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Synthesis of cyclic carbonates via CO2 cycloaddition reaction with epoxides is one of the promising strategies to valorize greenhouse gas CO2, thereby fixing it to the value-added chemicals. In this study, uniform copper oxide nanoparticles (Cu2O, Cu4O3) with variable oxidation states are stabilized by functionalized covalent organic frameworks (COF) and effectively utilized as a catalyst for the synthesis of cyclic carbonates under ambient temperature and atmospheric pressure. Characterization techniques e.g. powdered X-ray Diffraction (PXRD), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FT-IR) and nitrogen physisorption (BET) coupled with DFT studies predict that the copper oxide nanoparticles are anchored on the mesochannels of covalent organic frameworks through a covalent-coordinate linkage. The catalyst exhibits significantly high turn over numbers (TON, order of 105) and more than 99% selectivity towards synthesis of cyclic carbonates with exceptional recyclability.

Understanding the effects of silicate concentration of activator solution is critical for developing cost effective geopolymeric binders, and controlling their setting and hardening behavior. However, in calcium containing geopolymers, effects of silicate concentration of activator solution on the amount and nature of reaction products at different ages are still unclear. In this study, we examined class F fly ash and slag binders activated by both silicate and hydroxide solutions. Faster hardening from ultrasonic wave reflection and faster reaction from calorimetry were seen in the binder activated by silicates than that by hydroxides. Subtraction of infrared spectra, aided by selective chemical treatments, indicated the main reaction peak in calorimetry curves correlates with formation of calcium silicate hydrate/calcium aluminosilicate hydrate (C-S-H/C-A-S-H) of the same Ca/Si ratio in the hydroxide activated binder but formation of both C-S-H gel and potassium aluminosilicate hydrate (K-A-S-H) gel in the silicate activated binder. In additional tests, the main reaction peak of the silicate activated binder was delayed as silicates in the activator solution became less polymerized, further confirming contribution of K-A-S-H formation towards the main heat peak in calorimetry curve. Scanning electron micrographs showed products grew from surface into pore space in the hydroxide activated binder but within interstitial space in the silicate activated binder.

A polystyrene functionalized Zinc anthranilic acid complex catalyst has been prepared. The PS-Zn-anthra complex has been characterized by EDX, Scanning electron micrographs (FE-SEM), FTIR spectra, UV–vis spectra and thermogravimetric analyses. A greener and novel methodology was considered for the production of dicoumarol derivatives utilizing PS-Zn-anthra complex as a Lewis acid catalyst, non-toxic, mild in H2O employing heteroaromatic/aromatic aldehydes and 4-hydroxycoumarin. The catalyst also shows good catalytic activity in the cyclo addition of CO2 to epoxide. The results of activity of catalyst imply that the procedure adopted provides numerous advantages such as low loading of catalyst, operational simplicity, mild reaction conditions, quantitative yields, and short reaction time. The PS-Zn-anthra complex exhibited the elevated efficiency of recycling in these reactions. This catalyst can be recycled for five times without appreciable loss of its activity.

Structure-property relationships of alkali-activated aluminosilicate gels are studied using rheology, neutron scattering, solid-state NMR, and TEM to develop a pseudo-ternary state diagram. Empirical gel states are classified by the rheological behavior (sol-gel transition and scaling of storage modulus with aluminum concentration). The state boundaries are compared to alkali-activated materials from the literature including denser binders. This work focuses on two compositions of dilute gels, formulated to specifically quantify the effects of pH and aluminum concentration on gel microstructure and rheology. Gels formulated at constant pH of 12.5 show a change in morphology and silicon coordination, but consistent mass fractal dimension as aluminum concentration is increased. This microstructural behavior contrasts the characterization of gels previously formulated with a variable pH (range 3–11) which is dependent on aluminum concentration. These results inform the complicated interactions in the polycondensation reaction of alkali-activated binders and lead to a state diagram which unifies many structure-property observations reported for these materials.

An efficient and recyclable catalytic system composed of palladium nanoparticles embedded over mesoporous TiO2 material (Pd@MTiO2) has been synthesized and its catalytic activity has been explored in Suzuki-Miyaura cross-coupling reaction of aryl halides in water medium. This catalytic system is a very simple and highly active protocol for carrying out the Suzuki coupling of aryl bromide and aryl chloride with boronic acids, which proceed smoothly in excellent yields under mild reaction conditions. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR), and N2 sorption studies are used to characterize the Pd@MTiO2 material. Environmentally friendly reaction conditions, high product yield, tolerance of variety of functionalities in the reactants and reusability suggested future potential of Pd@MTiO2 for the synthesis of a wide range of biaryl compounds.

