Electronic view on ethene adsorption in Cu(I) exchanged zeolites

Area of Science:

• Materials Science
• Computational Chemistry
• Catalysis

Background:

• Zeolites are crucial porous materials in catalysis.
• Copper(I) sites within zeolites are active centers for various chemical reactions.
• Understanding ethene adsorption is key to optimizing catalytic processes.

Purpose of the Study:

• To investigate ethene adsorption on isolated copper(I) sites in faujasite and MFI zeolites.
• To determine the structural, energetic, and vibrational properties of these adsorption complexes.
• To elucidate the electronic interactions governing ethene binding using advanced computational methods.

Main Methods:

• Embedded cluster method for simulating adsorption.
• Analysis of adsorption complex structures and energetic stabilities.
• Decomposition of interaction energies using natural orbitals for chemical valence.
• Calculation of C=C stretching vibrations.

Main Results:

• Ethene symmetrically binds to Cu(I) via both carbon atoms.
• Two stable adsorption configurations can exist due to Cu(I) site relaxation.
• Binding energies generally decrease with site reconstruction, but pi* back-donation can stabilize distorted structures.
• Calculated binding energy for Cu(I)-Y zeolite agrees with experimental data.
• Ethene binding in MFI zeolite is predicted to be significantly stronger than in Cu(I)-Y zeolite.

Conclusions:

• The binding of ethene to Cu(I) sites in zeolites is well-described by computational methods.
• The type of copper coordination to framework oxygen nodes dictates the vibrational frequencies.
• Observed IR spectral features in Cu(I)-faujasite are explained by the coexistence of different adsorption complexes.