Pillaiyar Puthiaraj

Microporous covalent triazine polymers: efficient Friedel–Crafts synthesis and adsorption/storage of CO2 and CH4

Two kinds of microporous covalent triazine-based organic polymers (MCTPs) were synthesized from inexpensive starting materials via a simple and cost effective Friedel–Crafts reaction route, and their CO2 and CH4 gas uptake capacities were investigated. The synthesized microporous materials showed high BET surface areas of 1452 (MCTP-1) and 859 m2 g−1 (MCTP-2). MCTP-1 exhibited a significant CO2 uptake capacity (204.3 mg g−1, 273 K/1 bar) with moderate CO2/N2 selectivity (15.4), whereas MCTP-2 showed a moderate CO2 uptake capacity (160.6 mg g−1, 273 K/1 bar) but exceptional CO2/N2 selectivity (68.6). MCTP-1 also exhibited substantial CO2 (497.4 mg g−1) and CH4 (85.4 mg g−1) storage capacities at 300 K and 35 bar.

Triazine-based covalent organic polymers: design, synthesis and applications in heterogeneous catalysis

Triazine-based covalent organic polymers (COPs) constructed from triazine or nitrile containing precursors via covalent bonding are becoming an important sub-class of porous organic framework materials for a range of applications. In particular, these materials have been proposed as a new catalyst or support material for a variety of liquid phase organic transformation reactions owing to their tunable porous structures with high surface area, high nitrogen contents, high stability in both organic and aqueous media, and relatively easy synthesis. This review article summarizes the current research activities devoted to the synthesis and characterization of new triazine-based COP materials, and their applications for heterogeneous catalysis aiming at fine chemicals synthesis are presented with critical comments.

Porous Covalent Triazine Polymer as a Potential Nanocargo for Cancer Therapy and Imaging.

A microporous covalent triazine polymer (CTP) network with a high surface area was synthesized via the Friedel-Crafts reaction and employed as a potential transport system for drug delivery and controlled release. The CTP was transformed to the nanoscale region by intense ultrasonication followed by filtration to yield nanoscale CTP (NCTP). This product showed excellent dispersibility in physiological solution while maintaining its chemical structure and porosity. An anticancer drug, doxorubicin (DOX), was loaded onto the NCTP through hydrophobic and π-π interactions, and its release was controlled at pH 4.8 and 7.4. The NCTP showed no toxicity toward cancer or normal cells, but the NCTP-DOX complex showed high efficacy against both types of cells in vitro. In-vitro cell imaging revealed that NCTP is a potential material for bioimaging. The potency of NCTP on cellular senescence was confirmed by the expression of senescence associated marker proteins p53 and p21. These results suggest that NCTP can be used as a new platform for drug delivery and imaging with potential applications in diagnosis and therapy.

Fabrication of Palladium Nanoparticles on Porous Aromatic Frameworks as a Sensing Platform to Detect Vanillin

Here, we report the fabrication of palladium nanoparticles on porous aromatic frameworks (Pd/PAF-6) using a facile chemical approach, which was characterized by various spectro- and electrochemical techniques. The differential pulse voltammetry (DPV) response of Pd/PAF-6 toward the vanillin (VA) sensor shows a linear relationship over concentrations (10-820 pM) and a low detection limit (2 pM). Pd/PAF-6 also exhibited good anti-interference performance toward 2-fold excess of ascorbic acid, nitrophenol, glutathione, glucose, uric acid, dopamine, ascorbic acid, 4-nitrophenol, glutathione, glucose, uric acid, dopamine, and 100-fold excess of Na(+), Mg(2+), and K(+) during the detection of VA. The developed electrochemical sensor based on Pd/PAF-6 had good reproducibility, as well as high selectivity and stability. The established sensor revealed that Pd/PAF-6 could be used to detect VA in biscuit and ice cream samples with satisfactory results.

