Pd nanoparticles on a dual acid-functionalized porous polymer for direct synthesis of H2O2: Contribution by enhanced H2 storage capacity

Pillaiyar Puthiaraj,Kwangsun Yu,Wha-Seung Ahn,정영민 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.81 No.-

Direct synthesis of H2O2 from H2 and O2 can avoid the energy and environmental problems of currentmulti-step anthraquinone oxidation process by enabling high atom utilization and generating only awater by-product. However, the direct process suffers a low H2O2 yield, and it is challenging to suppressthe unfavorable side-reactions in the absence of corrosive additives under the restriction of explosionlimits. In this study, an efficient new catalyst was prepared by immobilizing Pd nanoparticles (NPs) on anacidic hyper-crosslinked porous polymer (HCPP). The Pd catalyst supported on HCPP functionalized withboth carboxylic and sulfonic acids (Pd/c-s-HCPP) achieved as high as 3130 mmol H2O2/g Pd.h with 82%selectivity to H2O2, which corresponded to one of the best catalysts reported so far. Pd/c-s-HCPP showedsuperior catalytic performance when compared with ones by Pd NPs supported on unfunctionalizedHCPP (Pd/HCPP), or sulfonated resin (Pd/SO3H-resin). Extensive characterizations and H2 adsorptionmeasurements indicated that the c-s-HCPP provided (i) selective adsorption sites for Pd precursors, (ii)acted as an efficient H2 reservoir in the proximity of the small Pd NPs formed, and (iii) imparts solidacidity to enhance H2O2 selectivity, which offered a new direction in the catalyst design for the directsynthesis of H2O2.

An Overview of Severe Acute Respiratory Syndrome-Coronavirus (SARS-CoV) 3CL Protease Inhibitors: Peptidomimetics and Small Molecule Chemotherapy

Pillaiyar, Thanigaimalai,Manickam, Manoj,Namasivayam, Vigneshwaran,Hayashi, Yoshio,Jung, Sang-Hun American Chemical Society 2016 Journal of medicinal chemistry Vol.59 No.14

<P>Severe acute respiratory syndrome (SARS) is caused by a newly emerged coronavirus that infected more than 8000 individuals and resulted in more than 800 (10-15%) fatalities in 2003. The causative agent of SARS has been identified as a novel human coronavirus (SARS-CoV), and its viral protease, SARS-CoV 3CL<SUP>pro</SUP>, has been shown to be essential for replication and has hence been recognized as a potent drug target for SARS infection. Currently, there is no effective treatment for this epidemic despite the intensive research that has been undertaken since 2003 (over 3500 publications). This perspective focuses on the status of various efficacious anti-SARS-CoV 3CL<SUP>pro</SUP> chemotherapies discovered during the last 12 years (2003-2015) from all sources, including laboratory synthetic methods, natural products, and virtual screening. We describe here mainly peptidomimetic and small molecule inhibitors of SARS-CoV 3CL<SUP>pro</SUP>. Attempts have been made to provide a complete description of the structural features and binding modes of these inhibitors under many conditions.</P> [FIG OMISSION]</BR>

Inhibitors of Melanogenesis: An Updated Review

Pillaiyar, Thanigaimalai,Namasivayam, Vigneshwaran,Manickam, Manoj,Jung, Sang-Hun American Chemical Society 2018 Journal of medicinal chemistry Vol.61 No.17

<P>Melanins are pigment molecules that determine the skin, eye, and hair color of the human subject to its amount, quality, and distribution. Melanocytes synthesize melanin and provide epidermal protection from various stimuli, such as harmful ultraviolet radiation, through the complex process called melanogenesis. However, serious dermatological problems occur when there is excessive production of melanin in different parts of the human body. These include freckles, melasma, senile lentigo, pigmented acne scars, and cancer. Therefore, controlling the production of melanin is an important approach for the treatment of pigmentation related disorderes. In this Perspective, we focus on the inhibitors of melanogenesis that directly/indirectly target a key enzyme tyrosinase as well as its associated signaling pathways.</P> [FIG OMISSION]</BR>

Downregulation of melanogenesis: drug discovery and therapeutic options

Pillaiyar, Thanigaimalai,Manickam, Manoj,Jung, Sang-Hun Elsevier 2017 DRUG DISCOVERY TODAY Vol.22 No.2