Due to an increasing amount of waste tires produced yearly, environmental concerns arise as waste tires in landfills pose both a fire hazard, and a habitat for rodents and mosquitos. As a result, the reuse of waste tires in the form of waste rubber in concrete has been attempted. Previous research work has shown that the inclusion of waste rubber in concrete results in a drastic decrease in compressive strength. The limitations regarding the use of rubberized concrete are related to the interfacial transition zone between rubber and paste. Due to mismatch in free surface energy between rubber and cement paste, an interfacial gap is often reported to be present. This investigation aims to determine the effect of expansive cement, specifically calcium sulfoaluminate cement (CSA), has on the performance on rubberized cement samples, and its effect on the interfacial transition zone. A comprehensive experimental plan was carried out including pullout and compressive tests, scanning electron microscopy (SEM) imaging of fractured surface, and non-destructive tests through resonant frequency and dynamic mechanical analysis (DMA); furthermore, a temperature sweep via DMA was done to determine damping factor as a function of temperature. Results from compressive strength indicate a marked increase in the performance of rubberized samples with expansive cement. Pullout results, dynamic modulus and damping ratio values, shrinkage measurements, and scanning electron microscopy (SEM) imaging validate the hypothesis that a decreased interfacial gap at the rubber-paste interface obtained from using expansive cement results in increased mechanical performance.

The present study aims at examining the physico-chemical factors influencing the expansion characteristics of OPC–CSA blend in the presence of mineral admixtures. Three different admixtures: Class ‘F’ fly ash (‘F’FA), Class ‘C’ fly ash (‘C’FA) and silica fume (SF) were used as 15%, 15% and 5% replacement of total cementitious binder. Longitudinal expansion of cement pastes prepared at w/cm – 0.44 showed that the Class ‘F’FA increased the expansion whereas the Class ‘C’FA and SF reduced the expansion. The pore solution of the OPC–CSA cement pastes was extracted at different ages to monitor the concentration of various ionic species. The saturation level of ettringite was determined using a geochemical modeling program (GEMS). Furthermore, an upper bound of crystallization stress was estimated. The expansion behavior in the presence of Class ‘F’FA and SF was found to be influenced by the changes in the stiffness, whereas the expansion of the Class ‘C’FA-based mixture was governed by faster hydration of ye'elimite.

Alkali activation of a fly ash and slag mixture supposedly forms a combination of aluminosilicate and calcium silicate hydrate gel as reaction products. Fourier transform infrared spectroscopy (FTIR) is often used to characterize the complex nature of the reaction products. However, interpretation of FTIR results is difficult as the Si–O–T (T = Al, Si) vibrations from the initial ash, geopolymer product, unreacted slag, and calcium silicate hydrate yield an overlapping spectrum. This paper reports how the issue can be resolved by selectively dissolving calcium silicate hydrate and geopolymer product, and subtracting FTIR spectra of the insoluble residue from the original material to determine IR spectrum of the material dissolved.

Fiber reinforcements provide many benefits to cementitious composites, including reduction of crack widths and increases in ductility. However, the interfacial transition zone between fibers and hydrated cement can contain a high proportion of calcium hydroxide and porosity. With their high moduli of elasticity, carbon nanotubes and carbon fibers could provide substantial mechanical reinforcement at multiple length scales, but only if their bond to the matrix can be controlled. Surface treatments of fibers and addition of supplemental materials in the matrix can influence both the mechanical interaction at the interface and the dispersion of these relatively small reinforcements. We performed a broad study of Portland cement mortar mixtures containing silica fume, plain or silica-functionalized carbon nanotubes, and carbon fibers to characterize changes in fracture properties. The early age hydration kinetics of cement pastes containing carbon nanotubes were compared using isothermal calorimetry. Early age fracture surfaces of cement pastes containing carbon fibers were observed using a scanning electron microscope. The notched beam test method of the Two Parameter Fracture Model was used to determine the fracture properties of each mix. We observed that silica fume and silica functional groups improved the fracture performance of mixtures containing carbon nanotubes and carbon fibers. Further optimization of dosage, size, and interface strength is required to fully utilize carbon nanotubes in cementitious composites.

The degradation of hydration products of cement is known to cause changes in the micro- and nano-structure, which ultimately drive thermo-mechanical degradation of cement-based composite materials at elevated temperatures. However, a detailed characterization of these changes is still incomplete. This paper presents results of an extensive experimental study carried out to investigate micro- and nano-structural changes that occur due to exposure of cement paste to high temperatures. Following heat treatment of cement paste up to 1000 °C, damage states were studied by compressive strength test, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) atomic force microscopy (AFM) and AFM image analysis. Using experimental results and research from existing literature, new degradation processes that drive the loss of mechanical properties of cement paste are proposed. The development of micro-cracks at the interface between unhydrated cement particles and paste matrix, a change in C–S–H nano-structure and shrinkage of C–S–H, are considered as important factors that cause the thermal degradation of cement paste.

