H3PW12O40/mpg‐C3N4 as an efficient and reusable catalyst in the alkylation of o‐xylene and styrene

A heterogeneous catalyst (HPW/mpg‐C₃N₄) for the alkylation of o‐xylene and styrene reaction was acquired by the immobilization of phosphotungstic acid (HPW) on mesoporous graphitic carbon nitride (mpg‐C₃N₄) through electrostatic interaction. The results of Fourier transform infrared spectroscopy (FT‐IR), X‐ray powder diffraction (XRD), X‐ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) proved that HPW was successfully immobilized on the protonated mpg‐C₃N₄ by electrostatic interaction. The textural properties and morphology of HPW/mpg‐C₃N₄ were characterized by N₂ adsorption–desorption, scanning electron microscopy (SEM). Among them, 40% HPW/mpg‐C₃N₄ displays the best catalytic performance in the alkylation reaction with 91.8% yield and 96.5% selectivity to 1, 2‐diphenylethylane. Moreover, protonated mpg‐C₃N₄ not only displays as a support to facilitate great dispersion of HPW but also promotes the alkylation product diffusion effectively. Besides, the HPW/mpg‐C₃N₄ catalyst could be recycled easily without significant loss of catalytic activity, which is demonstrate by the recyclability of HPW/mpg‐C₃N₄ catalyst test.     

Preparation,characterization and heterogeneous catalytic applications of GO/Fe3O4/HPW nanocomposite in chemoselective and green oxidation of alcohols with aqueous H2O2

Graphene oxide ‐ Fe₃O₄ ‐ NH₃⁺H₂PW₁₂O₄₀ ^‐ magnetic nanocomposite (GO/Fe₃O₄/HPW) was prepared by linking amino ‐ functionalized Fe₃O₄ nanoparticles (Fe₃O₄ ‐ NH₂) on the graphene oxide (GO), and then grafting 12 ‐ tungstophosphoric acid (H₃PW₁₂O₄₀) on the graphene oxide ‐ magnetite hybrid (GO ‐ Fe₃O₄ ‐ NH₂). The obtained GO/Fe₃O₄/HPW nanocomposite was well characterized with different techniques such as FT ‐ IR, TEM, SEM, XRD, EDX, TGA ‐ DTA, AGFM, ICP and BET measurements. The used techniques showed that the graphene oxide layers were well prepared and the various stages of preparation of the GO/Fe₃O₄/HPW nanocomposites successfully completed. This new nanocomposite displayed excellent performance as a heterogeneous catalyst in the oxidation of alcohols with H₂O₂. The as ‐ prepared GO/Fe₃O₄/HPW catalyst was more stable and recyclable at least five times without significantly reducing its catalytic activity.     

HPW/PDMAEMA‐b‐PMAA/ZIF‐8 Ternary Lamellar Composite and the Photocatalytic Degradation of Methylene Blue

PDMAEMA‐b‐PMAA block copolymers were prepared by the sequential RAFT polymerization of DMAEMA and tBMA, followed by hydrolysis. Phosphotungstic acid (HPW) was anchored to the PDMAEMA blocks through electrostatic interactions and the as‐obtained HPW/PDMAEMA‐b‐PMAA was added to the synthesis of ZIF‐8. During the formation of ZIF‐8, the PMAA blocks coordinated to the Zn²⁺ ions through their carboxy groups, along with the HPW groups that were anchored to the PDMAEMA blocks. In this way, the block copolymer could consolidate the interactions between HPW and ZIF‐8 and prevent the leakage of HPW. Finally, the HPW/PDMAEMA‐b‐PMAA/ZIF‐8 ternary lamellar composite was obtained and the structure of the HPW/PDMAEMA‐b‐PMAA/ZIF‐8 hybrid material was characterized by using powder X‐ray diffraction (PXRD), X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). As a photocatalyst, the HPW/PDMAEMA‐b‐PMAA/ZIF‐8 ternary lamellar composite showed excellent photoactivity for the degradation of methylene blue (MB). The rate of degradation of MB was 0.0240 min^?1, which was 7.5‐times higher than that of commercially available P25 (0.0032 min^?1). In the presence of H₂O₂, the kinetic degradation parameters of the composite reached 0.0634 min^?1, which was about 19.8‐times higher than that of P25.     

