Metal-Substituted Microporous Aluminophosphates

This chapter aims to present the zeotypes aluminophosphates (AlPOs) as a complementary alternative to zeolites in the isomorphic incorporation of metal ions within all-inorganic microporous frameworks as well as to discuss didactically the catalytic consequences derived from the distinctive features of both frameworks. It does not intend to be a compilation of either all or the most significant publications involving metal-substituted microporous aluminophosphates. Families of AlPOs and zeolites, which include metal ion-substituted variants, are the dominant microporous materials. Both these systems are widely used as catalysts, in particular through aliovalent metal ions substitution. Here, some general description of the synthesis procedures and characterization techniques of the MeAPOs (metal-contained aluminophosphates) is given along with catalytic properties. Next, some illustrative examples of the catalytic possibilities of MeAPOs as catalysts in the transformation of the organic molecules are given. The oxidation of the hardly activated hydrocarbons has probably been the most successful use of AlPOs doped with the divalent transition metal ions Co2+, Mn2+, and Fe2+, whose incorporation in zeolites is disfavoured. The catalytic role of these MeAPOs is rationalized based on the knowledge acquired from a combination of the most advanced characterization techniques. Finally, the importance of the high specificity of the structure-directing agents employed in the preparation of MeAPOs is discussed taking N,N-methyldicyclohexylamine in the synthesis of AFI-structured materials as a driving force. It is shown how such a high specificity could be predicted and how it can open great possibilities in the control of parameters as critical in catalysis as crystal size, inter-and intracrystalline mesoporosity, acidity, redox properties, incorporation of a great variety of heteroatom ions or final environment of the metal site (surrounding it by either P or Al)

Growth of ZnSe and CdSe nanostructures in self-assembled block copolymer-stabilized templates

66-7

Templated synthesis of ZnSe nanostructures using lyotropic liquid crystals

2372-238

Water-based synthesis of ZnSe nanostructures using amphiphilic block copolymer stabilized lyotropic liquid crystals as templates

3121-312

Metal-organic framework hybrid adsorbents for carbon capture - A review

Metal-organic frameworks (MOFs) are three-dimensional network structures synthesized by the assembly of organic ligands with metal ions or clusters. They currently constitute one of the most promising adsorbent categories for CO2 capture given their high specific surface area and porosity, chemical versatility, and facile chemistry supporting strategic structural modifications. Indeed, many thousands of MOFs are referenced in various structural databases. Within this wide family of materials, many experience certain challenges, which often limit their use for practical applications, including their relatively poor thermal and chemical stability, cyclability, and sensitivity to trace contaminants. One promising approach to address these drawbacks lies with the hybridization of MOFs with other material counterparts to design combinatorial hybrid adsorbents exhibiting superior performance and enhanced properties, benefiting from synergetic effects from each component and interfacial properties engineering. The purpose of this work is to critically review hybridized MOF adsorbents for CO2 capture, with a prime focus on the different opportunities offered by hybridizing materials and additives to MOFs. The engineering, properties, and performance of hybridized MOFs are systematically reviewed, and opportunities and challenges are discussed. This work provides key parameters of the application of hybridized MOF adsorbents and presents recommendations for further research, thereby providing a roadmap for the synthesis and usage of these types of adsorbents for practical CO2 capture applications

Hybrid salt-enriched micro-sorbents for atmospheric water sorption

Water shortage severely impacts drought-stricken regions, with estimates indicating that almost half a billion people are affected yearly. Composites of Salt and Porous Matrix (CSPMs) are promising functional materials for water vapor sorption. Here, CSPMs were synthesized by loading SAPO-34 porous crystals with highly hygroscopic salts, namely LiCl and CaCl2, individually (mono-salt systems) or combined (binary salt systems) to enhance water sorption capacity and cyclability. The LiCl and CaCl2 content in the impregnation solution impacted the sorption behavior and equilibrium capacity of the resulting composites. Physicochemical, morphological, textural, and sorption properties were evaluated showing that the confinement of binary salts yielded the highest water uptake (0.88 gw/gads at 25 °C and 90 % RH), which was four times higher than that of the parent SAPO-34. The shape of the obtained water vapor isotherms revealed that the salts introduced into the porous structure led to significant changes in the sorption mechanism, with SAPO-34 following a Langmuir behavior (type I isotherm) and the composites a type II isotherm with associated multilayer formation due to the presence of the salts. Kinetic studies also revealed that the materials follow a PSO model dominated by water-surface interactions. Embedding different salts into the same hosting pores to support atmospheric water harvesting was therefore found to enhance capacity and cyclability compared to single inorganic porous structures toward more efficient water sorption processes