Benzoate Acid-Dependent Lattice Dimension of Co-MOFs and MOF-Derived CoS2@CNTs with Tunable Pore Diameters for Supercapacitors

• Published in: Inorganic chemistry Vol. 56; no. 11; pp. 6184 - 6196
• Main Authors: Zou, Kang-Yu, Liu, Yi-Chen, Jiang, Yi-Fan, Yu, Cheng-Yan, Yue, Man-Li, Li, Zuo-Xi
• Format: Journal Article
• Language: English
• Published: American Chemical Society 05-06-2017
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.7b00200

Herein three novel cobalt metal–organic frameworks (Co-MOFs) with similar ingredients, [Co(bib)­(o- bdc)]∞ (1), [Co2(bib)2­(m- bdc)2]∞ (2), and {[Co­(bib)­(p- bdc)­(H2O)]­(H2O)0.5}∞ (3), have been synthesized from the reaction of cobalt nitrate with 1,4-bis­(imidazol-1-yl)­benzene (bib) and structure-related aromatic acids (1,2-benzenedicarboxylic acid = o -bdc, 1,3-benzenedicarboxylic acid = m -bdc, and 1,4-benzenedicarboxylic acid = p -bdc) by the solvothermal method. It is aimed to perform systematic research on the relationship among the conformation of benzoate acid, lattice dimension of Co-MOF, and pore diameter of MOF-derived carbon composite. Through the precursor strategy, Co-MOFs 1–3 have been utilized to synthesize porous cobalt@carbon nanotube composites (Co@CNTs). After the in situ gas-sulfurization, secondary composites CoS 2 @CNTs were successfully obtained, which kept similar morphologies of corresponding Co@CNTs without destroying previous highly dispersed structures. Co-MOFs and two series of composites (Co@CNTs and CoS 2 @CNTs) have been well characterized. Topology and Brunauer–Emmett–Teller analyses elucidate that the bdc 2– ion could control the pore diameters of MOF-derived carbon composites by adjusting the lattice dimension of Co-MOFs. The systematic studies on electrochemical properties demonstrate that (p)- CoS 2 @CNT possesses hierarchical morphology, moderate specific surface area, proper pore diameter distribution, and high graphitization, which lead to remarkable specific capacitances (839 F g–1 at 5 mV s–1 and 825 F g–1 at 0.5 A g–1) in 2 M potassium hydroxide solution. In addition, the (p)- CoS 2 @CNT electrode exhibits good electrochemical stability and still retains 82.9% of initial specific capacitance at the current density of 1 A g–1 after 5000 cycles.