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
Outline Introduc&on Theore&cal Approach Results and Discussion Conclusion Future Works Acknowledgement 2
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.
Introduction CO 2 Sorption Technologies 4
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
Computa&onal Chemistry WOFOUR- 1- Ni Zaworotko and co- workers, Chem. Commun., 2013, 49, 9809-9811. & SIFSIX- 3- Zn Molecular Interac&ons Zaworotko and co- workers, Nature, 2013, 495, 80-84. In- soc- MOF Simula&ons Eddaoudi & co- workers, Angew. Chem. Int. Ed., 2007, 46, 3278-3283. 6
Introduction Generic Force Fields Basics B C A D http://cmm.info.nih.gov/modeling/guide_documents/molecular_mechanics_document.html 7
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
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
Introduction Molecular Interaction Simulation AdsorpJon isotherms Forrest, K. et al., J. Phys. Chem. C, 2013, 117 (34), 17687-17698. 10 AdsorpJon sites Isosteric heat of adsorpjon(qst) Forrest, K. et al., J. Phys. Chem. C, 2013, 117 (34), 17687-17698. Effect of pore geometry on adsorpjon
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) 7.1151 b (Ȧ) 7.1151 c (Ȧ) 7.5747 α ( o ) 90 β ( o ) 90 γ ( o ) 90 11
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
Methods Partial Charge Calculations 14 SIFSIX Fragments: white: H, blue: N, cyan: F, grey: C, purple: Zn, yellow: Si.
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 4. 1.0 10 6 steps of equilibra&on and 3.0 10 6 steps of produc&on 5. Canonical Monte Carlo ensemble used for Q st determina&on. 15
Results GCMC Calculations 50 3 45 40 2.5 Q st (kjmol - 1 ) 35 30 25 20 15 10 5 Simulated Experimental Adsorp&on (mmolg- 1) 2 1.5 1 0.5 273 K - Simulated 298 K - Simulated 273 K - Experimental 298 K - Experimental 0 0 0.5 1 1.5 2 2.5 3 Adsorp&on (mmolg - 1 ) 0 0 0.2 0.4 0.6 0.8 1 1.2 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
Results GCMC Calculations 150 Total Energy Average Total Energy van der Waals Energy Electrosta&c Energy Intramolecular Energy 100 50 Energy (kcalmol - 1 ) 0-50 - 100 0 500000 1000000 1500000 2000000 2500000 3000000-150 - 200 SIFSIX- 3- Zn Fragments, white: H, blue: N, cyan: F, grey: C, purple: Zn, yellow: Si, red: oxygen. - 250 Number of GCMC steps 17
Results Surface Area Analysis T. Duren et al, J. Phys. Chem. C, 2007, 111, 15350-15356 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 325.19 145.67 250 Connolly Specific Surface Area 1739.54 1697.64 - vdw Specific Surface Area 3332.40 3332.40-18
Results Molecular Dynamics Calculation 30 25 g(r) 20 15 5.29 Ȧ 10 5 0 3 4 5 6 7 CO 2 - Si distance (Ȧ) Radial Distribu&on Func&on 19
Results Ab initio Calculations 0-10 0 1 2 3 4 5-20 ΔE (KJmol- 1) - 30-40 - 50-60 - 70 Distance (Ȧ) CO 2 poten&al energy well in SIFSIX- 3- Zn cell 20
Results Ab initio Calculations ΔE (KJ/mol) - 50-52 - 54-56 - 58-60 - 62-64 - 66 0 5 10 15 20 25 30 35 40 45 50 Fluorine atom angles (degree) CO 2 SIFSIX- 3- Zn interac&on energy versus equatorial fluorine atoms angles α 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
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
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
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
Thanks? 25 5