Electron spin resonance studies of copper complexes incorporated in zeolites and mesoporous molecular sieves

Different zeolites like ZSM-5, NaY, and mesoporous MCM-41 materials have be en synthesised. Two strategies were used to incorporate two different organ ic copper complexes (pyridine, ethylenediamine) into the porous materials: ii) incorporation of the cupric ion by ion-exchange and the subsequent co-o rdination of the organic ligand molecules by diffusion; and (ii) incorporat ion of the complex itself into the molecular sieves. To characterise the in teractions between the host-guest system and to study the symmetry of the c omplexes the electron spin resonance (ESR) and the electron spin echo envel ope modulation spectroscopy (2D ESEEM) were applied. The results show that it is possible to incorporate copper complexes by both ion exchange and inc orporation procedures in all studied zeolite/molecular sieves. Within the M CM-41 molecular sieve it could show that the copper pyridine complexes are not attached to the inner surface of the mesopores in samples where solvent molecules are still present. On the other side, the copper complexes can b e immobilised by washing and drying the zeolite/molecular sieve material at ambient temperatures. Some of the complexes form agglomerates that might s uggest the existence of diffusion barriers such as stacking faults in the M CM-41 structure. (C) 1999 Elsevier Science B.V. All rights reserved.