University of St Andrews

Recently, mixed anion compounds consisting of multiple anions within a single compound have gathered attention. The use of multiple anions enables unusual coordination modes and crystal structures, giving them a huge potential for new properties when compared to existing oxides or nitrides. While mixed anion compounds will occupy a central stage in materials development, the field is still quite new. In my talk, I would like to show several recent studies on mixed anion compounds with transition metals:

- Oxyhydrides: Topochemical hydride reaction allows access to titanium oxyhydrides with transition metals [1] . The labile nature of hydride anions offers unique possibilities from multistep low temperature reactions [2, 3] to catalysis. 

- Oxynitrides: Most of oxynitrides are non-magnetic, which is partly related with highly reductive synthetic condition (i.e., ammonolysis at high temperatures), but high pressure reaction enable us to obtain new magnetic oxynitrides with interesting spin structures  [4, 5].

- Phosphide-tellurides: We have recently found that layered phosphide-tellurides displays exclusive insertion of transition metals (e.g., Cd, Zn), associated with structural transition. Interestingly, the intercalation reactions proceed in solid state and at surprisingly low temperatures (e.g. 80 °C for cadmium) [6].

 

[1] Y. Kobayashi et al., Nat. Mater. 11, 507-511 (2012).

[2] T. Yajima et al., Nat. Chem. 7, 1017-1023 (2015).

[3] N. Masuda et al., J. Am. Chem. Soc. 137, 15315-15321 (2015).

[4] C. Tassel et al., Angew. Chem. Int. Ed. 54, 516-521 (2015).

[5] C. Tassel et al., Angew. Chem. Int. Ed. 55, 9667-9670 (2016).

[6] T. Yajima et al., Nat. Commun., accepted.

 

Thermodynamic laws have been key for the design of useful everyday devices from car engines and fridges to power plants and solar cells. Technology’s continuing miniaturisation to the nanoscale is expected to soon enter regimes where standard thermodynamic laws do not apply. I will give an introduction to quantum thermodynamics - the emerging research field that aims to uncover the thermodynamic laws that govern small ensembles of systems that follow non-equilibrium dynamics and can host quantum properties [1].  I will discuss a nanoscale thermodynamic experiment with heated optically trapped nanospheres in a dilute gas [2]. By developing a new theoretical model that captures the non-equilibrium situation of the particles, we were able to measure the surface temperature of the trapped spheres and observe temperature gradients on the nanoscale. In the second part of the talk I will discuss recent theoretical advances in defining thermodynamic work in the quantum regime. By introducing a process that removes quantum coherences we were able to show that work cannot only be extracted from classical non-equilibrium systems, additional work can be extracted from quantum coherences [3]. [1] Quantum thermodynamics, S. Vinjanampathy, J. Anders, Contemporary Physics 57, 545 (2016). [2] Nanoscale temperature measurements using non-equilibrium Brownian dynamics of a levitated nanosphere, J. Millen, T. Deesuwan, P. Barker, J. Anders, Nature Nanotechnology 9, 425 (2014).  [3] Coherence and measurement in quantum thermodynamics, P. Kammerlander, J. Anders, Scientific Reports 6, 22174 (2016). 

