Delicate control over structural phase transition provides
advanced
approaches for the fabrication of the desired well-ordered nanoarchitectures
on surfaces. The participation of intrinsic metal adatoms in pure
organic systems can facilitate the structural phase transition by
direct capture of surface metal adatoms and forming metal–organic
bonds. However, most of the situations occur at low coverage; such
structural phase transition at a higher molecular concentration is
limited to some extent due to the poor migration ability. Thus, high-concentration
phase transition needs to be explored, which might be significant
for the design and exploitation of large-scale ordered metal–organic-related
nanomaterials. Herein, we report the phase transition of pyrene-4,5,9,10-tetraone
(PT) molecules at high coverage (∼1 monolayer (ML)) on Au(111)
from hydrogen-bonded row-like nanostructures to metal–organic
honeycomb networks by coordinating with surface Au adatoms as demonstrated
by scanning tunneling microscopy (STM). Combined with density functional
theory (DFT) calculations, we demonstrate that identical molecular
density (or unit cells) of two nanostructures should be the key, which
makes it possible to realize phase transition possibly by in situ
rotation and coordinating with the gold adatoms. Also, the phase transition
causes the modulation of electronic properties from semiconductive
ones to metallic ones.
A novel O-Diphenol Triazine Microporous Polymer was successfully synthesized by the one-step Friedel-Crafts reaction of cyanuric chloride and 1,2-Dihydroxybenzene(catechol) in the presence of dichloromethane and anhydrous AlCl3 as solvents and catalyst, respectively. The polymer was characterized by FTIR, 13C CP/MAS NMR, XDR and TGA. The study found that the polymer is an amorphous structure containing trace amounts of quinines. The polymer has good thermal stability, and the 5% weight loss temperature is 260 °C under nitrogen conditions. The surface area of the polymer is 154.08 m2/g, the pore diameter is 5.55 nm and its distribution is mainly in the mesoporous region by adsorption-desorption of N2 at 77 K.
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