Electrochromatographic performance of graphene and graphene oxide modified silica particles packed capillary columns

Graphene oxide functionalized silica microspheres (GO@SiO₂) were synthesized based on condensation reaction between amino from aminosilica particles and carboxyl groups from GO. Reduction of GO@SiO₂ with hydrazinium hydroxide generated graphene modified silica particles (G@SiO₂). GO@SiO₂ and G@SiO₂ packed capillary columns for capillary electrochromatography were thereafter fabricated by pressure slurry packing with single‐particle frits. GO of 0.3 mg/mL in dispersion solution for GO@SiO₂ synthesis was considered as a compromise between retaining and column efficiency whereas GO@SiO₂ of 20 mg/mL in slurries for column packing was chosen for a homogenous and tight bed. Optimum mobile phases were acquired considering both electroosmotic flow and resolution at an applied voltage of −6 kV as the following: acetonitrile/phosphate buffer (10 mM, pH 7.0), 75:25 (v/v) for polycyclic aromatic hydrocarbons and 50:50 (v/v) for aromatic compounds. A comparison was made between electrochromatographic performances for three PAHs (naphthalene, fluorene and phenanthrene) and three aromatic compounds of various polarities (toluene, aniline and phenol) on bare aminosilica, GO@SiO₂ and G@SiO₂ packed columns, which proved the contribution of alone or combinational actions of solvophobic effect and π‐π electron stacking as well as hydrogen bonds to retaining behaviors by GO@SiO₂ and G@SiO₂. Well over‐run, over‐day and over‐column precisions (retention time: 0.3–1.4, 1.1–3.8 and 2.8–5.2%, respectively; peak area: 2.6–6.5, 4.8–8.3 and 6.5–12.6%, respectively) of GO@SiO₂ packed columns were a powerful proof for good reproducibility. Analytical characteristics of GO@SiO₂ packed capillary columns in CEC analysis of fresh water were evaluated with respect to linearity (R² = 0.9961–0.9989) over the range 0.1 to 100 mg/L and detection limits of 9.5 for naphthalene, 12.6 for fluorene and 16.2 μg/L for phenanthrene. Further application to fresh water increased the visibility of the proposed material, where good spike recoveries in the range 89–96% were offered.     

Photocatalytic Degradation of Imidacloprid by Phosphotungstic Acid Supported on a Mesoporous Sieve MCM‐41

Solid catalysts consisting of polyoxometalates (POM) namely phosphotungstic acid H₃PW₁₂O₄₀ (HPW) supported on a mesoporous sieve MCM‐41 have been prepared and characterized by FT‐IR, X‐ray diffraction, nitrogen adsorption and high resolution transmission electron microscope (HRTEM). The HPW/MCM‐41 with different HPW loadings from 10 to 60 wt% possess large specific surface area and rather uniform mesopores. Keggin structure of HPW retains on the prepared composite catalysts. The photocatalytic performance of HPW/MCM‐41 was examined by degradation of a durable pesticide imidacloprid. It is found that the prepared photocatalysts exhibit high activity under irradiation of 365 nm monochromatic light. For 50 mL of imidacloprid (10 mg/L), conversion of imidacloprid using 20 mg of HPW/MCM‐41 with 50 wt% loading level and calcined at 300°C reaches 58.0% after 5 h irradiation.     

Promotion of oxidative desulfurization performance of model fuel by 3DOM Ce-doped HPW/TiO2 material

Phosphotungstic acid (HPW) supported on Ce-doped three-dimensional ordered macroporous (3DOM) TiO₂ catalysts are studied in catalytic oxidation desulfurization (ODS) of model oil. The structural and textural of as-synthesized catalysts are characterized by N₂ adsorption, XRD, Raman spectroscopy, SEM-EDS, TEM, FT-IR, XPS, UV–Vis and ICP. These results upheld the existence of periodically arranged macroporous structure of catalyst, with Keggin-type of HPW dispersed homogeneously on TiO₂ matrix. Among these 3DOM Ce-doped HPW/TiO₂ materials, catalyst with 15 wt.% cerium dosage exhibits best ODS performance, which oxidized 99.8% of dibenzothiophene (DBT) into corresponding sulfone within 40 min. The excellent ODS performance of 3DOM Ce-doped HPW/TiO₂ catalyst is related to the common influence of more oxygen vacancies produced by electron transformation between Ce³⁺ and Ce⁴⁺. The chemisorbed oxygen on the surface catalyst will facilitate the selective oxidation of sulfides to sulfones. Moreover, the 3DOM structure of catalyst will further promote the mass transfer of reactants and products on the pore channel. The as-prepared catalyst shows excellent reusability in the ODS system, no obviously decrease in catalytic activity even after 6 runs.     

