Unraveling the relationship of the pore structures between the metal-organic frameworks and their derived carbon materials

Abstract

Metal-organic frameworks (MOFs) derived carbon-based materials have been extensively studied and applied for energy storage and conversion because of their high porosity, and uniform heteroatom-doping. However, up to now, no systematic study on the relationship of the pore structures of MOFs and their corresponding carbonaceous materials. Herein, two isostructural porphyrinic-based MOFs, microporous PCN-224 and mesoporous PCN-222 were carefully selected as the precursors to fabricate the N-doped carbons to investigate their relationship of their pore features due to they have same components but different pore structures. After pyrolysis, the obtained porous N-doped carbon materials were denoted as PCN-222-x and PCN-224-x (x is pyrolysis temperature, x = 1000, 800). Compared with the precursors, the four N-doped carbon samples showed very low BET surface areas. As for PCN-224-1000, the micropores of 1.9 nm in the microporous precursor were disappeared and a new micropore and several types of mesopores were formed. While as for PCN-222-1000, no micropore was observed and the hexagonal mesopores of 3.4 nm shrinked to 3.0 nm and several mesopores in the range of 3.0–17 nm were also formed. Moreover, after treated with NH3, PCN-224-1000-NH3 exhibited 60% CO faradaic efficiency at −0.9 V vs. RHE (the reversible hydrogen electrode) in the electrochemical CO2 reduction reaction. This work demonstrates that the pores of MOF precursors could affect the pore structures, and catalytic properties of their corresponding carbons.