A new concept of luminescent host-guest materials was developed by introduction of Eu3+ into COK-16, a HKUST-1 type hybrid metal-organic framework (MOF) with cation exchange properties. In Eu@COK-16, the luminescent ion resides in the pore system of the MOF. The luminescent properties of Eu@COK-16 have been studied based on excitation and emission, allowing analysis of intramolecular energy-transfer processes from the COK-16 host to the exchanged Eu3+ ions. Both, the framework trimesate (BTC) and encapsulated [PW12O40] 3- ions contribute to energy transfer. Since the antenna molecules (BTC) are part of the framework structure and [PW12O40]3- ions only partly occupy one of the three types of cavities in the structure, a large fraction of the pore volume in this host sensitized luminescent MOF remains available for catalysis applications or adsorption of additional sensitizing molecules. The
material structure was determined from a combination of elemental analysis, XAS, XRD, electron and luminescence spectroscopy.