Organic reactions in excess water catalyzed by solid acids

A solid acid, Cs_2.5H_0.5PW₁₂O₄₀, efficiently catalyzed the reactions in which water participates such as hydrolysis of ester, hydration of alkene, and esterification, in excess water. This acidic salt was far superior in the activity to other oxide catalysts such as H-ZSM-5, Nb₂O₅, SO²⁻₄/ZrO₂, and SiO₂–Al₂O₃. When Cs_2.5H_0.5PW₁₂O₄₀ was separated from the reactant solution and reused five times for the hydrolysis of ethyl acetate repeatedly, the reaction rate was retained more than 90%. These results demonstrates that Cs_2.5H_0.5PW₁₂O₄₀ is an efficient water-tolerant solid acid.     

Liquid phase esterification of acrylic acid with 1-butanol catalyzed by solid acid catalysts

Esterification of acrylic acid with 1-butanol has been studied in a heterogeneous solid–liquid reaction system using a variety of solid acids including an acidic salt of H₃PW₁₂O₄₀, Cs_2.5H_0.5PW₁₂O₄₀. The catalytic activity (per proton) of liquid acids such as heteropolyacids, H₂SO₄, and para-toluenesulfonic acid increased as the acid strength of the solution increased, but the difference in the activity among them was not significant. In the solid–liquid reaction system, Cs_2.5H_0.5PW₁₂O₄₀ exhibited the highest catalytic activity in the unit of catalyst weight among the solid oxide catalysts, while the activity of Cs_2.5H_0.5PW₁₂O₄₀ was less than those of organic resins such as Nafion and Amberlyst 15. Contrary to the liquid acids, the specific activity values (per proton) of solid acids were significantly different. It was demonstrated that the activity of Cs_2.5H_0.5PW₁₂O₄₀ was almost retained after the addition of water, while the activities of the organic resins greatly decreased. The water-tolerant property of Cs_2.5H_0.5PW₁₂O₄₀ is presumed to be due to the hydrophobic nature of the surface.     

Selectivity and mechanism for skeletal isomerization of alkanes over typical solid acids and their Pt-promoted catalysts

Selectivities for skeletal isomerizations of n-butane and n-pentane catalyzed by typical solid acids such as Cs_2.5H_0.5PW₁₂O₄₀ (Cs2.5), SO₄²⁻/ZrO₂, WO₃/ZrO₂, and H-ZSM-5 and their Pt-promoted catalysts were compared. High selectivities for n-butane and low selectivity for n-pentane were observed over Cs2.5 and SO₄²⁻/ZrO₂, while H-ZSM-5 was much less selective, and WO₃/ZrO₂ was highly selective for both reactions. The Pt-promoted solid acids were usually selective for these reactions in the presence of H₂ except for Pt-H-ZSM-5 for n-butane isomerization. Both the acid strength and pore structure would be factors influencing the selectivity. Mechanism of skeletal isomerization of n-butane was investigated by using 1,4-¹³C₂-n-butane over Cs2.5 and Pt–Cs2.5. It was concluded that n-butane isomerization proceeded mainly via monomolecular pathway with intramolecular rearrangement on Pt–Cs2.5, while it occurred through bimolecular pathway with intermolecular rearrangement on Cs2.5. The higher selectivity on Pt–Cs2.5 would be brought about by the monomolecular mechanism. In the skeletal isomerization of cyclohexane, Pt–Cs2.5/SiO₂ was highly active and selective, while Pt–Cs2.5 was less selective. Control in the acid strength of Cs2.5 by the supporting would be responsible for the high selectivity.     

Heteropolyanions based catalysts for paraffins isomerization

n-Hexane isomerization was carried over Cs_xH_3−xPW₁₂O₄₀ catalysts promoted with Pt by mechanical mixing with a Pt on alumina catalyst. Different parameters as caesium and platinum content in the catalyst, temperature and atmosphere of heteropolyacids pre-treatment were optimized. The catalytic performances of the best catalyst were compared with those of industrial Pt promoted mordenite. 0.3 wt.% Pt-promoted Cs₂H₁PW₁₂O₄₀ pre-treated under hydrogen flow at 473 K showed the highest conversion and selectivity. Its performances are very close to those of the industrial zeolitic catalyst in the same reaction conditions. The gain in dibranched isomers selectivity is really promising for the future. With this catalyst, the reaction proceeds by a non-ideal bifunctional mechanism resulting from the superposition of a monofunctional acid and a bifunctional metal–acid mechanism.     

