2 research outputs found
Evolution of Phosphorus-Containing Groups on Activated Carbons during Heat Treatment
Two types of activated
carbons have been prepared by H<sub>3</sub>PO<sub>4</sub> activation
of lignocellulose and by H<sub>3</sub>PO<sub>4</sub> modification
of activated carbon, and then heat-treated at
temperatures from 400 to 900 °C in an atmosphere of N<sub>2</sub> or H<sub>2</sub> to investigate the evolution of phosphorus-containing
groups. Elemental analysis, X-ray photoelectron spectroscopy, <sup>31</sup>P nuclear magnetic resonance, nitrogen adsorption, and scanning
electron microscopy have been used to analyze the physicochemical properties of the activated carbons.
The results show that C–O–P linkages of phosphorus-containing
groups can progressively evolve into C–P–O, C<sub>3</sub>–PO, C<sub>3</sub>–P, and eventually elemental
phosphorus as a result of heat treatment. Phosphate-like groups are
much more thermally stable in an N<sub>2</sub> than in an H<sub>2</sub> atmosphere. In N<sub>2</sub>, C–O–P linkages significantly
evolve into C–P–O and C<sub>3</sub>–PO
at up to 800 °C, whereas C<sub>3</sub>–P linkages are
not formed even at 900 °C. In H<sub>2</sub>, the corresponding
evolution remarkably occurs at 500 °C, forming C<sub>3</sub>–P
linkages and eventually elemental phosphorus. Moreover, the two activated
carbons exhibit different evolution trends, suggesting that the evolution
happens more easily for phosphorus-containing groups located on the
edges of graphite-like crystallites than those in the lattice. Finally,
we propose different evolution pathways of phosphorus-containing groups
upon heat treatment in N<sub>2</sub> and H<sub>2</sub> atmospheres
KO<sup><i>t</i></sup>Bu-Promoted C4 Selective Coupling Reaction of Phenols and [60]Fullerene: One-Pot Synthesis of 4‑[60]Fullerephenols under Transition-Metal-Free Conditions
A KO<sup><i>t</i></sup>Bu-promoted direct coupling reaction
of phenols and [60]Âfullerene was disclosed. The reaction occurs exclusively
at the C4-position of phenols with high regioselectivity and provides
an efficient and inexpensive manner to various 4-[60]Âfullerephenols
in good yields. The electrochemical properties of
the products render the method attractive and valuable