RhNi, and MoCo [61–69]. Lanthanide complexes have been prepared inside the
channels of ZL using the ligands reported in Table 3. The principle is to
first exchange the monovalent cations, most often K
+ , by the lanthanide ion Ln
3+
(Eu
3+ , Tb
3+ , Er
3+ , Yb
3+ , Nd
3+ ). The samples are then dried, and the ligand is added
either from the gas phase or from an inert solvent such as n-hexane. The material
must be protected from humidity if high luminescent yield is envisaged. Key for
success is that the ligands are able to diffuse deeply into the channels and, in many
cases, that they are small enough to pass each other inside. This is usually easier for
nanosized or disc-shaped ZL crystals. Different procedures have been used
depending on the envisaged properties [70–77].
3.2 Synthesis of Composites Containing Two or More
Different Guests
The properties of ZL composites containing more than one type of guests can differ
radically from those containing only one type of guests. We should distinguish
between guests that cannot pass each other inside of the tiny channels and guests
that can pass each other.
3.2.1 Guests That Cannot Pass Each Other
Many of the guests listed in Tables 1 and 2 are too bulky for gliding past each other
inside the channels as depicted in Fig. 5a. This is especially true for most molecules
the length of which surpasses the length of 1 u.c. which is 0.75 nm. Simultaneous
insertion of a mixture of two different guests is a simple possibility for, e.g., doping a
main component with some other molecules as illustrated in the “random synthesis”
scheme of Fig. 5. It was, e.g., used for studying the insertion kinetics of the two
cationic dyes Py
+ and Ox
+ by means of cation exchange [43]. The sequential
insertion of guests as illustrated in the “sequential synthesis” scheme of Fig. 5 allows
preparing many types of composites bearing a rich variety of properties. It was first
reported for cationic dyes [78] and soon extended to neutral dyes and combination of
neutral and cationic dyes leading to “sandwich”-type arrangements [16, 54]. Sequential insertion is successful for molecules which cannot glide past each other inside
the channels as explained in the scheme in Fig. 5. The first step consists of inserting a
chosen amount of a species mol1 either by ion exchange, or by gas phase adsorption,
or from a solvent, depending on its properties. This leads to a material we name
mol1-ZL. After removing species which might eventually be adsorbed at the outer
surface, the second species (mol2) is inserted. Insertion conditions have to be chosen
such that mol1 will not leave the channels or decompose during the process. Once at
least one mol2 has entered each channel on both sides, the mol1 cannot escape
Guests in Nanochannels of Zeolite L
13
channels of ZL using the ligands reported in Table 3. The principle is to
first exchange the monovalent cations, most often K
+ , by the lanthanide ion Ln
3+
(Eu
3+ , Tb
3+ , Er
3+ , Yb
3+ , Nd
3+ ). The samples are then dried, and the ligand is added
either from the gas phase or from an inert solvent such as n-hexane. The material
must be protected from humidity if high luminescent yield is envisaged. Key for
success is that the ligands are able to diffuse deeply into the channels and, in many
cases, that they are small enough to pass each other inside. This is usually easier for
nanosized or disc-shaped ZL crystals. Different procedures have been used
depending on the envisaged properties [70–77].
3.2 Synthesis of Composites Containing Two or More
Different Guests
The properties of ZL composites containing more than one type of guests can differ
radically from those containing only one type of guests. We should distinguish
between guests that cannot pass each other inside of the tiny channels and guests
that can pass each other.
3.2.1 Guests That Cannot Pass Each Other
Many of the guests listed in Tables 1 and 2 are too bulky for gliding past each other
inside the channels as depicted in Fig. 5a. This is especially true for most molecules
the length of which surpasses the length of 1 u.c. which is 0.75 nm. Simultaneous
insertion of a mixture of two different guests is a simple possibility for, e.g., doping a
main component with some other molecules as illustrated in the “random synthesis”
scheme of Fig. 5. It was, e.g., used for studying the insertion kinetics of the two
cationic dyes Py
+ and Ox
+ by means of cation exchange [43]. The sequential
insertion of guests as illustrated in the “sequential synthesis” scheme of Fig. 5 allows
preparing many types of composites bearing a rich variety of properties. It was first
reported for cationic dyes [78] and soon extended to neutral dyes and combination of
neutral and cationic dyes leading to “sandwich”-type arrangements [16, 54]. Sequential insertion is successful for molecules which cannot glide past each other inside
the channels as explained in the scheme in Fig. 5. The first step consists of inserting a
chosen amount of a species mol1 either by ion exchange, or by gas phase adsorption,
or from a solvent, depending on its properties. This leads to a material we name
mol1-ZL. After removing species which might eventually be adsorbed at the outer
surface, the second species (mol2) is inserted. Insertion conditions have to be chosen
such that mol1 will not leave the channels or decompose during the process. Once at
least one mol2 has entered each channel on both sides, the mol1 cannot escape
Guests in Nanochannels of Zeolite L
13