The hydrocracking of n-decane over bifunctional Ni-H3PW12O40/SiO2 catalysts

A series of bifunctional Ni-H₃PW₁₂O₄₀/SiO₂ catalysts for the hydrocracking of n-decane were designed and prepared. The evaluation results of the catalysts show that Ni-H₃PW₁₂O₄₀/SiO₂ catalysts possess a high activity for hydrocracking of n-decane and an excellent tolerance to the sulfur and nitrogen compounds in the feedstock. Under the reaction conditions: reaction temperature 300 °C; H₂/n-decane volume ratio of 1500; total pressure of 2 Mpa and the LHSV 2 h⁻¹, the conversion of n-decane over reduced 5%Ni-50%H₃PW₁₂O₄₀/SiO₂ catalysts is as high as 90%, the C₅⁺ selectivity equal to 70%. In order to reveal the structure and nature of the catalysts, a number of characterizations including XRD, Raman, H₂-TPD, NH₃-TPD, XPS and FT-IR of pyridine adsorption were carried out. The characteristic results show that the high activity of the catalysts and high C₅⁺ selectivity can be related to the unique structure of the H₃PW₁₂O₄₀ and its suitable acidity.     

Friedel–Crafts benzoylation of p-xylene over clay supported catalysts: novelty of cesium substituted dodecatungstophosphoric acid on K-10 clay

2,5-Dimethylbenzophenone is used extensively as a UV light stabilizer in plastics, cosmetics and films and produced by the benzoylation of p-xylene using homogeneous catalysts which pose several problems. The benzoylation of p-xylene with benzoyl chloride was carried out in a batch reactor using clay supported catalysts such as 20% (w/w) dodecatungstophosphoric (DTP) acid/K-10, 20% (w/w) Cs_2.5H_0.5PW₁₂O₄₀/K-10, 20% (w/w) ZnCl₂/K-10 and K-10 itself and sulfated zirconia. Amongst these catalysts, 20% (w/w) Cs_2.5H_0.5PW₁₂O₄₀/K-10 was found to be a better catalyst which could be reused without any further chemical treatment eliminating the effluent disposal problem. This catalyst was fully characterized. The reaction obeys the Eley–Rideal type of mechanism with a weak adsorption of the benzoylating species.     

Role of acid and redox properties on propane oxidative dehydrogenation over polyoxometallates

Cs_2.5H_1.5PV₁Mo₁₁O₄₀ heteropolyoxometallate compounds have been studied for propane oxidative dehydrogenation (ODH) in the 340–400 °C temperature range. Their redox and Brønsted acid properties have been tuned by introducing a redox metal element M such as Co^II, Fe^III, Ga^III, Ni^II, Sb^III or Zn^II in a V:M atom ratio equal to 1:1. This introduction was carried out either directly in the synthesis solution or by usual aqueous cationic exchange of protons of the solid Cs salt. TGA and FT-IR analyses allowed us to determine the extent of metal M substitution for Mo^VI in the Keggin anion and proton replacement by the M cation. It was observed that, under catalytic conditions (C₃:O₂:He=2:1:2, flow rate 15 cm³ min⁻¹, 12 h on stream), the catalysts were stable, with only a small part of the substituted elements (V and/or M) being extracted from the Keggin anion during the reaction. The presence of these metal M cations enabled us to tune the redox and acid properties of the material and to get high selectivity for propene (60–80% at 5 and 10% propane conversion) at a relatively low temperature (300–400 °C). The direct synthesis method was found more efficient than the classical cationic exchange technique for propane ODH.     

Conversion and in situ FTIR studies of direct NO decomposition over Cu-ZSM5

Copper ion-exchanged zeolites ZSM5 with SiO₂:Al₂O₃ molar ratios 33 and 53 have been subjected to activity tests for direct decomposition of NO (2000 ppm, GHSV 560–5400 h⁻¹). In situ infrared measurements were used to follow the reaction and surface and gas phase compositions. IR studies were also done in excess oxygen with rapid NO₂ formation in the gas phase.

A high level of overexchange of copper in the zeolite in combination with a low concentration of acid sites, concurrent with a high SiO₂:Al₂O₃ ratio, enhances the conversion of NO. A vibrational band at 1631 cm⁻¹ is observed below the light-off temperature and interpreted as a bridged nitrato group bound to Cu²⁺–O–Cu²⁺ dimers. This band disappears above the light-off temperature but the intensity below this temperature correlates with the catalytic activity. We interpret that these bridge bound nitrato groups act as siteblockers on the active sites for NO conversion and that a tentative reaction intermediate, N₂O₃, also binds in a bridge configuration to the same Cu²⁺–O–Cu²⁺ dimers.

