Hard-templated metal-organic frameworks for advanced applications

Template-directing strategies for synthesising metal-organic frameworks (MOFs) have brought about new frontiers in materials chemistry due to the possibility of applying control over crystal growth, morphology and secondarily generated pores. In particular, hard templates have resulted in performance breakthroughs in catalysis, secondary ion batteries, supercapacitance, drug delivery and molecular sieving by offering facile routes for maximising the surface areas of shape-directed MOFs. In this tutorial review, a variety of hard templates employed to direct MOFs' growth into superior nano-architectures with enhanced functionalities are discussed. Hard templates discussed here include polymers, silica nanostructures, metal oxides, layered metal hydroxides, noble metals, graphene, zeolites and MOFs themselves. These templates can be divided into three broad categories: sacrificial, semi-sacrificial and non-sacrificial templates. We elaborate on the rationale behind the choice of nanomaterials as hard templates, how hard templates direct the synthesis of MOFs, how sacrificial hard templates can be removed from the final product and what the enhanced functionalities of hard-templated MOFs are. In the case of non-sacrificial hard-templates, synergistic effects arising from the coexistence of the MOF and the hard template will also be reviewed. © 2021 The Royal Society of Chemistry

Polyhydroxyalkanoates (PHA): From production to nanoarchitecture

Among many biodegradable and biocompatible biopolymers, polyhydroxyalkanoates (PHAs), generated by microorganisms, have highly attracted attention in various fields due to their unique physicochemical properties. So far, various types of progresses have been made in environmental and engineering fields by employing PHAs. Recently, employing PHAs for nanoarchitecture has become a newly emerging trend among researchers. The intrinsic nature of PHAs has dragged them towards fabrication of nanoparticles and nanocomposites. PHAs integration with nanoparticles has been vastly noted and applied in various areas such as drug delivery, antibacterial agents and bioengineering. Here, a brief review is given to how PHAs act and are produced by microorganisms, demonstrating their properties and finally, their most recent applications are discussed in nanoarchitecture and the ways they are manipulated in the fabrication of nanomaterials. This review can shed light on the exhaustive understanding of PHA capability in nanoarchitectural basics toward the development of advanced nanomaterials in many fields such as medicine, catalysis, sensor, and adsorbents. © 2018 Elsevier B.V

Mesoporous SBA-15/PIDA as a Dendrimer Zwitterionic Amino Acid-Type Organocatalyst for Three-Component Indazolophtalazine Synthesis

A zwitterionic amino acid-like N-propyliminodiacetic acid (PIDA) organocatalyst supported to a heterogeneous surface (SBA-15/PIDA) based on iminodiacetic acid and mesoporous SBA-15, respectively was synthesized. The mesoporous hybrid catalyst was successfully characterized by SEM, TEM, TGA, FTIR, and EDS and employed in the three-component reaction of dimedone, aldehydes and phtalhydrazide for the synthesis of indazolophtalazinetrione. SBA-15/PIDA exhibited excellent catalytic activity in the reaction and showed highly recyclable and recoverable features in consecutive reaction runs. According to ab initio calculations, the recoverability of SBA-15/PIDA catalyst is attributed to the strong covalent bonding between PIDA and SBA-15. Graphical Abstract: [Figure not available: see fulltext.]. © 2019, Springer Science+Business Media, LLC, part of Springer Nature

Bispropylurea bridged polysilsesquioxane: A microporous MOF-like material for molecular recognition

Microporous organosilicas assembled from polysilsesquioxane (POSS) building blocks are promising materials that are yet to be explored in-depth. Here, we investigate the processing and molecular structure of bispropylurea bridged POSS (POSS-urea), synthesised through the acidic condensation of 1,3-bis(3-(triethoxysilyl)propyl)urea (BTPU). Experimentally, we show that POSS-urea has excellent functionality for molecular recognition toward acetonitrile with an adsorption level of 74 mmol/g, which compares favourably to MOFs and zeolites, with applications in volatile organic compounds (VOC). The acetonitrile adsorption capacity was 132-fold higher relative to adsorption capacity for toluene, which shows the pores are highly selective towards acetonitrile adsorption due to their size and arrangement. Theoretically, our tight-binding density functional and molecular dynamics calculations demonstrated that this BTPU based POSS is microporous with an irregular placement of the pores. Structural studies confirm maximal pore sizes of ∼1 nm, with POSS cages possessing an approximate edge length of ∼3.16 Å

Mechanochemically modified aluminosilicates for efficient oxidation of vanillyl alcohol

A mechanochemical protocol was applied to the synthesis of a magnetic material based on iron oxide nanoparticles and Al-SBA-15. Full characterization of the prepared Fe2O3/Al-SBA-15 evidenced the effective functionalization of the aluminosilicate surface. Particularly, TEM analysis revealed that the mechanochemical protocol did not considerable affect the hexagonal ordered structure of Al-SBA-15. DRIFT experiments of Fe2O3/Al-SBA-15 showed interesting acidic properties, which can be further associated to a good catalytic performance. The catalytic behavior of the prepared material was tested in the oxidation of vanillyl alcohol to vanillin, displaying an excellent activity and selectivity. The material resulted to be highly stable in the aforementioned reaction, without considerable decrease of conversion after 10 reuse cycles. © 2018 Elsevier B.V

Defect engineering of oxide perovskites for catalysis and energy storage: synthesis of chemistry and materials science.

Oxide perovskites have emerged as an important class of materials with important applications in many technological areas, particularly thermocatalysis, electrocatalysis, photocatalysis, and energy storage. However, their implementation faces numerous challenges that are familiar to the chemist and materials scientist. The present work surveys the state-of-the-art by integrating these two viewpoints, focusing on the critical role that defect engineering plays in the design, fabrication, modification, and application of these materials. An extensive review of experimental and simulation studies of the synthesis and performance of oxide perovskites and devices containing these materials is coupled with exposition of the fundamental and applied aspects of defect equilibria. The aim of this approach is to elucidate how these issues can be integrated in order to shed light on the interpretation of the data and what trajectories are suggested by them. This critical examination has revealed a number of areas in which the review can provide a greater understanding. These include considerations of (1) the nature and formation of solid solutions, (2) site filling and stoichiometry, (3) the rationale for the design of defective oxide perovskites, and (4) the complex mechanisms of charge compensation and charge transfer. The review concludes with some proposed strategies to address the challenges in the future development of oxide perovskites and their applications