mass filter (Fig. 3.7c). What is more, cycling tests revealed that the brown F-TiO 2Àx /
MCF sample is especially stable after five photocatalytic cycles (Fig. 3.7d). The
F-TiO 2Àx /MCF was shown to produce electrons and exhibit a much higher photocurrent response than MCF/TiO 2 under solar light irradiation. Its solar light-driven
current density is much higher than its UV and visible light-driven density as well
(Fig. 3.7e). It is worth noting that the solar light-driven current density of F-TiO 2Àx /
MCF is much higher than the sum of the current densities of the catalyst under UV
and visible light irradiation (Fig. 3.7f), which indicates that the lifetime of solar lightproduced electrons exceeds those of UV- or visible light-produced electrons. It was
concluded that the decrease of recombination sites induced by high concentration F
doping and the synergistic effect between lattice Ti
3+ -F and surface Ti
3+ -F are
responsible for the excellent absorption of solar light and photocatalytic production
of H 2 of these catalysts.
In this section, we firstly introduce the application of mesoporous TiO 2 –SiO 2
materials. It can be either applied to photodegradation of pollutants or used for
hydrogen production. Then, we have briefly listed some notable literatures and
analyzed them.
3.4 Visible Light Response Metal–Organic Frameworks
(MOFs)
In recent years, visible light responsive porous metal–organic framework
photocatalysts have been investigated deeply. Metal–organic frameworks (MOFs)
are hybrid materials composed of organic linkers and metal–oxo clusters. These
MOF materials are hot spots in research, and it can be utilized as adsorbents,
separation materials, ion-conductive materials, and catalysts. Among various highly
porous materials, metal–organic frameworks (MOFs) are unique in their degree of
tunability, structural diversity, as well as their range of chemical and physical
properties. Metal–organic frameworks (MOFs) are also known as coordination
polymers, which are crystalline materials generated by the association of metal
ions (nodes) and multitopic organic ligands (rods) [58–61]. Based on their structures,
MOFs have been considered as a promising type of materials due to its unique
attributes and open structures with periodic dual composition, which is amenable to
bottom up assembly of secondary building blocks into a desired framework
expanding or decorating a specific blueprint network topology [58, 62]. As a kind
of porous material, metal–organic frameworks (MOFs) have shown semiconductorlike characteristics in photocatalysis [63–67]. In 2009, Kataoka et al. [67] have
detected the first example of open porous metal–organic frameworks (MOFs) that
functions as an activity site for the reduction of water into hydrogen molecules in the
presence of Ru(bpy) 3
2+ ,MV
2+ , and EDTA–2Na under visible light irradiation. Also,
Zhou et al. [63] have synthesized and characterized a new metal–organic framework
(MOF-253-Pt) material through immobilizing a platinum complex in 2,203.4 Visible Light Response Metal–Organic Frameworks (MOFs)
59
MCF sample is especially stable after five photocatalytic cycles (Fig. 3.7d). The
F-TiO 2Àx /MCF was shown to produce electrons and exhibit a much higher photocurrent response than MCF/TiO 2 under solar light irradiation. Its solar light-driven
current density is much higher than its UV and visible light-driven density as well
(Fig. 3.7e). It is worth noting that the solar light-driven current density of F-TiO 2Àx /
MCF is much higher than the sum of the current densities of the catalyst under UV
and visible light irradiation (Fig. 3.7f), which indicates that the lifetime of solar lightproduced electrons exceeds those of UV- or visible light-produced electrons. It was
concluded that the decrease of recombination sites induced by high concentration F
doping and the synergistic effect between lattice Ti
3+ -F and surface Ti
3+ -F are
responsible for the excellent absorption of solar light and photocatalytic production
of H 2 of these catalysts.
In this section, we firstly introduce the application of mesoporous TiO 2 –SiO 2
materials. It can be either applied to photodegradation of pollutants or used for
hydrogen production. Then, we have briefly listed some notable literatures and
analyzed them.
3.4 Visible Light Response Metal–Organic Frameworks
(MOFs)
In recent years, visible light responsive porous metal–organic framework
photocatalysts have been investigated deeply. Metal–organic frameworks (MOFs)
are hybrid materials composed of organic linkers and metal–oxo clusters. These
MOF materials are hot spots in research, and it can be utilized as adsorbents,
separation materials, ion-conductive materials, and catalysts. Among various highly
porous materials, metal–organic frameworks (MOFs) are unique in their degree of
tunability, structural diversity, as well as their range of chemical and physical
properties. Metal–organic frameworks (MOFs) are also known as coordination
polymers, which are crystalline materials generated by the association of metal
ions (nodes) and multitopic organic ligands (rods) [58–61]. Based on their structures,
MOFs have been considered as a promising type of materials due to its unique
attributes and open structures with periodic dual composition, which is amenable to
bottom up assembly of secondary building blocks into a desired framework
expanding or decorating a specific blueprint network topology [58, 62]. As a kind
of porous material, metal–organic frameworks (MOFs) have shown semiconductorlike characteristics in photocatalysis [63–67]. In 2009, Kataoka et al. [67] have
detected the first example of open porous metal–organic frameworks (MOFs) that
functions as an activity site for the reduction of water into hydrogen molecules in the
presence of Ru(bpy) 3
2+ ,MV
2+ , and EDTA–2Na under visible light irradiation. Also,
Zhou et al. [63] have synthesized and characterized a new metal–organic framework
(MOF-253-Pt) material through immobilizing a platinum complex in 2,203.4 Visible Light Response Metal–Organic Frameworks (MOFs)
59