Synergistic effect of Zr-incorporated framework and subsequent deposition of PEHA towards efficient and reusable HPW/PEHA/ZrSBA-15 composites

Heteropolyacid-based catalysts with molecular level distributions of surface functionalities were synthesized by anchoring phosphotungstic acid (HPW) onto the pentaethylenehexamine (PEHA) layers stabilized by platelet ZrSBA-15 with short mesochannels. Namely, the presence of zirconium species in pore walls could significantly improve the surface acidity to attract and stabilize PEHA species, leading to a stronger interaction between them and a superiority to make HPW species highly stable. Standard characterizations of XRD, SEM, TEM, FT-IR, TG, N₂ adsorption–desorption and N elemental analyses were preserved to demonstrate the synergistic effect. The resulting composite were investigated for the oxidation of benzaldehyde to benzoic acid in the H₂O₂-mediated environment, the catalyst 25 % HPW/PEHA/ZrSBA-15 screened high yield for benzoic acid (~99.7 %). Besides, various reaction parameters such as reaction temperature, reaction time, the amount of hydrogen peroxide and catalyst reusability were also investigated for the oxidation of benzaldehyde to benzoic acid with a target to confirm the validity of the catalyst.     

银含量对二氧化硅固载磷钨酸银催化四氢呋喃聚合反应性能的影响

通过共浸渍法合成了一系列担载型杂多酸银盐催化剂Ag_xH_3-xPW/SiO₂ (x=0.5, 1.0, 1.5, 2.0, 2.5, 3.0),由于催化剂在极性溶剂中的不溶性, 在合成聚四氢呋喃的反应中显示了高反应活性和稳定性能. Ag离子取代含量和银盐的担载量对催化剂活性会产生显著影响. Ag 离子含量的不同会导致磷钨酸银盐的晶相结构和催化剂的酸性质发生变化. x=2.0 时, 催化剂Ag₂HPW/SiO₂达到最大酸强度和最高催化聚合反应活性. 当银盐Ag₂HPW的担载量为30% (质量分数)时, 催化剂能达到高分散度和高的四氢呋喃聚合反应活性. 与普通二氧化硅担载的磷钨酸催化剂HPW/SiO₂对比, 担载型磷钨酸银盐30%Ag₂HPW/SiO₂拥有优异的重复使用性能, 循环4 次后催化活性只有轻微下降. 通过引入Ag离子合成的新型担载磷钨酸银盐30%Ag₂HPW/SiO₂, 反应稳定性能明显改进, 得到拥有稳定平均分子量的产物聚四氢呋喃.     

Mesoporous zirconium–silica nanocomposite modified with heteropoly tungstophosphoric acid catalyst for ultra-deep oxidative desulfurization

An adsorbent catalyst was proposed to reduce the leaching of active species of the catalyst and enhance the kinetics of the oxidative desulfurization (ODS) reaction of dibenzothiophene (DBT) from model diesel fuel. By loading phosphotungstic acid (HPW) species onto a zirconium-modified hexagonal mesoporous silica (Zr-HMS), a novel catalyst was synthesized and utilized for the ODS process. An ultrafast ODS kinetics was specifically identified using 20%HPW/Zr-HMS as catalyst. Within 30 min, more than 95% of the 350 ppm DBT content of the model fuel was oxidized by H₂O₂. The synthesized catalyst retained its sulfur removal ability even after five subsequent ODS reactions and the leaching of HPW species was found to be suppressed successfully. Overall, this new reusable catalyst provided an alternative for highly efficient ultra-deep desulfurization process.     

