High-throughput Acid-Base Tandem Organocatalysis over Hollow Tube-Shaped Porous Polymers and Carbons

Mesoporous Porphyrin-Silica Nanocomposite as Solid Acid Catalyst for High Yield Synthesis of HMF in Water

Solid acid catalysts occupy a special class in heterogeneous catalysis for their efficiency in eco-friendly conversion of biomass into demanding chemicals. We synthesized porphyrin containing porous organic polymers (PorPOPs) using colloidal silica as a support. Post-modification with chlorosulfonic acid enabled sulfonic acid functionalization, and the resulting material (PorPOPS) showed excellent activity and durability for the conversion of fructose to 5-hydroxymethyl furfural (HMF) in green solvent water. PorPOPS composite was characterized by N2 sorption, FTIR, TGA, CHNS, FESEM, TEM and XPS techniques, justifying the successful synthesis of organic networks and the grafting of sulfonic acid sites (5 wt%). Furthermore, a high surface area (260 m2/g) and the presence of distinct mesopores of ~15 nm were distinctly different from the porphyrin containing sulfonated porous organic polymer (FePOP-1S). Surprisingly the hybrid PorPOPS showed an excellent yield of HMF (85%) and high selectivity (>90%) in water as compared to microporous pristine-FePOP-1S (yield of HMF = 35%). This research demonstrates the requirement of organic modification on silica surfaces to tailor the activity and selectivity of the catalysts. We foresee that this research may inspire further applications of biomass conversion in water in future environmental research.

Metal-Organic Polymer-Derived Interconnected Fe-Ni Alloy by Carbon Nanotubes as an Advanced Design of Urea Oxidation Catalysts

The electrochemical urea oxidation reaction (UOR) is considered as a promising renewable source for harvesting energy from waste. We report a new synthetic design approach to produce an iron-nickel alloy nanocatalyst from a metal-organic polymer (MOP) by a single-step carbonization process at 500 °C, thus forming a core-shell of iron-nickel-coated carbon (C@FeNi) nanostructures wired by embedded carbon nanotubes (CNTs) (CNT/C@FeNi). Powder X-ray diffraction confirmed the formation of metallic FeNi₃ alloy nanoparticles (∼20 to 28 nm). Our experimental results showed that MOP containing CNTs acquired an interconnected hierarchical topology, which prevented the collapse of its microstructure during pyrolysis. Hence, CNT/C@FeNi shows higher porosity (10 times) than C@FeNi. The electrochemical UOR in alkaline electrolytes on these catalysts was studied using cyclic voltammetry (CV). The result showed a higher anodic current (3.5 mA cm^-2) for CNT/C@FeNi than for C@FeNi (1.1 mA cm^-2) at 1.5 V/RHE. CNT/C@FeNi displayed good stability in chronoamperometry experiments and a lower Tafel slope (33 mV dec^-1) than C@FeNi (41.1 mV dec^-1). In this study, CNT/C@FeNi exhibits higher exchange current density (3.2 μA cm^-2) than does C@FeNi (2 μA cm^-2). The reaction rate orders of CNT/C@FeNi and C@FeNi at a kinetically controlled potential of 1.4 V/RHE were 0.5 and 0.9, respectively, higher than the 0.26 of β-Ni(OH)₂, Ni/Ni(OH)₂ electrodes. The electrochemical impedance result showed a lower charge-transfer resistance for CNT/C@FeNi (61 Ω·cm^-2) than for C@FeNi (162 Ω·cm^-2), due to faster oxidation kinetics associated with the CNT linkage. Moreover, CNT/C@FeNi exhibited a lower Tafel slope and resistance and higher heterogeneity (25.2 × 10^-5 cm s^-1), as well as relatively high faradic efficiency (68.4%) compared to C@FeNi (56%). Thus, the carbon-coated FeNi₃ core connected by CNT facilitates lower charge-transfer resistance and reduces the UOR overpotential.

