page_title: Achim Müller
section_title: Research
hierarchical_section_title: Achim Müller / Research
caption_attribution_description: English: Porous nanosized spherical polyoxomolybdate based capsule: the 20 pores with crown-ether function are filled with guanidinium cations/guests. Achim_M%C3%BCller
context_page_description: Achim Müller is a German chemist. He is Professor Emeritus at the Faculty of Chemistry, University of Bielefeld.
  His research involves mainly the chemistry of transition metals, especially with relation to nanochemistry.
  His current research relates mainly to the synthesis of spherical porous metal oxide nanocapsules Mo₁₃₂ Keplerates. Müller has also worked on simple transition metal sulphur compounds, including related hydrodesulfurization catalysis and a new type of host guest chemistry based on polyoxovanadates He has also strong interest in history and philosophy of science.
context_section_description: His current research relates mainly to bottom-up pathways towards tailor-made spherical porous metal oxide nanocapsules Mo₁₃₂ Keplerates. 
  Müller's discovery of the molecular giant spheres (Keplerates) of the type Mo₁₃₂ (diameter ca. 3 nm) and their derivatives, of the wheel shaped cluster Mo₁₅₄ (Refs. and ) and hedgehog shaped cluster Mo₃₆₈ (as large as 6 nm) has caused a paradigm shift due to the unique structural features and huge application range of these molecular nanoclusters.  
  The capsule has 20 well-defined pores with crown-ether functions which may be reversibly opened and closed. Substrates enter through these pores, and they can react to form a variety of species depending on the internal tapestry of the nanocontainer. This inorganic nanocell also allows ion transport through the cavity. Several new phenomena under confined conditions can be studied by variation of the internal ligands with hydrophilic and/or hydrophobic character, based on a variety of reactive substrates inside (for the interdisciplinary character of the whole compound class see Ref.).  These single molecules are quite large; this can be shown by taking the length of an oxygen molecule with two atoms (length 0.12 nm) as a unit, then considering Mo₃₆₈ which is 50 times larger.
  All the mentioned nanomaterials belong to a class commonly termed polyoxometalates and some special ones to the molybdenum blue family; the elucidation by Müller of the chemical nature of molybdenum blue was a real tour de force. 
  There are two older synthetic topics where Achim Müller did pioneering work. This refers to basic simple transition metal sulphur compounds, including related hydrodesulfurization catalysis and a new type of host guest chemistry based on polyoxovanadates  (for both topics see especially the three Honorary Issues under Bibliography). One paper about polyoxometalates was cited ca. 2000 times. The publications of Achim Müller were highlighted many times in the media and related magazines. Important last sentences: “Giant polyoxometalates (POMs) are of particular interest, as they are the largest inorganic molecules ever made, combined with fascinating structures and manifold applications in catalysis, medicine and material sciences. Typically, Müller‘s group has achieved great success in creating giant polyoxomolybdates (POMos) during the past two decades, establishing a series of incredibly large POMos with hundreds of Mo centers, such as {Mo₁₃₂}, {Mo₁₅₄}, {Mo₁₇₆}, {Mo₂₄₈} and {Mo₃₆₈}. Especially {Mo₃₆₈}, with more than 360 Mo atoms, still is the largest POM to date...“
caption: Porous nanosized spherical polyoxomolybdate based capsule Mo132: the 20 stepwise closable pores with crown-ether function are filled with guanidinium cation-guests (sphere surface supramolecular chemistry).
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