isotope labeling experiments. They found that the dehydrocyclization reaction of
hexane over Pt-ZL composites is controlled by hexane entry into the wider lobes of
the ZL channels where the Pt clusters reside. In contrast to non-microporoussupported Pt catalysts, the tiny windows of the ZL channels allow hexane to pass
through one by one to the larger lobes containing the Pt clusters. This controlled
diffusion of hexane is the reason for the high stability and selectivity of the catalyst,
most likely because it inhibits the bimolecular reactions that lead to coke formation
and catalyst deactivation [199]. Roduner et al. studied the structure, size, hydrogen
uptake, and magnetic properties of Pt cluster in ZL [66, 67]. The activity of discshaped and of nanosized ZL supports for bimetallic RhNi clusters was compared in a
study regarding metal-ZL-catalyzed hydrogen production in biogas reforming processes [39]. Restructuring of the metal cluster, at least in the initial phase of activity,
is expected to occur. This has been very nicely demonstrated in an experiment where
atomic layer deposition was used to synthesize PtCo clusters of 0.6–0.8 nm diameter
inside of the ZL channels. Restructuring during the aromatization process of
n-heptane leads to improved and impressing performance during the initial 5 h
reaction time [69]. ZL with its one-dimensional channels shows excellent catalytic
performances in the selective hydrogenation and aromatization. The small pore size,
however, strongly hinders the diffusion of bulky molecules in bimetallic ZL
supported clusters used for hydrodesulphurization (HDS) of FCC gasoline. This
leads to the idea to combine the properties of the nanoporous ZL with those of
mesoporous MCM-41 and to decorate this with bimetallic MoCo clusters. The
so-obtained composites showed very interesting multifunctional performances in
the HDS reaction of full-range FCC gasoline [200, 201].
9 Artificial Photonic Antenna Systems for Light
Harvesting, Transport, and Trapping
An artificial photonic antenna is an organized multi-component arrangement in
which several chromophores absorb the incident light and channel the electronic
excitation energy to a common acceptor component [202]. We observed that ZL can
be used as a host for organizing different chromophores into well-defined patterns
[78, 203]. The question aroused if this could be used for preparing materials
consisting of appropriately chosen chromophores organized by ZL as a host to
mimic important properties of the natural antenna system of green plants which
consists of several hundred chlorophyll molecules closely packed in a hydrophobic
environment. The results of our calculations, which were based on a homogeneous
Markoffian random walk of FRET (Förster Resonance Energy Transfer) [204, 205]
processes, in which each energy transfer step is incoherent and occurs from a
thermalized initial state, were so encouraging that we decided to study its implication
in a systematic way and to design and realize artificial antenna systems based on ZL
as an organizing and stabilizing host [151]. The orientation inside the channels of the
Guests in Nanochannels of Zeolite L
49
hexane over Pt-ZL composites is controlled by hexane entry into the wider lobes of
the ZL channels where the Pt clusters reside. In contrast to non-microporoussupported Pt catalysts, the tiny windows of the ZL channels allow hexane to pass
through one by one to the larger lobes containing the Pt clusters. This controlled
diffusion of hexane is the reason for the high stability and selectivity of the catalyst,
most likely because it inhibits the bimolecular reactions that lead to coke formation
and catalyst deactivation [199]. Roduner et al. studied the structure, size, hydrogen
uptake, and magnetic properties of Pt cluster in ZL [66, 67]. The activity of discshaped and of nanosized ZL supports for bimetallic RhNi clusters was compared in a
study regarding metal-ZL-catalyzed hydrogen production in biogas reforming processes [39]. Restructuring of the metal cluster, at least in the initial phase of activity,
is expected to occur. This has been very nicely demonstrated in an experiment where
atomic layer deposition was used to synthesize PtCo clusters of 0.6–0.8 nm diameter
inside of the ZL channels. Restructuring during the aromatization process of
n-heptane leads to improved and impressing performance during the initial 5 h
reaction time [69]. ZL with its one-dimensional channels shows excellent catalytic
performances in the selective hydrogenation and aromatization. The small pore size,
however, strongly hinders the diffusion of bulky molecules in bimetallic ZL
supported clusters used for hydrodesulphurization (HDS) of FCC gasoline. This
leads to the idea to combine the properties of the nanoporous ZL with those of
mesoporous MCM-41 and to decorate this with bimetallic MoCo clusters. The
so-obtained composites showed very interesting multifunctional performances in
the HDS reaction of full-range FCC gasoline [200, 201].
9 Artificial Photonic Antenna Systems for Light
Harvesting, Transport, and Trapping
An artificial photonic antenna is an organized multi-component arrangement in
which several chromophores absorb the incident light and channel the electronic
excitation energy to a common acceptor component [202]. We observed that ZL can
be used as a host for organizing different chromophores into well-defined patterns
[78, 203]. The question aroused if this could be used for preparing materials
consisting of appropriately chosen chromophores organized by ZL as a host to
mimic important properties of the natural antenna system of green plants which
consists of several hundred chlorophyll molecules closely packed in a hydrophobic
environment. The results of our calculations, which were based on a homogeneous
Markoffian random walk of FRET (Förster Resonance Energy Transfer) [204, 205]
processes, in which each energy transfer step is incoherent and occurs from a
thermalized initial state, were so encouraging that we decided to study its implication
in a systematic way and to design and realize artificial antenna systems based on ZL
as an organizing and stabilizing host [151]. The orientation inside the channels of the
Guests in Nanochannels of Zeolite L
49