Oxidative Desulfurization of Diesel Oil Using Mesoporous Phosphotungstic Acid/SiO2 as Catalyst

Ordered mesoporous phosphotungstic acid/SiO₂ (HPW/SiO₂) with Keggin‐type heteropolyacids (HPAs) encapsulated into a SiO₂ framework has been synthesized and used as the catalyst for oxidative desulfurization of diesel fuel. The sulfur compounds in diesel were oxidized and removed at a temperature range of 50–80 °C with H₂O₂ as the oxidant and acetonitrile as the extraction agent. The sulfur content in diesel was reduced to as low as 48–86 μg/g from the initial level of 438 μg/g. The loss in catalytic activity was negligible even after five cycles of use, and the reduction of the sulfur content was enhanced with increasing the immobilized phosphotungstic acid (HPW) concentration. Oxidation of model compounds showed that in the heterogeneous system both the electron density and the steric hindrance affected the reactivity of these sulfur compounds. The reactivities of these sulfur compounds studied in this work followed the order of dibenzothiophene > 4,6‐dimethydibenzothiophene > benzothiophene.     

New Insights into Keggin‐Type 12‐Tungstophosphoric Acid from 31P MAS NMR Analysis of Absorbed Trimethylphosphine Oxide and DFT Calculations

The acid and transport properties of the anhydrous Keggin‐type 12‐tungstophosphoric acid (H₃PW₁₂O₄₀; HPW) have been studied by solid‐state ³¹P magic‐angle spinning NMR of absorbed trimethylphosphine oxide (TMPO) in conjunction with DFT calculations. Accordingly, ³¹P NMR resonances arising from various protonated complexes, such as TMPOH⁺ and (TMPO)₂H⁺ adducts, could be unambiguously identified. It was found that thermal pretreatment of the sample at elevated temperatures (≥423 K) is a prerequisite for ensuring complete penetration of the TMPO guest probe molecule into HPW particles. Transport of the TMPO absorbate into the matrix of the HPW adsorbent was found to invoke a desorption/absorption process associated with the (TMPO)₂H⁺ adducts. Consequently, three types of protonic acid sites with distinct superacid strengths, which correspond to ³¹P chemical shifts of 92.1, 89.4, and 87.7 ppm, were observed for HPW samples loaded with less than three molecules of TMPO per Keggin unit. Together with detailed DFT calculations, these results support the scenario that the TMPOH⁺ complexes are associated with protons located at three different terminal oxygen (O_d) sites of the PW₁₂O₄₀³⁻ polyanions. Upon increasing the TMPO loading to >3.0 molecules per Keggin unit, abrupt decreases in acid strength and the corresponding structural variations were attributed to the change in secondary structure of the pseudoliquid phase of HPW in the presence of excessive guest absorbate.     

烷基膦酸促进负载磷钨酸催化异丁烷/丁烯烷基化反应

异丁烷/丁烯烷基化是生产高辛烷值汽油的重要反应,目前主要采用液体强酸为催化剂,而固体催化剂用于该反应的性能均不理想。我们设计合成出十六烷基膦酸(HDPA)修饰的氧化硅负载型磷钨酸纳米多级结构催化剂(HDPA-HPW/SiO2),其结构与悬铃木果实相似。通过X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、透射电子显微镜镜(TEM)、氮气吸附-脱附、异丁烷吸附-脱附等对该催化剂进行了表征,并使用固定床微型反应器评价了其对异丁烷/丁烯烷基化反应的催化性能。结果表明,HDPA的外围修饰增强了催化剂对烃类反应物的吸附,减少了烯烃聚合副反应和催化剂表面积碳的产生,提高了高辛烷值产物的选择性,延长了催化剂的寿命。     

Selective hydrolysis of cellulose for the preparation of microcrystalline cellulose by phosphotungstic acid

Microcrystalline cellulose (MCC), prepared from natural cellulose through acid hydrolysis, has been widely used in the food, chemical and pharmaceutical industries because of its high degree of crystallinity, small particle size and other characteristics. Being different from conventional mineral acids, phosphotungstic acid (H₃PW₁₂O₄₀, HPW) was explored for hydrolyzing cellulose selectively for the preparation of MCC in this study. Various reaction parameters, such as the acid concentration, reaction time, temperature and solid-liquid ratio, were optimized. Rod-like MCC was obtained with a high yield of 93.62 % and also exhibited higher crystallinity and narrower particle diameter distribution (76.37 %, 13.77–26.17 μm) compared with the raw material (56.47 %, 32.41–49.74 μm) at 90 °C for 2 h with 58 % (w/w) HPW catalyst and a solid-liquid radio of 1:40. Furthermore, HPW can easily be extracted and recycled with diethyl ether for four runs without affecting the quality of the MCC products. The technology of protecting the crystalline region while selectively hydrolyzing the amorphous region of cellulose as much as possible by using HPW is of great significance. Due to the strong Brønsted acid sites and highest activity in solid heteropoly acid, the use of effective homogeneous HPW may offer an eco-friendly and sustainable way to selectively convert fiber resources into chemicals in the future.     