Early detection of leptospirosis using Anti-LipL32 carbon nanotube immunofluorescence probe

Leptospirosis is a widespread zoonosis and an emerging public health problem. Leptospirosis symptoms are often confused or misdiagnosed with other febrile illness like malaria, viral hepatitis, influenza, dengue, typhoid, melioidosis, and scrub typhus as the clinical manifestations are almost similar. Therefore, early and accurate diagnosis of leptospirosis is indeed critical for proper and prompt treatment. Herein, we report the development of single-walled carbon nanotubes based immunofluorescence probe (Carbo-Lip) for the detection of leptospirosis at an early phase by utilising major outer membrane protein, LipL32 of Leptospira. The Carbo-Lip probe was fabricated through immuno recognition method with fluorescent dye functionalized LipL32 monoclonal antibodies (mAbs), secondary antibody and Leptospira. Surface characterization studies such as Fourier transform infrared spectroscopy with the attenuated total reflectance, scanning electron microscopy, transmission electron microscopy, Zeta potential, and X-ray photoelectron spectroscopy techniques were used to demonstrate the successful fabrication of Carbo-Lip probe. The sensor probe was capable of detecting the presence of leptospires at a lower concentration of 10³/ml, and could detect 10² leptospires in 100 μL of sample within 3 h of the test conditions, and was stable up to 2 weeks. This Carbo-Lip probe was further tested and validated for its capacity to detect Leptospira in clinical samples, which exhibited high selectivity and specificity towards Leptospira even in the presence of malaria and dengue. Our results were consistent with microscopic agglutination test, which is known as gold standard, immunoglobulin M (IgM) enzyme-linked immunoassay (ELISA), IgM spot test, and culture tests for the diagnosis of Leptospira infection.

Thiophene containing microporous and mesoporous nanoplates for separation of mercury from aqueous solution

Thiophene-based novel porous polymeric nanoplates synthesized through a template free approach show high mercury capture efficiency from contaminated water and may be promising for environmental applications.

Microporous Nanotubes and Nanospheres with Iron-Catechol Sites: Efficient Lewis Acid Catalyst and Support for Ag Nanoparticles in CO2 Fixation Reaction

Fe^III -containing hyper-crosslinked microporous nanotubes (FeNTs) and nanospheres (FeNSs) are synthesized through the reaction of catechol and dimethoxymethane in the presence of FeCl₃ or CF₃ SO₃ H. Both FeNTs and FeNSs demonstrate excellent catalytic activity in Lewis acid catalysis (hydrolysis and regioselective methanolysis of styrene oxide) and tandem catalysis involving a sequential oxidation-cyclization process, which selectively converts benzyl alcohol to 2-phenyl benzimidazole. Apart from Lewis acidity, the FeNTs and FeNSs also showed CO₂ uptake capacities of 2.6 and 2.2 mmol g^-1 , respectively, at a pressure of 1 atm and temperature of 273 K. Furthermore, Ag nanoparticles are immobilized successfully on the surfaces of FeNTs and FeNSs by the liquid-phase impregnation method to prepare Ag@FeNT and Ag@FeNS nanocomposites, which show high catalytic activity for the selective fixation of CO₂ to phenylacetylene to yield phenylpropiolic acid at 60 °C and 1 atm CO₂ pressure. Hence, Fe^III -catechol-containing hyper-crosslinked nanotubes and nanospheres have huge potential not only as Lewis acid catalysts, but also as excellent supports for immobilizing Ag nanoparticles in the design of a robust catalyst for the carboxylation of terminal alkynes, which has wide scope in catalysis and environmental research.

Control Synthesis of Tubular Hyper-Cross-Linked Polymers for Highly Porous Carbon Nanotubes

Porous carbon nanotubes (PCNTs) have attracted considerable attention due to their large specific surface areas and unique one-dimensional (1D) structures. However, most of the reported synthetic strategies for PCNTs are complex and expensive. Herein, we present a self-templated, surfactant-free strategy for the synthesis of high-quality PCNTs with high surface area by direct carbonization of 1D hyper-cross-linked polymer nanotubes. The precursors of the 1D hyper-cross-linked polymer nanotubes were synthesized by FeCl₃ catalyzed Friedel-Crafts alkylation of aromatic hydrocarbons with formaldehyde dimethyl acetal. It was found that the monomer concentration and mechanical agitation play crucial roles in the formation of the 1D tubular hyper-cross-linked polymer precursor. The tube size of the resulting PCNTs could be finely controlled by the aromatic monomers with different molecular sizes. The excellent electrochemical performances of the supercapacitors fabricated from the PCNTs demonstrate that these PCNTs are promising for the electrode materials of high-performance supercapacitors. This work highlights that the facile synthetic strategy for PCNTs would open up new avenues of porous carbon nanotube materials with promising applications.