Piyali Bhanja

Pd Nanoparticles Decorated on Hypercrosslinked Microporous Polymer: A Highly Efficient Catalyst for the Formylation of Amines through Carbon Dioxide Fixation

CO2 fixation reaction is one of the most challenging chemical transformations not only in the context of environmental remediation but also for effective utilization of abundant carbon sources in nature. Here, we have stabilized palladium nanoparticles (NPs) at the surfaces of a hypercrosslinked porous polymer bearing carbazole and α,α′‐dibromo‐p‐xylene monomeric units to obtain a Pd@HMP‐1 nanocatalyst. The material has been thoroughly characterized by powder XRD, high‐resolution (HR)‐TEM, field‐emission (FE)‐SEM, Brunauer–Emmett–Teller (BET), thermogravimetric (TGA), and FTIR analysis. Pd@HMP‐1 showed excellent catalytic activity towards formylation of amines by carbon dioxide fixation under mild reaction conditions. The high surface area and nitrogen‐rich porous surface make the polymer a suitable support for the palladium nanoparticles and endow it with high recycling efficiency in this CO2 fixation reaction.

A New Triazine-Based Covalent Organic Framework for High-Performance Capacitive Energy Storage

The new covalent organic framework material TDFP-1 was prepared through a solvothermal Schiff base condensation reaction of the monomers 1,3,5-tris-(4-aminophenyl)triazine and 2,6-diformyl-4-methylphenol. Owing to its high specific surface area of 651 m2  g-1 , extended π conjugation, and inherent microporosity, TDFP-1 exhibited an excellent energy-storage capacity with a maximum specific capacitance of 354 F g-1 at a scan rate of 2 mV s-1 and good cyclic stability with 95 % retention of its initial specific capacitance after 1000 cycles at 10 A g-1 . The π-conjugated polymeric framework as well as ionic conductivity owing to the possibility of ion conduction inside the micropores of approximately 1.5 nm make polymeric TDFP-1 a favorable candidate as a supercapacitor electrode material. The electrochemical properties of this electrode material were measured through cyclic voltammetry, galvanic charge-discharge, and electrochemical impedance spectroscopy, and the results indicate its potential for application in energy-storage devices.

Organic–Inorganic Hybrid Metal Phosphonates as Recyclable Heterogeneous Catalysts

Successful incorporation of a suitable organic moiety in a porous inorganic metal phosphate network can not only make the corresponding organic–inorganic framework more flexible and robust, but it introduces more hydrophobicity at the surface of the resulting nanostructured material, which is highly desirable for their catalytic application in liquid‐phase chemical transformations. Following the success of organic–inorganic hybrid mesoporous silicas, a wide range of analogous hybrid metal phosphonates have been designed. This has opened up a wide diversity of open framework porous nanomaterials, which show excellent catalytic activities in many organic transformations that are not possible with their corresponding inorganic counterparts. Here, we have summarized the recent developments in designing organic–inorganic hybrid porous metal phosphonates in this brief review with a special emphasis on their catalytic potential in liquid‐phase organic transformations.

Rapid template-free synthesis of an air-stable hierarchical copper nanoassembly and its use as a reusable catalyst for 4-nitrophenol reduction

A hierarchical copper nanoassembly was synthesized by one-pot solvothermal treatment at 150 °C for 2 h in the presence of copper nitrate, formamide and water. The product exhibited phase pure hierarchical Cu microspheroids (2–7 μm) comprising a nanorod (50–100 nm) assembly. The Cu microspheroids showed excellent air-stability, antioxidative properties and catalytic reduction of p-nitrophenol.

Micelle-templated synthesis of Pt hollow nanospheres for catalytic hydrogen evolution

As an alternative to galvanic replacement reactions and hard-template strategies, we report an efficient, mild and simple synthesis strategy for fabrication of colloidal platinum (Pt) hollow nanospheres. An aqueous asymmetric triblock copolymer poly(styrene-b-vinyl-2-pyridine-b-ethylene oxide) [PS(20.1k)–PVP(14.2k)–PEO(26.0)] micelle with core–shell–corona architecture has been found to be an efficient soft scaffold for the synthesis of Pt hollow nanospheres using K2PtCl6 as a metal precursor and NaBH4 as a reducing agent. In the core–shell–corona type micelles, the core serves as a template for void volume creation, the shell domain acts reaction site for inorganic precursors, and the corona stabilizes the composite particles. The polymer/Pt composite particles were solvent-extracted by refluxing with dimethyl formamide (DMF) at 160 °C to remove polymeric materials and obtain hollow particles. Investigation of precursor concentrations suggested that the wall-structures become irregular and uneven as the molar ratio of PVP/Pt(IV) increases from 1 : 12 to 1 : 25, whereas the use of polymers with large PS block length [PS(45k)–PVP(16k)–PEO(8.5)] results in the formation of spherical particles with slightly increased hollow void-space diameters. The polymeric micelles and Pt hollow nanospheres were thoroughly characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), infra-red (FT IR), thermal (TG/DTA) and nitrogen sorption analyses. The catalytic activity of the Pt hollow nanospheres was investigated for hydrogen liberation from ammonia–borane (AB) by hydrolysis reaction at room temperature. The catalytic activity of the Pt hollow nanospheres reveals that they can serve as a promising heterogeneous catalyst towards hydrogen generation system using AB as solid hydrogen storage materials.