A second nitrato group with unidentate coordination and vibrational bands at 1598/1575 cm⁻¹ probes isolated copper ions.

A third infrared band at 2130 cm⁻¹ confirms previous observations of -ions bound to the zeolite. We conclude that these species are coordinated to deprotonated and negatively charged sites on the zeolite and that these sites for adsorption are blocked by Cu²⁺ ion-exchange. The 2130 cm⁻¹ species appear to have no role in direct NO decomposition but the adsorption sites are crucial for the stability of the zeolite and intimately related to ion mobility in the lattice.

Prolonged immersion of the zeolite in dilute solutions of copper ions improves the catalyst performance by copper hydroxylation leading to enhanced formation of the above dimers.

A high SiO₂:Al₂O₃ ratio leads to more stable catalysts, particularly in combination with a modest overexchange of copper ions. Excessive amounts of copper escalates the deactivation of the Cu-ZSM5 catalyst through the migration and sintering of cupric oxide crystallites.     

Selective catalytic reduction of NO by C3H8 over CoOx/Al2O3: An investigation of structure–activity relationships

A series of CoO_x/Al₂O₃ catalysts was prepared, characterized, and applied for the selective catalytic reduction (SCR) of NO by C₃H₈. The results of XRD, UV–vis, IR, Far-IR and ESR characterizations of the catalysts suggest that the predominant oxidation state of cobalt species is +2 for the catalysts with low cobalt loading (≤2 mol%) and for the catalysts with 4 mol% cobalt loading prepared by sol–gel and co-precipitation. Co₃O₄ crystallites or agglomerates are the predominant species in the catalysts with high cobalt loading prepared by incipient wetness impregnation and solid dispersion. An optimized CoO_x/Al₂O₃ catalyst shows high activity in SCR of NO by C₃H₈ (100% conversion of NO at 723 K, GHSV: 10,000 h⁻¹). The activity of the selective catalytic reduction of NO by C₃H₈ increases with the increase of cobalt–alumina interactions in the catalysts. The influences of cobalt loading and catalyst preparation method on the catalytic performance suggest that tiny CoAl₂O₄ crystallites highly dispersed on alumina are responsible for the efficient catalytic reduction of NO, whereas Co₃O₄ crystallites catalyze the combustion of C₃H₈ only.     

SiO2/Nb2O5 sol–gel as a support for HRP immobilization in biosensor preparation for phenol detection

A SiO₂/Nb₂O₅ mixed oxide was prepared by a sol–gel processing method based on TEOS and NbCl₅ as precursors and HCl as catalysts. A material having a specific surface area of 703 m² g⁻¹, average pore diameter of 2.4 nm and 5 wt.% of Nb was obtained. An amperometric peroxidase-based biosensor for phenol was constructed by immobilizing the enzyme onto the SiO₂/Nb₂O₅ sol–gel matrix by adsorption and cross-linking with glutaraldehyde and mixing with graphite powder to make a modified carbon paste. The biosensor performance for phenol detection, investigated in a flow injection system, was based on mediated electron transfer of horseradish peroxidase (HRP), avoiding the direct electron transfer of HRP, which was blocked by the sol–gel matrix. With optimized conditions, a linear response range from 5 to 25 μmol dm⁻³ for phenol was obtained with a sensitivity of 3.2 nA dm³ μmol⁻¹. The detection limit of the biosensor for phenol was 0.5 μmol dm⁻³ and the analytical frequency was 27 samples h⁻¹. The biosensor response was tested for various phenol substrates and the highest response was observed for 2-amino-4-chlorophenol. During 200 determinations, the biosensor kept the same response for phenol. The modified carbon paste retained its activity during 6 months of storage under refrigeration.     

