Organic–inorganic metal halides (OIMHs) with unique structural flexibility possess excellent photoelectric properties. They are regarded as next-generation photovoltaic materials, phosphors, semiconductors, and ferroelectrics. The metal-halide units in OIMHs are good microscopic building blocks of nonlinear optical crystals for laser wavelength conversion. However, most OIMHs are absent from nonlinear optics owing to their macroscopic nonlinear optical (NLO)-inactive centrosymmetric crystal structure. In this study, two new lead-free OIMHs, (TMEDA)SbI 5 and (TMEDA)BiI 5 (where TMEDA 2+ is N , N , N ′-trimethylethylenediammonium), having 1D structure, crystallized in the orthorhombic system with a non-centrosymmetric P 2 1 2 1 2 1 space group, are synthesized. Remarkably, upon 2090 nm laser irradiation, both compounds possess a strong infrared (IR) nonlinear optical response of the same magnitude as AgGaS 2 , which is a benchmark semiconductor-type nonlinear optical crystal. In addition, under the excitation of ultraviolet and visible lights, both compounds produce self-trapped exciton-induced red-light emission. First-principles electronic structure calculations reveal that the optical properties originate from the electronic transitions within the inorganic metal-halide group. The obtained results indicate that both compounds are potential photoelectric materials for laser frequency conversion and fluorescence, and the observation of NLO effect in these two compounds verifies that OIMHs are also good candidates for NLO crystals.
In order to ameliorate the issues of corrosion and high regeneration energy associated with traditional biphasic solvents, a nonaqueous biphasic solvent has been proposed as a potential alternative. This study introduces Tetramethylethylenediamine (TMEDA) as a phase splitter within the Ethanolamine (MEA)/Dimethyl sulfoxide (DMSO) system, resulting in a novel nonaqueous biphasic solvent, TMEDA/MEA/DMSO. Compared with other screened phase splitters, the appropriate polar size and intermolecular interaction force of TMEDA are the key factors that make it comply with the screening of nonaqueous biphasic solvent. When the mass ratio of TMEDA/MEA/DMSO is maintained at 3:3:4, the CO 2 loading attains 0.54 mol (CO 2 )/mol (MEA), with the rich phase comprising 75 % of the total. 13 C NMR and FT-IR characteristics showed that the absorbent product is mainly in the form of MEACOO − /MEAH + . Absorption and phase separation mechanisms of absorbent elucidated by DFT calculations and molecular dynamics simulations. The limited opportunity for TMEDA to interact with MEA molecules emerges as the primary reason for its reduced involvement in the reaction, with the inclusion of TMEDA intensifying the aggregation of MEACOO − /MEAH + and triggering phase transition. In comparison to a 30 wt% MEA water-based absorbent, TMEDA/MEA/DMSO exhibits a 40 % reduction in regeneration energy (estimate) and possesses energy-saving attributes, rendering it a promising candidate for CO 2 capture.
Wang Jiancheng,Ding Yunqiao,Wang Shijie,Yang Pengfei
The urethane reaction of 1,3-propanediol with phenyl isocyanate is monitored by means of in situ FTIR. 1,4-Diazabicyclo[2.2.2]octane (DABCO) and N , N , N ′, N ′-tetramethylethane-1,2-diamine (TMEDA) are used as catalysts. Reaction rates are calculated, and reaction kinetics are studied. Furthermore, Gaussian programs are used to calculate steric configuration and electronegativity of those two diamines. The electronegativity of TMEDA is greater than that of DABCO, but the steric hindrance of DABCO in nitrogen atom is smaller. Steric hindrance plays a more important part in reaction kinetics, which makes the reaction to be catalyzed by DABCO at a faster rate. Finally, activation energy, activation enthalpy, and activation entropy for the reaction are calculated, followed by the discussion of reaction mechanism.
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