On the site-specificity of polycarbonyl complexes in Cu/zeolites: combined experimental and DFT study.
The preferred Cu(+) sites and formation of mono-, di-, and tricarbonyl complexes in the Cu-FER were investigated at the periodic density functional theory level and by means of FTIR spectroscopy. The site-specificity of adsorption enthalpies of CO on Cu-FER and of vibrational frequencies of polycarbonyl complexes were investigated for various Cu(+) sites in Cu-FER. Large changes in the Cu(+) interaction with the zeolite framework were observed upon the formation of carbonyl complexes. The dicarbonyl complexes formed on Cu(+) in the main channel or on the intersection of the main and perpendicular channels are stable and both, adsorption enthalpies and CO stretching frequencies are not site-specific. The fraction of Cu(+) ions in the FER cage, that cannot form dicarbonyl can be determined from IR spectra (about 7% for the Cu-FER with Si/Al = 27.5 investigated here). The tricarbonyl complexes can be formed at the Cu(+) ions located at the 8-member ring window at the intersection of main and perpendicular channel. The stability of tricarbonyl complexes is very low (DeltaH degrees (0 K)>or=-4 kJ mol(-1)).
Bulánek
Roman
R
Department of Physical Chemistry, University of Pardubice, Nám. Cs. Legií 565, 53010 Pardubice, Czech Republic.
Drobná
Helena
H
Nachtigall
Petr
P
Rubes
Miroslav
M
Bludský
Ota
O
D002248:Carbon Monoxide / Q000737:chemistry; D003300:Copper / Q000737:chemistry*; D007473:Ion Channels; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D011076:Polycarboxylate Cement / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics; D017641:Zeolites / Q000737:chemistry*
D007473:Ion Channels; D009942:Organometallic Compounds; D011076:Polycarboxylate Cement; D017641:Zeolites; C005506:polycarbonate; D003300:Copper; D002248:Carbon Monoxide