Triazine-Based Porous Organic Polymer with Good CO2 Gas Adsorption Properties and an Efficient Organocatalyst for the One-Pot Multicomponent Condensation Reaction

A new porous organic polymer PDVBTT‐1 (poly‐divinylbenzene‐co‐triallyloxytriazine) has been synthesized through radical co‐polymerization utilizing two monomers, that is, divinylbenzene and 2,4,6‐triallyloxy‐1,3,5‐triazine in the presence of AIBN (azobisisobutyronitrile) as a radical initiator under solvothermal conditions in the absence of any structure directing agent. The polymer has been characterized thoroughly by N2 sorption, FTIR, UV/Vis, and solid‐state 13C cross‐polarization magic angle spinning (CP MAS) NMR spectroscopy, field emission FE‐SEM, high‐resolution HR‐TEM, and thermogravimetric/differential thermal analysis (TG/DTA). Owing to the considerably good surface area of 644 m2 g−1 and surface basic sites (1.10 mmol g−1), the material showed very good CO2 adsorption properties. Furthermore, the porous polymer showed good catalytic activity in the base‐catalyzed, one‐pot, multicomponent condensation reaction between various substituted aromatic aldehydes, malononitrile, and activated phenols such as 2‐naphthol, resorcinol, etc., for the synthesis of 2‐amino‐chromenes in water and under solvent‐free microwave irradiation conditions. This N‐rich porous polymer is highly recyclable and thus it has potential for a wide range of base‐catalyzed organic transformations in the future.

Silver nanoparticles supported over mesoporous alumina as an efficient nanocatalyst for N-alkylation of hetero (aromatic) amines and aromatic amines using alcohols as alkylating agent.

We have successfully embedded rhombohedral crystallites of silver nanoparticles (Ag-NPs) over mesoporous alumina (Ag@Al2O3) material for the first time. The Ag@Al2O3 has been characterized by powder X-ray diffraction (PXRD), ultra high resolution transmission electron microscopy (UHR-TEM), scanning electron microscopy (SEM), N2 adsorption/desorption isotherm, Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible absorption spectra (UV-Vis), and thermogravimetric analysis (TGA). The PXRD confirms the presence of the rhombohedral phase of Ag nanoparticles. The agglomeration of the silver nanoparticle having a dimension of 80-90nmhas been clearly observed from UHR-TEM images. This novel nanocatalyst showed excellent catalytic activity towards the N-alkylation of hetero (aromatic) amines and aromatic amines using alcohols as the alkylating agent. The catalyst is heterogeneous in nature and can be recovered and recycled more than five reaction cycles without any noticeable loss in its catalytic activity.

An efficient mesoporous carbon nitride (g-C3N4) functionalized Pd catalyst for carbon–carbon bond formation reactions

Metal nanoparticles in pristine form without any stabilizing agents and free from agglomeration are very critical for their function and diverse catalytic applications. With the goal to accomplish a molecularly defined Pd-based heterogeneous C–C bond forming catalyst, highly ordered mesoporous nitrogen-rich carbon nitride (MCN) polymers with extended three-dimensional π-conjugation have been used as solid supports. Here, palladium nanoparticles ca. Pd(II) and Pd(0) were dispersed onto MCN and used in a surface-exposed state that renders them with inherently high catalytic activity. The catalysts were thoroughly investigated by a series of characterization techniques such as small-angle XRD, TEM, EDAX, SEM, 13C MAS NMR, 1H NMR, FTIR, N2 sorption, and CHN analyses. The XRD, N2 sorption isotherms and TEM show that Pd-catalysts maintain a hexagonal mesoporous structure with a high surface area (355.9 m2 g−1) and pore volume of 0.63 mL g−1. 13C MAS NMR and FTIR spectroscopy confirmed the presence of triazine ring, NH2 and NH groups in the polymeric graphitic carbon nitrides. Both Pd(II) and Pd(0) catalysts exhibited good catalytic activities and product selectivities in the copper- and phosphine-free Sonogashira cross-coupling reaction between aryl iodide and aryl alkynes. Hot filtration tests confirmed the heterogeneity of the catalysts and the catalysts were reused for six successive reactions with negligible change in the conversion.

N-rich porous organic polymer with suitable donor–donor–acceptor functionality for the sensing of nucleic acid bases and CO2 storage application

A new high surface area porous organic polymer PDVTD-1 (poly-divinylbenzene-co-tartardiamide) has been synthesized via radical copolymerization of divinylbenzene and (+)-N,N′-diallyltartardiamide using AIBN initiator under solvothermal conditions. A detailed characterization of this functionalized porous polymer is performed using N2 sorption, solid state 13C CP MAS NMR, FT-IR and UV-Vis spectroscopy, HR-TEM, FE-SEM, TGA/DTA and CHN analysis. Photoluminescence study of the material is carried out to investigate the sensing behaviour of PDVTD-1 towards different nucleic acid bases. It is observed that at very low concentration of base (i.e. 10−6 to 10−7 M) PDVTD-1 can selectively sense cytosine, whereas in the concentration range 10−3 to 10−5 M adenine, thymine and uracil also shows quenching of its fluorescence intensity. Moreover, this N-rich porous polymer PDVTD-1 showed excellent CO2 uptake capacity of 8.76 mmol g−1 (38.54 wt%) at 273 K and 3 bar pressure with an initial isosteric heat of adsorption (Qst) of 72 kJ mol−1.

Chiral Co(III)–salen complex supported over highly ordered functionalized mesoporous silica for enantioselective aminolysis of racemic epoxides

Here we demonstrate the synthesis of a novel chiral Co(III)–salen complex supported functionalized 2D-hexagonal mesoporous silica material Co(III)@AFS-1. This material has shown excellent catalytic activity for the regio- and enantioselective asymmetric ring opening (ARO) of terminal and meso epoxides using various aromatic as well as cyclic amines to produce chiral β-amino alcohols having very good enantioselectivities (ee > 99%) at ambient temperature under solvent-free neat conditions.