Theore&cal Study of Adsorp&on in SIFSIX- 3- Zn Type Porous Materials

Transcription

1 Theore&cal Study of Adsorp&on in SIFSIX- 3- Zn Type Porous Materials Ahmad Ziaee* 1,2, Drahomir Chovan 1,2, Michael Zaworotko 2,3 and Syed A.M. Tofail 1,2 1 Department of Physics and Energy 2 Materials and Surface Science Ins<tute 3 Department of Chemical and Environmental Science University of Limerick, Limerick, Ireland ahmad.ziaee@ul.ie 21 st April 2015

2 Outline Introduc&on Theore&cal Approach Results and Discussion Conclusion Future Works Acknowledgement 2

3 Introduction Increasing rate of CO 2 produc&on CO 2 removal from syngas CO 2 separa&on from biogas 3 CO 2 emission rate Jos G.J. Olivier (PBL) et al, Trends in global CO 2 emissions: 2013 Report, PBL Netherlands Environmental Assessment Agency, 2013.

4 Introduction CO 2 Sorption Technologies 4

5 Introduction v Disadvantages of other sorbents: Chemical interac&on High cost of sorbent regenera&on v Advantages of MOMs: Physical interac&on Pore func&onality Tuneable structure High surface area Modular structure Basic SIFSIX- 3- Zn structure 5

6 Computa&onal Chemistry WOFOUR- 1- Ni Zaworotko and co- workers, Chem. Commun., 2013, 49, & SIFSIX- 3- Zn Molecular Interac&ons Zaworotko and co- workers, Nature, 2013, 495, In- soc- MOF Simula&ons Eddaoudi & co- workers, Angew. Chem. Int. Ed., 2007, 46,

7 Introduction Generic Force Fields Basics B C A D 7

8 Introduction Generic Force Fields Basics E I : Inversion terms (four body) For an atom like I bonded exactly to 3 other atoms J, K, L How difficult it is to put all bonds in the same plane How favourable it is to keep all bonds in the same plane E inv (ω)=1/2k inv (ω-ω o ) 2 I ω: Angle between IL bond and JIK plane ω o : Equilibrium angle which is zero for planar molecules J K L 8

9 Introduction General Calculations Monte Carlo Adsorp&on Isotherms Isosteric Heat of Adsorp&on Adsorp&on Site Loca&on Molecular Dynamics Radial Distribu&on Func&on Adsorp&on Site Loca&on Diffusion Coefficient Ab Ini&o Structure Op&miza&on Lowest Adsorp&on Energy Defini&on of New Force Field Parameters 9

10 Introduction Molecular Interaction Simulation AdsorpJon isotherms Forrest, K. et al., J. Phys. Chem. C, 2013, 117 (34), AdsorpJon sites Isosteric heat of adsorpjon(qst) Forrest, K. et al., J. Phys. Chem. C, 2013, 117 (34), Effect of pore geometry on adsorpjon

11 Introduction [Zn(pyz) 2 SiF 6 ] (SIFSIX-3-Zn) Crystal data and structure of SIFSIX- 3- Zn SIFSIX- 3- Zn unit- cell, white: H, blue: N, cyan: F, gray: C, purple: Zn, yellow: Si. Crystal System Tetragonal Space Group P4/mmm a (Ȧ) b (Ȧ) c (Ȧ) α ( o ) 90 β ( o ) 90 γ ( o ) 90 11

12 Introduction Set up Algorithm Par&al Electrosta&c Charges Yes Is the MOM structure rigid? No Define vdw interac&on parameters (Sorbate & Sorbent) Define intramolecular interac&on parameters Monte Carlo Calcula&ons Molecular Dynamics Calcula&ons 13

13 Methods Partial Charge Calculations 14 SIFSIX Fragments: white: H, blue: N, cyan: F, grey: C, purple: Zn, yellow: Si.

14 Methods Grand Canonical Monte Carlo(GCMC) 1. Par&al charges assigned to atomic centres. 2. Van der Waals poten&al parameters assigned to atomic centres. 3. Lorentz- Bertholt mixing rules used for calcula&on of different couples of atoms parameters: σ ij = σ ii + σ jj /2 ε ij = ε i ε j steps of equilibra&on and steps of produc&on 5. Canonical Monte Carlo ensemble used for Q st determina&on. 15

15 Results GCMC Calculations Q st (kjmol - 1 ) Simulated Experimental Adsorp&on (mmolg- 1) K - Simulated 298 K - Simulated 273 K - Experimental 298 K - Experimental Adsorp&on (mmolg - 1 ) Pressure (atm) Isosteric Heat of Adsorp&on(Q st ) of CO 2 in SIFSIX- 3- Zn MOM Adsorp&on Isotherms of CO 2 in SIFSIX- 3- Zn MOM 16

16 Results GCMC Calculations 150 Total Energy Average Total Energy van der Waals Energy Electrosta&c Energy Intramolecular Energy Energy (kcalmol - 1 ) SIFSIX- 3- Zn Fragments, white: H, blue: N, cyan: F, grey: C, purple: Zn, yellow: Si, red: oxygen Number of GCMC steps 17

17 Results Surface Area Analysis T. Duren et al, J. Phys. Chem. C, 2007, 111, Specific surface area based on type of sorbate CO 2 (m 2 /g) N 2 (m 2 /g) Experimental BET (m 2 /g) Accessible Specific Surface Area Connolly Specific Surface Area vdw Specific Surface Area

18 Results Molecular Dynamics Calculation g(r) Ȧ CO 2 - Si distance (Ȧ) Radial Distribu&on Func&on 19

19 Results Ab initio Calculations ΔE (KJmol- 1) Distance (Ȧ) CO 2 poten&al energy well in SIFSIX- 3- Zn cell 20

20 Results Ab initio Calculations ΔE (KJ/mol) Fluorine atom angles (degree) CO 2 SIFSIX- 3- Zn interac&on energy versus equatorial fluorine atoms angles α 21

21 ElectrostaEc PotenEal Surface QEq Method InteracEon Energy and poteneal well Ab ini&o Simula&on Bonding and Nonbonding InteracEon Generic Force Fields AdsorpEon Sites and ConformaEons Molecular Dynamics AdsorpEon Isotherms Grand Canonical Monte Carlo(GCMC) Isosteric Heat of AdsorpEon (Q st ) Canonical Monte Carlo(CMC) 22

22 Conclusion UFF force field in combina&on with Configura&onal bias Monte Carlo results adsorp&on isotherm (2.5%) and isosteric heat of adsorp&on (4.4%) which are in good agreement with experimental results. CO 2 molecules are located exactly in the centre of unit- cell between equatorial fluorine atoms. Pore geometry can be highly effec&ve in manipula&on of interac&on energy between sorbate molecule and sorbent structure. 23

23 Future Works The effect of change in metallic core on the adsorp&on proper&es. Ab ini&o based Force Field exclusively for a specific MOM. The effect of various par&al charge calcula&on methods on defining adsorp&on proper&es. The effect of pore geometry on adsorp&on proper&es of MOMs. 24

24 Acknowledgement SFI Grant No. 13/RP/B2549 Supervisors: Prof. Michael Zaworotko, Dr. Tofail Syed Dr. Drahomir Chovan (MOSAIC research Group) Dr. John Perry (Crystal Engineering Research Group) AMPS Cluster ICHEC Irish supercomputer 24 24

25 Thanks? 25 5