Xuehong Ren

A Hexagonal Covalent Porphyrin Framework as an Efficient Support for Gold Nanoparticles toward Catalytic Reduction of 4-Nitrophenol

A hexagonal porphyrin-based porous organic polymer, namely, CPF-1, was constructed by 3+2 ketoenamine condensation of the C2 -symmetric porphyrin diamine 5,15-bis(4-aminophenyl)-10,20-diphenylporphyrin and 1,3,5-triformylphloroglucinol. This material exhibits permanent porosity and excellent thermal and chemical stability. CPF-1 can be employed as a superior supporting substrate to immobilize Au nanoparticles (NPs) as a result of the strong interactions between Au NPs and the CPF support. An Au@CPF-1 hybrid was synthesized by an interfacial solution infiltration method with NaBH4 as reducing agent. Au NPs (5 nm) grew on CPF-1 and were distributed without aggregation. Moreover, Au@CPF-1 exhibits superior catalytic activity compared to many other reported Au-based catalysts for the reduction of 4-nitrophenol in the presence of NaBH4 . In addition, Au@CPF-1 has excellent stability and recyclability, and it can be reused for three successive reaction cycles without loss of activity. The dense distribution of phenyl rings on the channel walls of the CPF support can reasonably be regarded as the active sites that adsorb the 4-nitrophenol molecule through hydrogen-bonding and C-H⋅⋅⋅π interactions, as was confirmed by the X-ray structure of model compound DAPP-Benz.

Optical recognition of alkyl nitrile by a homochiral iron(II) spin crossover host

A homochiral complex 1·MeCN was synthesized by the multicomponent self-assembly of (R)-phenylethylamine, 1-methyl-2-imidazolecarboxaldehyde and iron(II) ions in acetonitrile solution. X-ray crystallography analysis revealed that complex 1·MeCN crystallized in the chiral space group P21. The octahedral coordination mononuclear [FeL3]2+ cations are stacked into a left-handed double helix supramolecular structure along the a axis with uncoordinated acetonitrile molecules filling the helical channel. Interestingly, when 1·MeCN redissolved in racemic lactonitrile (LN) or methylglutaronitrile (MGN), the [FeL3]2+ cations can recognize one enantiomeric alkyl nitrile by forming 1·1/3(R)-LN or 1·1/3(S)-MGN crystals. 1·1/3(R)-LN and 1·1/3(S)-MGN crystallized in the P212121 space group, and the [FeL3]2+ cations are stacked in a triple helix mode with the enantiomeric alkyl nitrile captured in the helical channel. Magnetic measurement indicated that 1·MeCN displayed spin-crossover at 355 K, while the transition temperature became 220 K after desolvation. However, 1·1/3(R)-LN and 1·1/3(S)-MGN exhibited incomplete and reversible spin-crossover behaviors at about 363 K. The results demonstrated that the mononuclear iron(II) complex could be used as a host for racemic alkyl nitrile separation, and the spin-crossover property was influenced by the process of chiral recognition.

A three-dimensional porphyrin-based porous organic polymer with excellent biomimetic catalytic performance

A highly stable porphyrin-based porous organic polymer PPOP-1(Fe) with a three-dimensional diamond structure was synthesized via imine condensation of a tetrahedral aldehyde and a linear porphyrin diamine. PPOP-1(Fe) exhibits excellent catalytic activity as a biomimetic catalyst, because the heme-like porphyrin active centers in PPOP-1(Fe) are exposed toward the open channels, thus accelerating the catalytic oxidation reactions.

Integrating spin-crossover nanoparticles with silver nanowires: toward magnetic and conductive bifunctional nanomaterials

AgNWs@SCO nanocomposites were constructed by in situ growing spin-crossover (SCO) nanoparticles on silver nanowires (AgNWs). The obtained AgNWs@[Fe(Htrz)2(trz)](BF4) (AgNWs@SCO-1) and AgNWs@Fe(pz)[Pt(CN)4] (AgNWs@SCO-2) nanomaterials were characterized by FT-IR, PXRD, Raman spectroscopy, SEM and TEM. SEM images show that SCO NPs grow on the surface of the AgNWs, and their size and shape can be tuned by controlling the amount of added iron(II) salt. The magnetic measurements exhibit hysteresis loops with 45 K (Tc↑ = 385 K, Tc↓ = 340 K) for SCO-1 and 31 K (Tc↑ = 290 K, Tc↓ = 259 K) for SCO-2. It is interesting that both AgNWs@SCO nanocomposites retain spin-crossover behaviour with hysteresis loops with 50 K (Tc↑ = 395 K and Tc↓ = 345 K) for AgNWs@SCO-1 and 34 K (Tc↑ = 289 K and Tc↓ = 255 K) for AgNWs@SCO-2. The hot pressing method is used to transfer AgNWs@SCO nanocomposites to flexible PET substrates for a four-probe conductivity test. The conductivities of AgNWs@SCO-1 and AgNWs@SCO-2 are consistent with that of the individual AgNWs over the 100–350 K range, indicating that AgNWs@SCO nanocomposites exhibit good conductivity. The combination of both spin-crossover properties and conductive properties in AgNWs@SCO materials provides a great prospect for their application in devices.

CCDC 1426230: Experimental Crystal Structure Determination

Related Article: Feng-Li Zhang, Lei Tian, Long-Fang Qin, Jia-Qian Chen, Zaijun Li, Xuehong Ren, Zhi-Guo Gu|2016|Polyhedron|104|9|doi:10.1016/j.poly.2015.10.055