Metal–Organic Frameworks for Catalysis

Metal–organic frameworks (MOFs) are a relatively new class of porous material, which are comprised of metal ions or clusters linked with poly-functional organic molecules. MOFs have been studied increasingly for heterogeneous catalysis applications because these hybrid materials have well-ordered tunable porous structures with exceptional textural properties and introduction of additional active sites can be carried out easily by relatively simple post-synthesis functionalization. This short review focuses on recent works on liquid phase catalytic reactions carried out over selected MOFs. The MOF membranes for catalysis and the potential of functionalized MOF materials for chiral reactions are also mentioned briefly.

Synthesis of copper nanoparticles supported on a microporous covalent triazine polymer: an efficient and reusable catalyst for O-arylation reaction

Copper nanoparticles were supported on a microporous covalent triazine polymer prepared by the Friedel–Crafts reaction (Cu@MCTP-1). The resulting material was characterized by powder X-ray diffraction, thermogravimetric analysis, N2 adsorption–desorption isotherms at 77 K, transmission electron microscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma optical emission spectroscopy, and Cu particles with an average size of 3.0 nm and a BET total surface area of ca. 1002 m2 g−1 were obtained. Cu@MCTP-1 was evaluated as a heterogeneous catalyst for the Ullmann coupling of O-arylation over a series of aryl halides and phenols without employing expensive ligands or inert atmosphere, which produced an excellent yield of the corresponding diaryl ethers. The catalyst could be recovered by simple centrifugation and was reusable at least five times with only a slight decrease in catalytic activity.

Electrorheological response of microporous covalent triazine-based polymeric particles

Microporous covalent triazine-based polymer (MCTP) particles were synthesized via a Friedel–Crafts reaction catalyzed by AlCl3, and their morphology and textural properties were confirmed by scanning electron microscopy and N2 adsorption isotherms, respectively. Electrorheological (ER) behavior of the MCTP particle-based ER fluid dispersed in silicone oil at a volume fraction of 5% was examined using a rotational rheometer to examine its viscoelastic properties such as shear stress, shear viscosity, yield stress, and dynamic moduli. Typical ER characteristics showed an increase with increased applied electric field strength following a polarization mechanism with the slope of 2 of the electric field-dependent yield stress, highlighting MCTP as a potential ER material. The dielectric spectra were also correlated with its ER effects using an LCR meter.

Cycloaddition of CO2 and epoxides over a porous covalent triazine-based polymer incorporated with Fe3O4

A highly porous quaterphenyl-containing covalent triazine polymer (QP-CTP) incorporated with iron oxide nanoparticles (Fe3O4@QP-CTP) was synthesized and applied as a catalyst for the cycloaddition of CO2 and epoxides under mild conditions. The synthesized materials were characterized using X-ray powder diffraction, N2 adsorption–desorption isotherm, X-ray photoelectron spectroscopy, transmission electron microscopy, and elemental analysis. The Fe3O4@QP-CTP composite in the presence of tetrabutylammonium bromide showed 95% conversion of epoxides with high selectivity to cyclic carbonates at 50 °C, 0.1 MPa CO2 in 12 h. The reaction kinetics was further improved upon increasing the temperature to 80 °C. The catalyst was easily recovered using a magnet, and its stability was confirmed using a recycle test, which showed that the catalyst could be re-used for a minimum of eight consecutive runs without a noticeable decline in catalytic activity. A plausible mechanistic pathway of the cycloaddition reaction over Fe3O4@QP-CTP was also proposed.

Photoluminescent AuNCs@UiO-66 for Ultrasensitive Detection of Mercury in Water Samples

In this work, we synthesized gold nanoclusters within a Zirconium-based metal–organic framework (AuNCs@UiO-66) that may create new prospects for the development of novel sensing materials for biosensor applications. The resulting AuNCs@UiO-66 nanocomposite exhibits red fluorescence with a high quantum yield (11%), and the AuNCs are homogeneously distributed along UiO-66. Analytical and morphological characterizations of the resulting material were carried out by UV–visible spectroscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy. The synthesized AuNCs@UiO-66 nanocomposite was used for the effective detection of Hg2+ ions with a detection limit as low as 77 pM. Moreover, the fabricated sensors also successfully detected Hg2+ in real water samples. This sensor is stable and highly fluorescent, developed using a simple fabrication method, and would be constructive for the detection of other metal ions and in biological applications.