Inorganic materials 2019
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1. Metals form solid states where the atomic orbitals overlap to form continuous bands of energy levels that allow electrons to move freely. This gives metals their conductive properties. 2. Semiconductors have a small band gap between the valence and conduction bands. Adding small amounts of impurities can increase or decrease conductivity by introducing more charge carriers. 3. Metal oxides and metal-organic frameworks use different structures and bonding to exhibit properties like magnetism, photocatalysis and gas storage that depend on their electronic band structures.
![MOF-5 (Zn4O(1,4-benzenedicarboxylate)3, 0.13-0.20 g/cm3)
consists of tetrahedral [Zn4O]6+ units that are linked together
with 1,4-benzene-dicarboxylate units. The opening in the
structure is 9.3-13.8 Å depending on the orientation of the
ring.
MOF-5 can store a significant amount of hydrogen at low
temperature (77 K: 7.1 wt % (40 bar), 10 wt % (100 bar)).
While the hydrogen storage capacity in decent at 77 K (66
g/L), its ability to store hydrogen at room temperature is
significantly lower (9.1 g/L), which limits its use as
hydrogen storage medium](https://image.slidesharecdn.com/inorganicmaterials2019-190305144504/85/Inorganic-materials-2019-66-320.jpg)
Inorganic materials 2019
- 1. Inorganic Materials UP, Dr. Chris 2019
- 2. Subjects
- 3. SOLID STATE OF METALS
- 7. Metals - Conductors Example: Combining the 2s orbitals of several Li- atoms => For each 2s AO we get one MO https://chem.libretexts.org/Textbook_Maps/General_Chemistry_Textbook_Maps/Map%3A _Chem1_(Lower)/09._Chemical_Bonding_and_Molecular_Structure/9.10%3A_Bonding_in _Metals
- 8. Finally we end up with 2 “bands” Electrons can move freely in the empty orbitals (anti-bonding MO’s)
- 9. In conductors, there is overlap between the filled and empty orbitals => Electrons from the valence band can easily move into the conduction band Conduction band Valence band
- 12. Example: Silicon as “IV semiconductor”
- 13. Example: Si crystal The closer the atoms come together, the higher the band gap will be ! LUMO HOMO https://www.youtube.com/watch?v=k_tFJin_YoQ
- 14. http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/bandper.html#c1
- 15. Group 4 elements covalent metallic
- 19. The probability to find an electron in the conductor band can be calculated as: https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Chemical_Bonding/F undamentals_of_Chemical_Bonding/Band_Structure
- 21. Fermi Level EF (metals) EF = 50% probability level to find an electron https://www.youtube.com/watch?v=zWOSAzbxTrE
- 22. For semiconductors, EF is in the middle of the band gap The higher T, the more electrons will come up to the conductive band – at 0 K, all electrons are in the valence band T up Charge carriers are electrons and holes
- 23. Example of practical applications for TiO2 (J. of CO2 utilization 1 (2013),8-17)
- 24. Photocatalysis TiO2 Light energy promotes electrons in antibonding orbitals, leaving a positive charged “hole” in the lower orbitals
- 25. Splitting of water by sunlight
- 27. https://www.azonano.com/article.aspx?ArticleID=4226 Measure the band gap energy by UV/VIS
- 29. RELATION MO DIAGRAM - BANDS
- 30. Extend MO theory Simple model: a string of 5 H-atoms 2 H-atoms can be combined to form 2 orbitals, with no node and with 1 node For 5 H atoms we get 5 combinations with 0, 1, 2, 3 and 4 nodes Nodes: 0 1 2 3 4 Draw the missing 4 MO’s for H5 And find if they are : bonding, non-bonding or anti-bonding
- 33. Vector k We can define a wavenumber for the electrons that move in a crystal: k = 2π/λ = 2πp/h k is proportional to the number of the nodes n in a molecular orbital In a linear system with N unit cells separated by distance a: (MO with n nodes) λ = 2 Na/n and k = π n / Na At the bottom of a bond with λ = infinite: k = 0 and at the top of band with the MO having N nodes: k = π/a and λ = 2a https://en.wikibooks.org/wiki/Introduction_to_Inorganic_Chemistry/Metals_and_Alloys:_ Structure,_Bonding,_Electronic_and_Magnetic_Properties
- 36. H2 in unit cell Unit cell with 2 el
- 37. • The valence band runs “uphill” • The conduction band runs “downhill” • The bands are narrower due to less overlap between the H2 molecules compared to the H atoms • The material now is not metallic anymore compared to H atom chain • The minimum energy gap between bands occurs at k = /a Valence band (full of electrons) Conduction band (empty, anti-bonding) https://cbc-wb01x.chemistry.ohio-state.edu/~woodward/ch754/bandstr.htm
- 38. DOS – Density 0f States The density of states is defined as the number of orbitals per unit of energy within a band. Because of the parabolic relation between E and k, the density of states for a 1D metallic crystal is highest near the bottom and top of the energy band where the slope of the E vs. k curve is closest to zero.