银离子修饰的介孔磷钨酸/二氧化硅催化剂氧化脱硫性能研究

采用银修饰介孔磷钨酸/二氧化硅（mesoporous HPW/SiO₂）催化剂,并研究了其在模拟柴油和真实柴油氧化脱硫反应中的催化性能。通过银修饰介孔HPW/SiO₂,结合银离子对有机硫化物的选择吸附性和HPW对有机硫化物的催化氧化活性,以达到选择氧化脱硫的目的。模拟柴油分别采用石油醚、苯、1-辛烯和二苯并噻吩配制,当银离子与HPW的摩尔比为2时,催化剂具有最高的选择催化氧化活性。采用N₂ 吸附-脱附、XRD、UV-vis和EDS表征了银修饰的介孔HPW/SiO₂催化剂,结果表明,银物种分散均匀且以Ag⁺形式存在。真实柴油的脱硫研究表明,相比介孔HPW/SiO₂催化剂,修饰的催化剂介孔Ag₂-HPW/SiO₂脱硫率提高了4.6%,初始硫含量为1800×10^-6的直馏柴油能被脱除至228×10^-6,脱硫率为87.3%。介孔Ag₂-HPW/SiO₂催化剂具有良好的再生性能,经再生处理后,Ag的损失量极少,其三次脱硫率达到84.8%。     

Palladium nanoparticles immobilized on EDTA‐modified Fe3O4@SiO2 nanospheres as an efficient and magnetically separable catalyst for Suzuki and Sonogashira cross‐coupling reactions

In this study, a novel heterogeneous palladium catalyst was synthesized by anchoring palladium onto ethylenediaminetetraacetic acid (EDTA)‐coated Fe₃O₄@SiO₂ magnetic nanocomposite and used for the Suzuki and Sonogashira cross‐coupling reactions. The properties of the magnetic catalyst were characterized by FT‐IR, XRD, TEM, FE‐SEM, DLS EDX, XPS, N₂ adsorption‐desorption isotherm analysis, TGA, VSM, elemental analysis and the loading level of Pd in catalyst was measured to be 0.51 mmol/g by ICP. The catalyst was used in Suzuki cross‐coupling reactions of various aryl halides, including less reactive chlorobenzenes with phenylboronic acid without any additive or ligand under green conditions. Furthermore, we have reported this recyclable catalytic system for Sonogashira cross‐coupling reactions of various aryl halides (I, Br, Cl) under copper and ligand‐free conditions in the presence of DMF/H₂O (1:2/v:v) as a solvent. The magnetic catalyst could also be separated by an external magnet and reused six times without any significant loss of activity.     

Fe3O4/MIL‐101(Fe) nanocomposite as an efficient and recyclable catalyst for Strecker reaction

A highly porous metal‐organic framework, MIL‐101(Fe), was prepared by a solvothermal method in the presence of amino‐modified Fe₃O₄@SiO₂ nanoparticles, in order to achieve Fe₃O₄/MIL‐101(Fe) nanocomposite, which was characterized by XRD, FT‐IR, SEM, TEM, BET, and VSM. This hybrid magnetic nanocomposite was employed as heterogeneous catalyst for α‐amino nitriles synthesis through three‐component condensation reaction of aldehydes (ketones), amines, and trimethylsilyl cyanide in EtOH, at room temperature. The recoverability and reusability was admitted for the heterogeneous magnetic catalyst; no significant reduction of catalytic activity was observed even after five consecutive reaction cycles.     