A new furfural functionalized polymer-amine grafted with copper catalyst has been designed and employed for the N -arylation, O-arylation and S-arylation reactions under an open air condition to afford the corresponding coupled products in good to excellent yields. This solid supported catalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), UV–vis spectroscopy and scanning electron microscope (SEM). The developed catalyst can be facilely recovered and reused five times without significant decrease in activity and selectivity. This result confirms that the polymer anchored complex was not leached during the reaction, suggesting the true heterogeneous nature of the catalyst.

Silver nanoparticles (Ag-NPs) have been finely dispersed at the mesoporous organic polymer via post-synthetic chemical grafting over mesoporous poly-triallylamine (MPTA-1). The resulting Ag-MPTA-1 nanomaterial has been characterized by elemental analysis, powder x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV–vis diffuse reflectance spectroscopy (DRS), thermogravimetric analysis (TGA), EPR spectroscopy and AAS elemental analysis. The Ag-MPTA-1 acts as an efficient heterogeneous nanocatalyst in the reduction of substituted nitrobenzenes via transfer hydrogenation. The material also showed excellent catalytic activity in one-step catalytic oxidative esterification of primary alcohols using molecular oxygen as a green oxidant. The catalyst is air-stable, inexpensive, easy to prepare and reused several times without significant decrease in activity and selectivity.

Palladium nanoparticles (Pd NPs) have been grafted at the surfaces of a Co-containing metal–organic framework material MCoS-1. The Pd NPs grafted material Pd(0)/MCoS-1 has been characterized by HR TEM, XPS and EPR spectroscopic analyses. Pd(0)/MCoS-1 showed excellent catalytic activities in Suzuki–Miyaura cross-coupling reaction for the synthesis of a diverse range of biaryl organics in water. Sonogashira cross-coupling between terminal alkynes and aryl halides has also been carried out over this Pd-nanocatalyst in water without the addition of any Cu co-catalyst. In both reactions the catalyst is easily recoverable and can be reused for several times without appreciable loss of catalytic activity. No evidence of the leaching of Pd from the catalyst during the course of reaction has been observed, suggesting true heterogeneity in our catalytic systems.

A new Schiff base oriented Co(III) complex, (CoL)Cl 4H2O (L = Schiff base), has been synthesized by careful design of the Schiff base ligand thorough oxidation of Co(II) to Co(III) during the reaction process. The complex has been characterized by single-crystal X-ray structure analysis and various spectral analyses. Structure analysis reveals that this monomeric complex crystallizes in triclinic P−1 space group. Supramolecular hydrogen bonding interactions among the guest water molecules and counter anion chloride leads to the formation of 1D water-chloride chain. A polymer anchored heterogeneous cobalt complex has been synthesized, characterized by various physicochemical techniques and successfully used for the oxidation of alkenes and sulfides using H2O2 as oxygen source. The influence of the various reaction parameters has been studied. The heterogeneous cobalt complex can be reused seven times without any significant loss in its catalytic activity.

This paper presents the microstructural development and hardening rate of fly ash-slag geopolymers. The solid precursors are treated with a potassium hydroxide-silicate activator of modulus 1.25. Ultrasonic wave reflection and Proctor penetration methods are used to determine the rate of hardening. Microstructural development is investigated using SEM-EDS, and the reaction rate is monitored using semi-adiabatic calorimetry. Both UWR and Proctor penetration methods capture changes in the hardening rate due to changes in the reaction mechanism. An increase in the rate of hardening is observed with the addition of slag. It is concluded that the calcium that dissolves from slag significantly influences both early and late age properties, and the availability of free calcium ions seems to prolong fly ash dissolution and enhance geopolymer gel formation. It is proposed that the hardening process is initiated by the precipitation of C-A-S-H and that rapid hardening continues due to accelerated geopolymerization.

An inexpensive, air-moisture stable and reusable PS–Pd(II)-furfural complex was synthesized by reacting polymeric amine with furfural to get polymer anchored ligand which was then reacted with Pd(OAc) 2 to get polymer anchored complex. This complex was characterized by different spectroscopic and elemental analyses. The activities of the Pd-complex were tested for the C C and C N cross-coupling reactions under various reaction conditions. The catalyst exhibits high catalytic activities for the coupling of various aryl halides with organoboronic acid, alkene, alkyne and amine providing excellent yields of desired product. Further, the catalyst can be easily recovered by simple filtration and reused up to five times without significant loss of its catalytic activity.

A new reusable polymer anchored Cu(II) complex was synthesized which can acts as an efficient heterogeneous catalyst for oxidation of olefins and alcohols with tert -butylhydroperoxide (TBHP) in aqueous medium. The present catalyst well oxidized styrene and other olefins to their allylic products and alcohols were converted to their corresponding aldehydes in good-to-moderate yields. This catalyst can be easily recovered by filtration and recycled without significant loss of its catalytic performances.