- 39. Compare Graphite - Diamond
- 40. Graphite similar to benzene
- 41. Combination of many benzene MO’s https://www.seas.upenn.edu/~chem101/sschem/conduction.html
- 42. Diamond structure only bonds https://www.seas.upenn.edu/~chem101/sschem/conduction.html
- 43. TiO2 structure Ti(4+) MOs (crystal field) Electrons in the Ti-O bonds (coming all from O2-)
- 44. Photocatalysis TiO2 Light energy promotes electrons in antibonding orbitals, leaving a positive charged “hole” in the lower orbitals
- 45. TM OXIDES
- 46. (1) Rocksalt Structure Metal monoxides MO
- 51. (2) Perovskite Structure ABO3
- 53. Preparation of metal oxides Molecular Synthesis Solid state synthesis • In a solvent • Low reaction T (-80 to 250 C) • Kinetic control eg. oxidation of alcohol: CH3CH2-OH CH3COOH (thermodynamic: oxidation leads to CO2 + H2O) • Normally solvent-free • High reaction T ( > 300 C) • Thermodynamic control Solid state reaction are slow and require high temperatures because ions have to diffuse from one crystal structure to another
- 55. Liquid to solid preparation – hydrothermal methods Similar to reaction – crystallization methods in molecular reactions: The zeolites framework is made up of SiO2 tetrahedra with the occasional substitution of Al for Si. To compensate the charge difference (Si(+4), Al(+3)) sodium cations are accommodated on the inner surface of the framework.
- 59. Zeolite-like MOFs = ZIF http://www.chemtube3d.com/solidstate/MOF-ZIF8.htm
- 60. Simplified representation The building units of Zn4O(BDC)3 (a) A central OZn4 unit filled circles are Zn) linked to six CO2 units of BDC groups (shaded circles are C). https://docs.google.com/viewer?a=v&pid=sites&srcid=ZGVmYXVsdGRvbWFpbnxwZXJp b2RpY3N0cnVjdHVyZXxneDo3YTY0YmQxYTU0ZGE4NDM4
- 61. Secondary building units of metal ions: http://cloud.crm2.univ-lorraine.fr/pdf/Manila/Okeeffe_1.pdf HKUST-1 MOF-5
- 63. Secondary building units SBU https://phys.org/news/2018-10-secondary- sbusthe-metal-organic-frameworks-mofs.html
- 64. Example MOF 5 http://science.sciencemag.org/content/309/5739/ 1350/F2
- 65. MOF-5 Science 341, (2013); Hiroyasu Furukawa et al. The Chemistry and Applications of Metal- Organic Frameworks
- 66. MOF-5 (Zn4O(1,4-benzenedicarboxylate)3, 0.13-0.20 g/cm3) consists of tetrahedral [Zn4O]6+ units that are linked together with 1,4-benzene-dicarboxylate units. The opening in the structure is 9.3-13.8 Å depending on the orientation of the ring. MOF-5 can store a significant amount of hydrogen at low temperature (77 K: 7.1 wt % (40 bar), 10 wt % (100 bar)). While the hydrogen storage capacity in decent at 77 K (66 g/L), its ability to store hydrogen at room temperature is significantly lower (9.1 g/L), which limits its use as hydrogen storage medium
- 68. Preparation
- 73. Zeolite-like MOF’s with Zn(2+) and Imidazole
- 74. Common MOF’s for gas storage
- 75. Search from Sigma Aldrich https://www.sigmaaldrich.com/materials-science/learning- center/mof-constructor.html
- 79. APPENDICES
- 80. The melting points ( ~ the strength which that atoms are held together) first raise from 1st row onwards, since more and more electrons are in valence bands. But there is a maximum in the middle of the Periodic Table: with increasing nuclear charge, the harder it is to remove electrons into the conduction band. https://chem.libretexts.org/Textbook_Maps/Ge neral_Chemistry_Textbook_Maps/Map%3A_Ch emPRIME_(Moore_et_al.)/22Metals/22.01%3A _Metallic_Bonding Melting points of metals
- 82. Acc. Chem. Res.2005,38,176-182 At level 1, a four- coordinated atom linked by ditopic linkers will almost invariantly form a structure based on diamond net. Level 2 gives examples of structures by design. Joining copper acetate paddlewheels by ditopic carboxylate linkers of the geometries shown schematically (the orange ball could stand for a phenyl group, for example) have the default structures shown (paddlewheels now shown as squares)