in Zeolite Y and instead is due to a barrier accessing MLCT states that are higher in
energy than the fourth MLCT state including additional singlet-in-character MLCT
states [54]. This observation further suggests that the cavity being occupied by
RuBpy in RuBpy@HKUST-1(Zn) is quite distinct from that in RuBpy@USF2
despite the similarities in MOF structure.
The fast decay associated with RuBpy@HUKUST-1(Zn) exhibits a k 0 that is
nearly an order of magnitude larger than what is observed for RuBpy in solution and
a k 1 and ΔE 1 that are similar to solution values. These observations are consistent
with RuBpy@HKUST-1(Zn) containing a population of RuBpy that is located in
regions of the framework that have larger volumes (defect regions) or at specific
surface sites. These sites allow for access to the
3 LF state as well as quenching of the
3 MLCT either from other bound RuBpy complexes (self-quenching) or possibly
other unknown exogenous quenchers.
3 RuBpy Templated MOFs
The motivation behind MOF templating arises from the desire to produce novel
topologies with unique properties, which are not accessible through direct synthetic
methods, and is a common methodology in MOF synthesis. The templating molecule has been suggested to interact with the framework precursors through weak
forces such as Van der Waals interactions, hydrogen bonding, and electrostatic
contacts [56]. In some cases, the templating molecule may remain as a guest within
the templated MOF structure. Generally, templating molecules can be divided into
seven classes including solvents, organic molecules, inorganic salts, coordination
complexes, surfactants, polymers, and gas molecules [57]. The templating effects of
solvent on MOF synthesis have been well documented. For example, Bharadwaj
et al. reported the synthesis of several different Pb(II) MOFs varying only in the
relative concentrations of water and various alcohols [58]. Zaworotko et al. reported
the synthesis of two topologies, USF3 and USF4, which differed in the presence of
benzene or chlorobenzene templating molecules, respectively [59].
Inorganic compounds may also serve as effective templating agents. One class of
transition metal complex that has demonstrated a templating ability for MOFs are the
polyoxometalates (POMs). These polyoxoanions have a wide range of applications
due to their physical and chemical properties imparted by the diversity in metal
composition. Liu and Hu have developed a synthetic method which combines
the catalytic activity of H 3 PW 12 O 40 with the high surface area and stability of
MOFs to produce cubic and octahedral crystals of the MOF NENU-3a
(Cu 12 (BTCA) 8 ÁH 3 PW 12 O 40 ) [60]. The POM interaction with the MOF precursors
is critical for the nucleation processes required to form NENU-3a. Keggin-type
POMs have also shown potential for serving as templating molecules producing
novel host-guest applications in dye adsorption and photochemistry [61].
The RuBpy and related Ru(II) polyimine complexes are emerging as an important
class of transition metal templating agents for the synthesis of photoactive MOFs for
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energy than the fourth MLCT state including additional singlet-in-character MLCT
states [54]. This observation further suggests that the cavity being occupied by
RuBpy in RuBpy@HKUST-1(Zn) is quite distinct from that in RuBpy@USF2
despite the similarities in MOF structure.
The fast decay associated with RuBpy@HUKUST-1(Zn) exhibits a k 0 that is
nearly an order of magnitude larger than what is observed for RuBpy in solution and
a k 1 and ΔE 1 that are similar to solution values. These observations are consistent
with RuBpy@HKUST-1(Zn) containing a population of RuBpy that is located in
regions of the framework that have larger volumes (defect regions) or at specific
surface sites. These sites allow for access to the
3 LF state as well as quenching of the
3 MLCT either from other bound RuBpy complexes (self-quenching) or possibly
other unknown exogenous quenchers.
3 RuBpy Templated MOFs
The motivation behind MOF templating arises from the desire to produce novel
topologies with unique properties, which are not accessible through direct synthetic
methods, and is a common methodology in MOF synthesis. The templating molecule has been suggested to interact with the framework precursors through weak
forces such as Van der Waals interactions, hydrogen bonding, and electrostatic
contacts [56]. In some cases, the templating molecule may remain as a guest within
the templated MOF structure. Generally, templating molecules can be divided into
seven classes including solvents, organic molecules, inorganic salts, coordination
complexes, surfactants, polymers, and gas molecules [57]. The templating effects of
solvent on MOF synthesis have been well documented. For example, Bharadwaj
et al. reported the synthesis of several different Pb(II) MOFs varying only in the
relative concentrations of water and various alcohols [58]. Zaworotko et al. reported
the synthesis of two topologies, USF3 and USF4, which differed in the presence of
benzene or chlorobenzene templating molecules, respectively [59].
Inorganic compounds may also serve as effective templating agents. One class of
transition metal complex that has demonstrated a templating ability for MOFs are the
polyoxometalates (POMs). These polyoxoanions have a wide range of applications
due to their physical and chemical properties imparted by the diversity in metal
composition. Liu and Hu have developed a synthetic method which combines
the catalytic activity of H 3 PW 12 O 40 with the high surface area and stability of
MOFs to produce cubic and octahedral crystals of the MOF NENU-3a
(Cu 12 (BTCA) 8 ÁH 3 PW 12 O 40 ) [60]. The POM interaction with the MOF precursors
is critical for the nucleation processes required to form NENU-3a. Keggin-type
POMs have also shown potential for serving as templating molecules producing
novel host-guest applications in dye adsorption and photochemistry [61].
The RuBpy and related Ru(II) polyimine complexes are emerging as an important
class of transition metal templating agents for the synthesis of photoactive MOFs for
166
R. W. Larsen et al.