Green and selective hydrogenation of aromatic diamines over the nanosheet Ru/g-C_(3)N_(4)-H_(2) catalyst prepared by ultrasonic assisted impregnation-deposition method

In this study,nanosheet g-C_(3)N_(4)-H_(2) was prepared by thermal exfoliation of bulk g-C_(3)N_(4) under hydrogen.A series of Ru/g-C_(3)N_(4)-H_(2) catalysts with Ru species supported on the nanosheet g-C_(3)N_(4)-H_(2) were synthesized via ultrasonic assisted impregnation-deposition method.Ultrafine Ru nanoparticles(<2 nm)were highly dispersed on nanosheet g-C_(3)N_(4)-H_(2).Strong interaction due to Ru-Nx coordination facilitated the uniform distribution of Ru species.Meanwhile,the involvement of surface basicity derived from abundant nitrogen sites was favourable for enhancing the selective hydrogenation performance of bi-benzene ring,i.e.,almost complete 4,40-diaminodiphenylmethane(MDA)conversion and>99%4,40-diaminodicyclohexylmethane selectivity,corresponding to a reaction activity of 35.7 mol_(MDA) mol_(Ru)^(-1) h^(-1).Moreover,the reaction activity of catalyst in the fifth run was 36.5 mol_(MDA) mol_(Ru)^(-1) h^(-1),which was comparable with that of the fresh one.The computational results showed that g-C_(3)N_(4) as support was favorable for adsorption and dissociation of H_(2) molecules.Moreover,the substrate scope can be successfully expanded to a variety of other aromatic diamines.Therefore,this work provides an efficient and green catalyst system for selective hydrogenation of aromatic diamines.

Thermo-oxidative Oligomerization of Aromatic Diamine

Molecular spectroscopy(electronic,FT-IR,NMR),methods of thermal and elemental analysis were used for the first time to describe the process of thermo-oxidative oligomerization of 1,3-bis-(4-aminophenoxy)benzene.Introduction of this monomer into linear and network copolymers makes it possible to improve processability,mechanical strength and heat resistance of materials.The structures of copolymers obtained by thermo-oxidation of the diamine in various thermal regimes were studied.It was demonstrated that during prolonged heating of this diamine in air in the temperature range from 220 to 320°C,oligomeric aromatic diamines were formed;these products contained fragments of benzenoid and quinoid types.

The production of biobased diamines from renewable carbon sources: Current advances and perspectives

Bio-based diamines are considered to be a promising alternative to traditional fossil-fuel-based diamines,the important platform chemical for the synthesis of polymer materials.In this review,the current status of the art of the synthesis of aliphatic and aromatic diamines from renewable biomass are considered.In the case of aliphatic diamines,we describe strategies for biologically producing diamines with different carbon numbers including 1,3-diaminopropane,1,4-butanediamine,1,5-pentanediamine,1,6-diaminohexane,1,8-diaminooctane,1,10-diaminodecane,and 1,12-diaminododecane.In addition,aromatic diamines produced from various kinds of renewable biomass,including lignin,cashew nut shell,and terpenoids,are reviewed here.Furthermore,the application of typical diamines in synthesis of polyurethane and polyamide are also reviewed.

Synthesis and Characterization of Novel Polyimides Based on Pyridine-containing Diamine

A new aromatic diamine monomer containing pyridine unit, 2,6-bis （4-aminophenoxy- 4＇-benzoyl）pyridine（BABP）, was synthesized in three steps, starting from 2,6-pyridinedicarboxyl chloride. A series of novel pyridine-containing polyimides were prepared v/a the polycondensation of BABP with various aromatic dianhydrides through poly（amic acid） precursors, and thermal or chemical imidization of the precursors. The polyimides exhibit desirable properties, e.g., good solubility in N-methyl-2-pyrrolidone and m-cresol, excellent thermal stability and film-forming capability, as well as high inherent viscosity, indicating high molecular weight.

SYNTHESIS AND PROPERTIES OF NOVEL POLY(IMINO KETONE)S AS HIGH-PERFORMANCE POLYMERS

Di(4-bromophenyl)ketone and various aromatic diamines as the monomers,a series of novel poly(imino ketone)s (PIKs)have been synthesized via palladium-catalyzed aryl amination,which is Hartwig-Buchwald polycondensation reaction.The structures of PIKs are characterized by means of elemental analysis,FT-IR,~1H-NMR and UV-Vis spectroscopy. The results show a good agreement with the proposed structure.The general properties of PIKs are studied by DSC,TG and wide-angle X-ray diffraction,the solubility behavior is...

Synthesis and Characterization of Polyamides Based on Dimer Acid

A series of dimer acid-based polyamides were synthesized by melt-polycondensation of dimer acid and various aromatic diamines, and were characterized by Fourier transform infrared spectrum （FT-IR） and nuclear magnetic resonance （^1H NMR）. The physical properties of the polyamides, such as glass transition temperature, melting temperature, decomposition temperature and mechanical properties were also investigated. The polyamides＇ intrinsic viscosity ranges from 1.8 dL·g^-1 to 2.2 dL·g^-1, and the melting temperature ranges from 140 ℃ to 181 ℃. The glass transition temperatures, observed from dynamic mechanical analysis, fall in the range of 34.8-48.2 ℃. The physical and mechanical properties of the resultant polyamides are similar to those of the PA1212. The heat resistance and mechanical properties of poly （4, 4′-diphenylsulfone dimeramide） （PSD） and poly（4, 4′-di pb enyl dimeramide） （PPDI） are comparable to those of PA 1212.

Fluorescent MOF-based nanozymes for discrimination of phenylenediamine isomers and ratiometric sensing of o-phenylenediamine

Although peroxidase-like nanozymes have made great progress in bioanalysis,few current nanozymebased biosensors are constructed for discriminating isomers of organic compounds.Herein,fluorescent metal-organic framework(MOF)-based nanozyme is utilized for phenylenediamine isomers discrimination and detection.NH_(2)-MIL-101(Fe),as a member of Fe-based MOFs,functions as not only fluorescent indicator but also peroxidase mimics.In the presence of H_(2)O_(2),NH2-MIL-101(Fe) can catalyze the oxidation of o-phenylenediamine(OPD) and p-phenylenediamine(PPD) into their corresponding oxidation products(OPDox and PPDox),which in turn quench its intrinsic fluorescence at 445 nm via inner filter effect(IFE).Differently,a new fluorescence peak at 574 nm is observed for OPDox.Thus,a ratiometric fluorescence method for the detection of OPD can be designed with the fluorescence intensity ratio F_(574)/F_(445)as readout.This proposed strategy displays excellent discrimination ability for three phenylenediamines and may open new applications of MOFs in environmental science.