Owing to their high surface areas, tunable pore dimensions, and adjustable surface functionality, metal-organic frameworks (MOFs) can offer advantages for a variety of gas storage and gas separation applications.  In an effort to help curb greenhouse gas emissions from power plants, we are developing new MOFs for use as solid adsorbents in post- and pre-combustion CO2 capture, and for the separation of O2 from air, as required for oxy-fuel combustion.1  In particular, MOFs with open metal cation sites or diamine-functionalized surfaces are demonstrated to provide high selectivities and working capacities for the adsorption of CO2 over N2 under dry flue gas conditions.2  Multicomponent adsorption measurements further show compounds of the latter type to be effective in the presence of water,3 while calorimetry and temperature swing cycling data reveal a low regeneration energy compared to aqueous amine solutions.4  MOFs with open metal sites, such as Mg2(dobdc) (dobdc4– = 2,5-dioxido-1,4- benzenedicarboxylate), are highly effective in the removal of CO2 under conditions relevant to H2 production, including in the presence of CH4 impurities.5  Redox-active Fe2+ sites in the isostructural compound Fe2(dobdc) allow the selective adsorption of O2 over N2 via an electron transfer mechanism.6  The same material is demonstrated to be effective at 45 °C for the fractionation of mixtures of C1 and C2 hydrocarbons, and for the high-purity separation of ethylene/ethane and propylene/propane mixtures.7  Finally, it will be shown that certain structural features possible within MOFs, but not in zeolites, can enable the fractionation of hexane isomers according to the degree of branching or octane number.8

 References

1.      Sumida, K.; Rogow, D. L.; Mason, J. A.; McDonald, T. M.; Bloch, E. D.; Herm, Z. R.; Bae, T.-H.; Long, J. R. Chem. Rev. 2012, 112, 724.

2.      McDonald, T. M.; Lee, W. R.; Mason, J. A.; Wiers, B. M.; Hong, C. S.; Long, J. R. J. Am. Chem. Soc. 2012, 134, 7056.

3.      Mason, J. A.; McDonald, T. M.; Bae, T.-H.; Bachman, J. E.; Sumida, K.; Dutton, J. J.; Kaye, S. S.; Long, J. R. J. Am. Chem. Soc. 2015, 137, 4787.

4.      McDonald, T. M.; Mason, J. A.; Kong, X.; Bloch, E. D.; Gygi, D.; Dani, A.; Crocellà, V.; Giordano, F.; Odoh, S.; Drisdell, W.; Vlaisavljevich, B.; Dzubak, A. L.; Poloni, R.; Schnell, S. K.; Planas, N.; Kyuho, L.; Pascal, T.; Prendergast, D.; Neaton, J. B.; Smit, B.; Kortright, J. B.; Gagliardi, L.; Bordiga, S.; Reimer, J. A.; Long, J. R. Nature 2015, 519, 303.

5.      Herm, Z. R.; Swisher, J. A.; Smit, B.; Krishna, R.; Long, J. R. J. Am. Chem. Soc. 2011, 133, 5664.

6.      Bloch, E. D.; Murray, L. J.; Queen, W. L.; Maximoff, S. N.; Chavan, S.; Bigi, J. P.; Krishna, R.; Peterson, V. K.; Grandjean, F.; Long, G. J.; Smit, B.; Bordiga, S.; Brown, C. M.; Long, J. R. J. Am. Chem. Soc. 2011, 133, 14814.

7.      Bloch, E. D.; Queen, W. L.; Krishna, R.; Zadrozny, J. M.; Brown, C. M.; Long, J. R. Science 2012, 335, 1606.

8.      Herm, Z. R.; Wiers, B. M.; Mason, J. A.; van Baten, J. M.; Hudson, M. R.; Zajdel, P.; Brown, C. M.; Masciocchi, N.; Krishna, R.; Long, J. R. Science 2013, 340, 960.

New X-ray Free-Electron Lasers provide an opportunity to create ‘molecular movies’ of ultrafast photochemical reactions by recording series of scattering images with both spatial and temporal resolution. Our hope is that together with other ultrafast spectroscopies, this will contribute to a full understanding of photochemical reactions and the complex interplay of structure and dynamics that governs this fascinating class of chemical processes. We will discuss recent results, which include the first ever gas-phase molecular movie of the ring-opening reaction of 1,3-cyclohexadiene [1], the theoretical and conceptual framework required to interpret and analyse the experiments [2], and future directions for this new and rapidly evolving field.

[1] Minitti et al. Phys. Rev. Lett. 114 255501 (2015)

[2] Saita et al. J. Chem. Theory Comp. 12 957 (2016)