Methane combustion and CO oxidation on LaAl1−xMnxO3 perovskite-type oxide solid solutions

Structural, redox and catalytic deep oxidation properties of LaAl_1−xMn_xO₃ (x=0.0, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0) solid solutions prepared by the citrate method and calcined at 1073 K were investigated. XRD analysis showed that all the LaAl_1−xMn_xO₃ samples are single phase perovskite-type solid solutions. Particle sizes and surface areas (SA) are in the 280–1180 Å and 4–33 m² g⁻¹ ranges, respectively. Redox properties and the content of Mn⁴⁺ were derived from temperature programmed reduction (TPR) with H₂. Two reduction steps are observed by TPR for pure LaMnO₃, the first attributed to the reduction of Mn⁴⁺ to Mn³⁺ and the second due to complete reduction of Mn³⁺ to Mn²⁺. The presence of Al in the LaAl_1−xMn_xO₃ solid solutions produces a strong promoting effect on the Mn⁴⁺→Mn³⁺ reducibility and inhibits the further reduction to Mn²⁺. Both for methane combustion and CO oxidation all Mn-containing perovskites are much more active than LaAlO₃, so pointing to the essential role of the transition metal ion in developing highly active catalysts. Partial dilution with Al appears to enhance the specific activity of Mn sites for methane combustion.     

Influence of the surface area of the support on the activity of gold catalysts for CO oxidation

In the preparation of 1% Au/TiO₂ catalysts supported on either Degussa P-25 or anatase (90 m² g⁻¹) by deposition–precipitation, the gold content passes through a maximum at about the isoelectric point (pH 6), but maximum specific rates occur at pH 8–9 because the Au particle size becomes smaller as the pH is further increased. The gold uptake increases with the surface area of the support (anatase, rutile, P-25) and is complete above 200 m² g⁻¹; adsorption of the gold precursor at pH 9 is shown to be equilibrium-limited. Highest activities are found with supports of 50 m² g⁻¹. Catalysts made with high-area anatase (240 or 305 m² g⁻¹) are least active but show least deactivation.With Au/SnO₂ catalysts, gold uptake does not depend on the area of the support, and is highest at pH 7–8; very active catalysts (T₅₀ = 230–238 K) are obtained using SnO₂ of 47 m² g⁻¹. Storing a catalyst at 258 K for 1 week dramatically improves its stability. Results for Au/CeO₂ and Au/ZrO₂ catalysts confirm that moderate support areas give the most active catalysts, and suggest that surface area is often more important than chemical composition.     

Preparation of CexZr1−xO2 (x = 0.75, 0.62) solid solution and its application in Pd-only three-way catalysts

Nanoparticles of Ce_xZr_1−xO₂ (x = 0.75, 0.62) were prepared by the oxidation-coprecipitation method using H₂O₂ as an oxidant, and characterized by N₂ adsorption, XRD and H₂-TPR. Ce_xZr_1−xO₂ prepared had single fluorite cubic structure, good thermal stability and reduction property. With the increasing of Ce/Zr ratio, the surface area of Ce_xZr_1−xO₂ increased, but thermal stability of Ce_xZr_1−xO₂ decreased. The surface area of Ce_0.62Zr_0.38O₂ was 41.2 m²/g after calcination in air at 900 °C for 6 h. TPR results showed the formation of solid solution promoted the reduction of CeO₂, and the reduction properties of Ce_xZr_1−xO₂ were enhanced by the cycle of TPR-reoxidation. The Pd-only three-way catalysts (TWC) were prepared by the impregnation method, in which Ce_0.75Zr_0.25O₂ was used as the active washcoat and Pd loading was 0.7 g/L. In the test of Air/Fuel, the conversion of C₃H₈ was close to 100% and NO was completely converted at λ < 1.025. The high conversion of C₃H₈ was induced by the steam reform and dissociation adsorption reaction of C₃H₈. Pd-only catalyst using Ce_0.75Zr_0.25O₂ as active washcoat showed high light off activity, the reaction temperatures (T₅₀) of 50% conversion of CO, C₃H₈ and NO were 180, 200 and 205 °C, respectively. However, the conversions of C₃H₈ and NO showed oscillation with continuously increasing the reaction temperature. The presence of La₂O₃ in washcoat decreased the light off activity and suppressed the oscillation of C₃H₈ and NO conversion. After being aged at 900 °C for 4 h, the operation windows of catalysts shifted slightly to rich burn. The presence of La₂O₃ in active washcoat can enhance the thermal stability of catalyst significantly.     

Surfactant-mediated synthesis of metal substituted hexaaluminate from alumina sol

Manganese substituted hexaaluminate has been prepared using environmentally benign surfactants such as Triton X-100, under ambient condition with a commercial alumina sol and metal acetate precursors. The surface area of the pure alumina can be controlled to 10–70 m² g⁻¹ using cetyltrimethylammonium chloride after heating in oxygen flow at 1200°C for 6 h. The crystal structure of the obtained alumina was high purity θ-Al₂O₃. Incorporation of La and Mn leads to the formation of the high purity manganese substituted hexaaluminate with a surface area of 30–40 m² g⁻¹ which is also controllable using organic additives such as urea. The catalytic activity of the manganese substituted hexaaluminate was comparable to the sol–gel derived hexaaluminate catalyst from metal alkoxides.     