Polymer anchored oxovanadium catalyst was synthesized and characterized. The solid catalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), UV–vis diffuse reflectance spectroscopy (DRS), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). Its catalytic activity was evaluated for the oxidation of various alkenes, sulfides and aromatic alcohols with 30% H2O2 under mild reaction conditions. This catalyst was also effective for the oxidative bromination reaction of organic substrates with 80–100% selectivity of mono substituted products with H2O2/KBr at room temperature. The above reactions require minimum amount of H2O2, short time period and most importantly all the above reactions occur in aqueous medium. The developed catalyst can be facilely recovered and reused six times without significant decrease in activity and selectivity. This result confirms that the polymer anchored complex was not leached during the reaction, suggesting the true heterogeneous nature of the catalyst.

A simple and industrially viable protocol for C–N and C–O coupling was reported here. The polymer supported heterogeneous copper catalyst was prepared from chloromethyl polystyrene using a simple procedure. O-Arylation of substituted phenols with various aryl halides was achieved using this copper catalyst in DMSO medium. This heterogeneous copper catalyst, also efficiently works for the N-arylation of N–H heterocycles with aryboronic acids in methanol. This catalyst was also effective in amination reaction of primary amines with aryl halides as well as arylboronic acids in DMSO medium. The effects of solvent, base and temperature for the O-Arylation and amination reactions were reported. Further, the catalyst can be easily recovered quantitatively by simple filtration and reused up to several times without sufficient loss of its catalytic activity.

The Ullmann coupling of amines with aryl iodide as well as arylboronic acids and N(H)-heterocycles with arylboronic acids has been carried out efficiently using PS-LCu(I) catalyst. The copper complex has been prepared and characterized by using scanning electron microscope (SEM), elemental analysis, atomic absorption spectroscopy (AAS), Thermo gravimetric analysis and spectrometric methods like Fourier transform infrared spectroscopy (FTIR). The effects of various parameters such as temperature, solvent and base on the reaction system were studied. The reusability experiments show that the catalyst can be used five times without much loss in the catalytic activity.

A new polymer supported Cu(II) Schiff base complex was synthesized. The solid complex was characterized by Fourier transform infrared spectroscopy (FT-IR), UV–vis diffuse reflectance spectroscopy (DRS), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). Its homogeneous analogue was also prepared. The catalytic performances of the copper complex in oxidation reactions were evaluated for both homogeneous and heterogeneous systems. The copper(II) complex was found to be efficient catalyst for the oxidation of alkenes, alkanes and aromatic alcohols in the presence of hydrogen peroxide as oxidant at room temperature. The catalytic investigation revealed that the solid complex performs better than the homogeneous one as an oxidation catalyst. The solids containing the immobilized complex can be recovered from the reaction medium and reused almost five times, maintaining good catalytic activity. Furthermore, the in vitro toxicity of the ligand and complex was tested against the growth of bacterial species, viz., Staphylococcus aureus and Escherichia coli .

An inexpensive, air–moisture stable and reusable PS–Pd(II)–anthra complex was synthesized by reacting chloro-methylated polystyrene with anthranilic acid to get polymer anchored ligand which was then reacted with PdCl 2 to get polymer anchored complex. This complex was characterized by different spectroscopic and elemental analyses. The activity of the Pd-complex as catalyst was tested for the Suzuki, Heck, Sonogashira cross-coupling and also for amination and cyanation reactions under various conditions. The catalyst exhibits high catalytic activities for the coupling of various aryl halides with organoboronic acid, alkene, alkyne and amine along with the cyanation of aryl halides providing excellent yields of desired product. Further, the catalyst can be easily recovered quantitatively by simple filtration and reused up to five times without sufficient loss of its catalytic activity.

A new polystyrene anchored Pd(II) azo complex has been synthesized and characterized. The present Pd(II) azo complex behaves as a very efficient heterogeneous catalyst in the Suzuki coupling and Sonogashira coupling reaction in water medium. Aryl halides, coupled with phenylboronic acids (Suzuki–Miyaura reaction) or terminal alkyne (Sonogashira reaction), smoothly afford the corresponding cross-coupling products in excellent yields (83–100% yield for Suzuki reaction and 68–96% yield for Sonogashira reaction of aryl halides) under phosphine-free reaction conditions in the presence of polystyrene anchored Pd(II) azo complex catalyst in water medium. Furthermore, the catalyst has shown good thermal stability and recyclability. This polymer-supported Pd(II) catalyst could be easily recovered by simple filtration of the reaction mixture and reused for more than six consecutive trials without a significant loss of its catalytic activity.