSDAs in the RTH framework. The RTH-type zeolites are stable to steaming up to 900 °C and are shown to be active MTO catalysts.