<P>Melanin, primarily responsible in humans for hair, eye and skin pigmentation, is produced by melanocytes through a process called melanogenesis. However, the abnormal accumulation of melanin causes dermatological problems such as cafe-au-lait macules ephelides (freckles), solar lentigo (age spots) and melasma, as well as cancer and vitiligo. Hence the regulation of melanogenesis is very important for treating hyperpigmentary disorders. Numerous antimelanogenic agents that target tyrosinase activity and/or stability, melanosome maturation, transfer and trafficking, or melanogenesis-related signaling pathways have been developed. This article reviews recent advances in research and development of human tyrosinase and melanogenesis-related signaling pathway inhibitors. Attempts have been made to provide a complete description of the mechanism of action of inhibitors on various melanogenesis signaling pathways.</P>

Dual-functionalized porous organic polymer as reusable catalyst for one-pot cascade C C bond-forming reactions

Puthiaraj, Pillaiyar,Chung, Young-Min,Ahn, Wha-Seung Elsevier 2017 Molecular catalysis Vol.441 No.-

<P>A porous dual-functional acid-base covalent organic polymer catalyst (CBAP-1(EDA-SO3H)) was prepared using a facile Friedel-Crafts reaction of triphenylbenzene and terephthaloyl chloride to prepare the polymer backbone (CBAP-1) followed by functionalization with ethylenediamine (EDA) and a simple chlorosulfonic acid treatment. The resultant polymeric catalyst and its functional moieties were characterized by Fourier transform infrared (FTIR), elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), and N-2 adsorption-desorption isotherm analyses. The catalytic activity of CBAP-1(EDA-SO3H) was then assessed for one-pot cascade C-C bond-forming reactions involving deacetylation-Knoevenagel condensation and Henry reactions. Compared with the homogeneous catalyst and CBAP-1 functionalized with just acid or base, CBAP-1(EDA-SO3H) showed superior catalytic activity and selectivity, and was found to be reusable for up to seven consecutive runs. A catalytic mechanism for C-C bond-forming reactions over CBAP-1(EDA-SO3H) was proposed. (C) 2017 Elsevier B.V. All rights reserved.</P>

Microporous amine-functionalized aromatic polymers and their carbonized products for CO₂ adsorption

Puthiaraj, Pillaiyar,Lee, Yu-Ri,Ahn, Wha-Seung Elsevier 2017 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.319 No.-

<P><B>Abstract</B></P> <P>Two porous aromatic polymers incorporated with carbonyl-functionality (CBAP-1 and CBAP-2) were synthesized via a Friedel-Crafts benzoylation reaction between 1,3,5-triphenylbenzene/biphenyl and terephthaloyl chloride/1,3,5-benzenetricarbonyl trichloride in the presence of anhydrous AlCl<SUB>3</SUB> as catalyst, and post-synthetically functionalized with ethylenediamine to obtain CBAP-1(EDA) and CBAP-2(EDA). The microporous carbon materials with BET surface areas up to 1063m<SUP>2</SUP> g<SUP>−1</SUP> were also prepared by carbonization of CBAP-1 and CBAP-1(EDA). After characterization using various analytical methods, these materials were tested as adsorbents for CO<SUB>2</SUB> and CH<SUB>4</SUB> capture at ambient conditions. High CO<SUB>2</SUB>/N<SUB>2</SUB> (97.2 and 87.8) and CO<SUB>2</SUB>/CH<SUB>4</SUB> (24.3 and 22.3) selectivities were observed for CBAP-1(EDA) and CBAP-2(EDA), respectively, at 273K/1bar, whereas the carbonized microporous materials exhibited high adsorption capacities for CO<SUB>2</SUB> (216.0–231.6mgg<SUP>−1</SUP>) and CH<SUB>4</SUB> (36.6–38.1mgg<SUP>−1</SUP>). This work demonstrates that post-synthesis functionalization of a porous aromatic polymer prepared by the simple Friedel-Crafts reaction can be an effective means to produce a family of host materials for effective gas adsorption.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cost-effective carbonyl-incorporated aromatic polymers (CBAPs) were synthesized. </LI> <LI> CBAPs were functionalized with ethylenediamine to obtain CBAPs (EDA). </LI> <LI> Microporous carbons were also prepared by carbonization of CBAPs and CBAPs (EDA). </LI> <LI> Prepared carbon materials exhibited high adsorption capacities for CO<SUB>2</SUB> and CH<SUB>4</SUB>. </LI> <LI> High CO<SUB>2</SUB> selectivities over N<SUB>2</SUB> and CH<SUB>4</SUB> were observed for CBAPs (EDA). </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Facile synthesis of microporous carbonaceous materials derived from a covalent triazine polymer for CO2 capture

