Modification and Potential Applications of Organic–Inorganic Non-Siliceous Hybrid Materials - Mesoporous Organic-Inorganic Non-Siliceous Hybrid Materials - page 80

phosphonates network from the bridging molecules and well-structured poros-
ity could increase the photoadsorption efficiency and enhance the mass trans-
fer. Correspondingly, a noticeable shift of adsorption edge to visible light region
was achieved for titanium phosphonate, in contrast to that of pure titania [ 31 ].
Interestingly, the band gap energies could be descended by lowering the pH value
of the synthesis system [ 32 ]. The shift of the absorption onset toward the lower
energy range revealed that the titanium phosphonate materials might make a better
use of solar energy. The photocatalytic activity of these materials was enhanced
because the absorption edge shifting to higher wavelengths, except for the sample
synthesized at pH = 10.5, which had a small surface area. The extension of the
adsorption to visible region of titanium-based phosphonate hybrids resulted in an
unprecedentedly impressive photoactivity under the simulated solar light illumina-
tion. When the porous structure was adjusted properly with a large surface area of
more than 1,000 m 2 g − 1 , the photocatalytic activity could be further enhanced due
to the presence of more active adsorption sites [ 17 ].
Normally, most of the wastewater produced by industrial process and house-
hold contains both organic and inorganic contaminants, such as heavy metal ions
and dyes. To cater for the need of the practical applications, a comprehensive cat-
alyst is urgently required [ 17 ]. The mixtures of Rhodamine B (RhB), Cu 2 + , and
Pb 2 + were selected as probes (Fig. 5.5 ). In the presence of ordered mesoporous
titanium phosphonate, the concentration of RhB decreased in the early 2 h and the
photodecoloraction rates decreased in the next 6 h until the dyes were completely
decomposed. A degradation efficiency of 89.2 % was achieved after 100 min of irra-
diation, which was even higher than the degree of degradation for RhB on its own
(68.4 %) after the same interval. This could be explained by a new broad absorption
Fig. 5.5 a UV-vis diffuse-reflectance spectra of PMTP-1 before and after Cu 2 + ion loading;
b one-pot heavy metal ion adsorption in the wastewater treatment as well as RhB photodegradation
using PMTP-1 under simulated solar light irradiation. Reprinted with permission from Ref. [ 17 ].
Copyright 2010, Royal Society of Chemistry