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Controlling the BET Surface Area of Porous Carbon by Using the Cd/C Ratio of a Cd–MOF Precursor and Enhancing the Capacitance by Activation with KOH
Author(s) -
Li ZuoXi,
Zhang Xue,
Liu YiChen,
Zou KangYu,
Yue ManLi
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201603072
Subject(s) - biphenyl , calcination , benzene , metal organic framework , imidazole , ligand (biochemistry) , chemistry , specific surface area , porosity , crystallography , thermal decomposition , bet theory , cadmium , materials science , stereochemistry , adsorption , catalysis , organic chemistry , biochemistry , receptor
Herein, four new cadmium metal–organic frameworks (Cd–MOFs), [Cd(bib)(bdc)] ∞ ( 1 ), [Cd(bbib)(bdc)(H 2 O)] ∞ ( 2 ), [Cd(bibp)(bdc)] ∞ ( 3 ), and [Cd 2 (bbibp) 2 (bdc) 2 (H 2 O)] ∞ ( 4 ), have been constructed from the reaction of Cd(NO 3 ) 2 ⋅ 4 H 2 O with 1,4‐benzenedicarboxylate (H 2 bdc) and structure‐related bis(imidazole) ligands (1,4‐bis(imidazol‐1‐yl)benzene (bib), 1,4‐bis(benzoimidazol‐1‐yl)benzene (bbib), 4,4′‐bis(imidazol‐1‐yl)biphenyl (bibp), and 4,4′‐bis(benzoimidazol‐1‐yl)biphenyl (bbibp)) under solvothermal conditions. Cd–MOF 1 shows a 2D (4,4) lattice with parallel interpenetration, whereas 2 displays an interesting 3D interpenetrating dia network, 3 exhibits an unusual 3D interpenetrating dmp network, and 4 presents a 3D self‐catenated pillar‐layered framework with a Schäfli symbol of [4 3 ⋅ 6 3 ] 2 ⋅ [4 6 ⋅ 6 16 ⋅ 8 6 ]. The structural diversity indicates that the backbone of the bis(imidazole) ligand (including the terminal group and spacer) plays a crucial role in the assembly of mixed‐ligand frameworks. By using the pore‐forming effect of cadmium vapor, for the first time we have utilized these Cd–MOFs as precursors to further prepare porous carbon materials (PCs) in a calcination–thermolysis procedure. These PCs show different porous features that correspond to the topological structures of Cd–MOFs. Significantly, it was found that the specific surface area and capacitance of PCs are tuned by the Cd/C ratio of the MOF. Furthermore, the as‐synthesized PCs were processed with KOH to obtain activated porous carbon materials (APCs) with higher specific surface area and porosity, which greatly promoted the energy‐storage capacity. After full characterization, we found that APC‐bib displays the largest specific surface area (1290 m 2 g −1 ) and total pore volume (1.37 cm 3 g −1 ) of this series of carbon materials. Consequently, APC‐bib demonstrates the highest specific capacitance of 164 F g −1 at a current density of 0.5 A g −1 , and also excellent retention of capacitance (≈89.4 % after 5000 cycles at 1 A g −1 ). Therefore, APC‐bib has great potential as the electrode material in a supercapacitor.