Puthiaraj, Pillaiyar,Ahn, Wha-Seung Elsevier Inc 2017 Journal of Energy Chemistry Vol.26 No.5

Ullmann coupling of aryl chlorides in water catalyzed by palladium nanoparticles supported on amine-grafted porous aromatic polymer

Puthiaraj, Pillaiyar,Ahn, Wha-Seung Elsevier 2017 Molecular catalysis Vol.437 No.-

<P>A chemically stable porous carbonyl-incorporated aromatic polymer (CBAP-1(EDA)) was post synthetically functionalized with ethylenediamine, and used as a solid support to immobilize the Pd nanoparticles (Pd@CBAP-1(EDA)) with particle size of 2-4 nm using conventional chemical reduction. The synthesized Pd@CBAP-1(EDA) was characterized by powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), transmission electron spectroscopy (TEM), thermogravimetric analysis (TGA), N-2 adsorption-desorption isotherms, and inductively coupled plasma optical emission spectrometry (ICP-OES). The obtained material was tested as a solid catalyst for the environmentally-benign Ullmann self-coupling of aryl chlorides in water medium, showing excellent catalytic performance for a series of aryl chlorides without the addition of any external additives. The catalyst was easily recovered by simple filtration and could be reused six times without loss of its initial activity. The high catalyst stability was confirmed by hot filtration and ICP analysis. (C) 2017 Elsevier B.V. All rights reserved.</P>

CO₂ Capture by Porous Hyper-Cross-Linked Aromatic Polymers Synthesized Using Tetrahedral Precursors

Puthiaraj, Pillaiyar,Ahn, Wha-Seung American Chemical Society 2016 INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH - Vol.55 No.29

<P>Low-cost synthesis of porous hyper-cross-linked aromatic polymers (PHAPs) was achieved via the FeCl3-catalyzed Friedel-Crafts alkylation reaction between tetraphenylsilane or tetraphenylgermanium as a building block and formaldehyde dimethylacetal as a cross-linker. The synthesized polymers were chemically and thermally stable and exhibited high surface areas of up to 1137 m(2) (PHAP-1) and 1059 m(2) g(-1) (PHAP-2). The adsorption isotherms of the PHAPs revealed a high CO2 adsorption capacity (104.3-114.4 mg g(-1)) with an isosteric heat of adsorption in the range 26.5-27.3 kJ mol(-1) and a moderate CH4 adsorption capacity (12.6-13.8 mg g(-1)) at 273 K and 1 bar. The PHAP networks also exhibited high CO2/N-2 and CO2/CH4 relativities of 29.3-34.2 and 11.3-12.5, respectively, at 273 K.</P>

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

Puthiaraj, Pillaiyar,Cho, Sung-Min,Lee, Yu-Ri,Ahn, Wha-Seung The Royal Society of Chemistry 2015 Journal of Materials Chemistry A Vol.3 No.13

<▼1><P>Microporous covalent triazine polymers were synthesized from inexpensive starting materials and their CO2 and CH4 gas uptakes were investigated.</P></▼1><▼2><P>Two kinds of microporous covalent triazine-based organic polymers (MCTPs) were synthesized from inexpensive starting materials <I>via</I> 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 m<SUP>2</SUP> g<SUP>−1</SUP> (MCTP-2). MCTP-1 exhibited a significant CO2 uptake capacity (204.3 mg g<SUP>−1</SUP>, 273 K/1 bar) with moderate CO2/N2 selectivity (15.4), whereas MCTP-2 showed a moderate CO2 uptake capacity (160.6 mg g<SUP>−1</SUP>, 273 K/1 bar) but exceptional CO2/N2 selectivity (68.6). MCTP-1 also exhibited substantial CO2 (497.4 mg g<SUP>−1</SUP>) and CH4 (85.4 mg g<SUP>−1</SUP>) storage capacities at 300 K and 35 bar.</P></▼2>