Oxidative dehydrogenation of methanol over a ruthenium-containing polyoxomolybdate supported on metal oxides chemically modified with silane coupling agent

A salt of ruthenium-containing polyoxomolybdate anion ([Ru₂Mo₁₄O₅₀]¹⁰⁻ or [Ru₂Mo₁₄O₅₂]¹⁴⁻; Ru₂Mo₁₄) was synthesized by mixing ruthenium chloride and sodium molybdate in a buffer solution (acetic acid–ammonium acetate) at pH 5. The polyanion, Ru₂Mo₁₄, was loaded on a silica carrier chemically modified with a silane coupling agent having a 1,2-diaminoethyl group (DAPS–SiO₂). X-ray diffraction, FT-IR and surface area measurements revealed that Ru₂Mo₁₄ was highly dispersed on DAPS–SiO₂ up to 20 wt.% loading. The highly dispersed Ru₂Mo₁₄ exhibited a high level of activity for oxidative dehydrogenation of methanol to formaldehyde with a high selectivity, whereas combustion of methanol occurred on the bulky salt of Ru₂Mo₁₄ and ruthenium catalyst supported on a SiO₂ carrier.     

Low-temperature H2-SCR of NO on a novel Pt/MgO-CeO2 catalyst

The selective catalytic reduction of NO by H₂ under strongly oxidizing conditions (H₂-SCR) in the low-temperature range of 100–200 °C has been studied over Pt supported on a series of metal oxides (e.g., La₂O₃, MgO, Y₂O₃, CaO, CeO₂, TiO₂, SiO₂ and MgO-CeO₂). The Pt/MgO and Pt/CeO₂ solids showed the best catalytic behavior with respect to N₂ yield and the widest temperature window of operation compared with the other single metal oxide-supported Pt solids. An optimum 50 wt% MgO-50wt% CeO₂ support composition and 0.3 wt% Pt loading (in the 0.1–2.0 wt% range) were found in terms of specific reaction rate of N₂ production (mols N₂/g_cat s). High NO conversions (70–95%) and N₂ selectivities (80–85%) were also obtained in the 100–200 °C range at a GHSV of 80,000 h⁻¹ with the lowest 0.1 wt% Pt loading and using a feed stream of 0.25 vol% NO, 1 vol% H₂, 5 vol% O₂ and He as balance gas. Addition of 5 vol% H₂O in the latter feed stream had a positive influence on the catalytic performance and practically no effect on the stability of the 0.1 wt% Pt/MgO-CeO₂ during 24 h on reaction stream. Moreover, the latter catalytic system exhibited a high stability in the presence of 25–40 ppm SO₂ in the feed stream following a given support pretreatment. N₂ selectivity values in the 80–85% range were obtained over the 0.1 wt% Pt/MgO-CeO₂ catalyst in the 100–200 °C range in the presence of water and SO₂ in the feed stream. The above-mentioned results led to the obtainment of patents for the commercial exploitation of Pt/MgO-CeO₂ catalyst towards a new NO_x control technology in the low-temperature range of 100–200 °C using H₂ as reducing agent. Temperature-programmed desorption (TPD) of NO, and transient titration of the adsorbed surface intermediate NO_x species with H₂ experiments, following reaction, have revealed important information towards the understanding of basic mechanistic issues of the present catalytic system (e.g., surface coverage, number and location of active NO_x intermediate species, NO_x spillover).     

Electrochemical properties of anatase TiO2 nanotubes as an anode material for lithium-ion batteries

Titanium oxides with a one-dimensional nanostructure are of great significance in electrochemical lithium insertion due to their high specific surface area and pore volume. In this paper, anatase TiO₂ nanotubes with diameters of about 10 nm and lengths of 200–400 nm were synthesized by a hydrothermal process. The phase structure and morphology were analyzed by X-ray diffraction, Raman scattering, and transmission electron microscopy. The electrochemical properties were investigated by constant current discharge–charge and cyclic voltammetry. There is a potential plateau at 1.73 and 1.88 V in the process of Li insertion and extraction, and the initial Li insertion/extraction capacity is 290 and 238 mAh g⁻¹ at 36 mA g⁻¹, respectively. The Li insertion capacity at the potential plateau of 1.73 V in the first cycle is about 150 mAh g⁻¹. In the 20th cycle, the reversible capacity still remains at about 200 mAh g⁻¹, and the coulombic efficiency is approximately 98%, exhibiting excellent cycling stability. The discharging capacity is about 168 mAh g⁻¹ in the 30th cycle at 210 mA g⁻¹, demonstrating a good high-rate performance. Anatase TiO₂ nanotubes might be a promising negative material for lithium-ion batteries.     

