Long-range ordered porous carbons produced from C-60

Abstract

Carbon structures with covalent bonds connecting C-60 molecules have been reported(1-3), but their production methods typically result in very small amounts of sample, which restrict the detailed characterization and exploration necessary for potential applications. We report the gram-scale preparation of a new type of carbon, long-range ordered porous carbon (LOPC), from C-60 powder catalysed by alpha-Li3N at ambient pressure. LOPC consists of connected broken C-60 cages that maintain long-range periodicity, and has been characterized by X-ray diffraction, Raman spectroscopy, magic-angle spinning solid-state nuclear magnetic resonance spectroscopy, aberration-corrected transmission electron microscopy and neutron scattering. Numerical simulations based on a neural network show that LOPC is a metastable structure produced during the transformation from fullerene-type to graphene-type carbons. At a lower temperature, shorter annealing time or by using less alpha-Li3N, a well-known polymerized C-60 crystal forms owing to the electron transfer from alpha-Li3N to C-60. The carbon K-edge near-edge X-ray absorption fine structure shows a higher degree of delocalization of electrons in LOPC than in C-60(s). The electrical conductivity is 1.17 x 10(-2) S cm(-1) at room temperature, and conduction at T < 30 K appears to result from a combination of metallic-like transport over short distances punctuated by carrier hopping. The preparation of LOPC enables the discovery of other crystalline carbons starting from C-60(s).