Biosynthesis of Pd/MnO2 nanocomposite using Solanum melongena plant extract and its application for the one‐pot synthesis of 5‐substituted 1H‐tetrazoles from aryl halides

In this work, for the first time, Solanum melongena plant extract was used for the green synthesis of Pd/MnO₂ nanocomposite via reduction osf Pd(II) ions to Pd(0) and their immobilization on the surface of manganese dioxide (MnO₂) nanoparticles (NPs) as an effective support. The synthesized nanocomposite were characterized by various analytical techniques such as Fourier transform infrared (FT‐IR), X‐ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy dispersive X‐ray spectroscopy (EDS) and UV–Vis spectroscopy. The catalytic activity of Pd/MnO₂ nanocomposite was used as a heterogeneous catalyst for the one‐pot synthesis of 5‐substituted 1H‐tetrazoles from aryl halides containing various electron‐donating or electron‐withdrawing groups in the presence of K ₄ [Fe (CN) ₆ ] as non‐toxic cyanide source and sodium azide. The products were obtained in good yields via a simple methodology and easy work‐up. The nanocatalyst can be recycled and reused several times with no remarkable loss of activity.     

Bio‐inspired iron/sulfur/graphene nanocomposite and its use in the catalysis of the oxygen reduction reaction at room temperature in alkaline media on a glassy carbon electrode

This work demonstrates the performance of a bio‐inspired iron/sulfur/graphene nanocomposite as a non‐platinum electrocatalyst for the oxygen reduction reaction (ORR) in an alkaline medium. The catalyst shows the most positive ORR onset potential (1.1 V vs. RHE) according to its unique structure in the alkaline medium (KOH solution, pH = 13) at low temperature (T = 298 K). The catalyst is evaluated by the rotating‐disk electrode (RDE) method under various rotating speeds (0–2,000 rpm) in the potential range ?0.02–1.18 V vs. a rechargeable hydrogen electrode (RHE). The number of transferred electrons, as one of the most important parameters, is almost constant over a wide range of potentials (0.1–0.8 V), which indicates a more efficient four‐electron pathway from O₂ to H₂O on the FePc‐S‐Gr surface. The mean size of catalyst centers are in the nanoscale (<10 nm). The estimated Tafel slope in the appropriate range is about ?110 mV per decade at low current density, and E_1/2 of FePc‐S‐Gr displays a negative shift of only 7.1 mV after 10,000 cycles.     

MnO2‐TiO2 Nanocomposite and 2‐(3,4‐Dihydroxyphenethyl) Isoindoline‐1,3‐Dione as an Electrochemical Platform for the Concurrent Determination of Cysteine,Tryptophan and Uric Acid

A novel modified carbon paste electrode (CPE) based on an MnO₂‐TiO₂ nanocomposite and 2‐(3,4 dihydroxyphenethyl) isoindoline‐1,3‐dione (DPID) as the modifier for the simultaneous analysis of cysteine (Cys), tryptophan (Trp) and uric acid (UA), as three key biochemicals present in human body. The MnO₂/TiO₂ nanocomposite was synthesized through a chemical co‐precipitation approach and the resulting electrode (MnO₂‐TiO₂/DPID/CPE) was used for studying the electrochemical oxidation of cysteine (Cys), tryptophan (Trp) and uric acid. As opposed to conventional CPEs, the oxidation peak potential of cysteine on MnO₂‐TiO₂/DPID/CPE had a 600.0 mV decrease in overpotential and could be observed at 30.0 mV, and the signals were linear from 0.025 to 200.0 μM, and a lower detection limit of 0.013 μM was reached. The MnO₂‐TiO₂/DPID/CPE was satisfactorily used for the concurrent analysis of Cys, Trp and UA in pharmaceutical and biological samples.     

Polyaniline/SiO2 Nanocomposite Catalyzed Efficient Synthesis of Quinoxaline Derivatives at Room Temperature

Polyaniline/SiO₂ nanocomposite material has been synthesized by using chemical oxidative method. Prepared catalytic material was characterized by means of transmission electron microscopy (TEM), thermal analysis (TG‐DTA), X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FT‐IR). Solvent stability for the catalyst has been screened using UV‐Visible spectroscopy. Polyaniline/SiO₂ catalyzed route has found to be an efficient and rapid protocol for the synthesis of quinoxaline derivatives by cyclocondensation of 1,2‐diketones and o‐phenylenediamines at room temperature. This protocol has several advantages such as high yield, good thermal stability, simple work up procedure, non‐toxic, clean, and easy recovery and reusability of the catalytic system.