Catalytic combustion of methane over microemulsion-derived MnOx–Cs2O–Al2O3 nanocomposites

Mesostructured MnO_x–Cs₂O–Al₂O₃ nanocomposites have been synthesized by reverse microemulsion method combined with hydrothermal treatment and then applied to the catalytic combustion of methane. Compared to impregnation-derived conventional MnO_x/Cs₂O/Com-Al₂O₃ catalyst, the microemulsion-derived catalyst showed higher activity and stability for methane combustion. The T_10% of the fresh and of the 72 h aged Mn_xO–Cs₂O–Al₂O₃ were 475 and 490 °C, respectively, recommending it as a potential candidate catalyst for application in hybrid gas turbines. The homogeneous composition of the microemulsion-derived nanocomposite catalyst can hinder the loss of Cs⁺ and accelerate the formation of Cs–β-alumina phase, ensuring thus higher activity and stability for methane combustion.     

Syngas production from butane using a flame-made Rh/Ce0.5Zr0.5O2 catalyst

The capability of flame-made Rh/Ce_0.5Zr_0.5O₂ nanoparticles catalyzing the production of H₂- and CO-rich syngas from butane was investigated for different Rh loadings (0–2.0 wt% Rh) and two different ceramic fibers (Al₂O₃/SiO₂ and SiO₂) as plugging material in a packed bed reactor for a temperature range from 225 to 750 °C. The main goal of this study was the efficient processing of butane at temperatures between 500 and 600 °C for a micro-intermediate-temperature SOFC system. Our results showed that Rh/Ce_0.5Zr_0.5O₂ nanoparticles offer a very promising material for butane-to-syngas conversion with complete butane conversion and a hydrogen yield of 77% at 600 °C. The catalytic performance of packed beds strongly depended on the use of either Al₂O₃/SiO₂ or SiO₂ fiber plugs. This astonishing effect could be attributed to the interplay of homogeneous and heterogeneous chemical reactions during the high-temperatures within the reactor.     

High-quality, oriented and mesostructured organosilica monolith as a potential UV sensor

We synthesized high-quality and oriented periodic mesoporous organosilica (PMO) monoliths through a solvent evaporation process using a wide range of mole ratios of the components: 0.17–0.56 1,2-bis(triethoxysilyl)ethane (BTSE): 0.2 cetyltrimethylammonium chloride (CTACl): 0–1.8 × 10⁻³ HCl: 0–80 EtOH: 5–400 H₂O. X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images indicated that the mesoporous channels within the monolith samples were oriented parallel to the flat external surface of the PMO monolith and possessed a hexagonal symmetry lattice (p6mm). The PMO monolith synthesized from a reactant composition of 0.35 BTSE: 0.2 CTACl: 1.8 × 10⁻⁶ HCl: 10 EtOH: 10 H₂O had a pore diameter, pore volume, and surface area – obtained from an N₂ sorption isotherm – of 25.0 Å, 0.96 cm³ g⁻¹ and 1231 m² g⁻¹, respectively. After calcination at 280 °C for 2 h in N₂ flow, the PMO monolith retained monolith-shape and mesostructure. Pore diameter and surface area of the calcined PMO monolith sample were 19.8 Å, 0.53 cm³ g⁻¹ and 1368 m² g⁻¹, respectively. We performed ²⁹Si and ¹³C CP MAS NMR spectroscopy experiments to confirm the presence of Si–C bonding within the framework of the PMO monoliths. We investigated the thermal stability of the PMO monoliths through thermogravimetric analysis (TGA). In addition, rare-earth ions (Eu³⁺, Tb³⁺ and Tm³⁺) were doped into the monoliths. Optical properties of those Eu³⁺, Tb³⁺ and Tm³⁺-doped PMO monoliths were investigated by photoluminescence (PL) spectra to evaluate their potential applicability as UV sensors.