Metal organic frameworks (MOFs) are porous crystalline materials composed of metal ions or clusters of metal ions coordinated with organic linkers (such as terephthalic acid, 1,3,5-benzenetricarboxylic acid, or imidazoles) MOFs exhibit tunable structures, low density, ultrahigh surface area and have various potential applications in catalysis, hydrogen storage, and adsorption/separation of liquid or gaseous mixtures Among the MOFs structures, the zeolitic imidazolate frameworks (ZIFs) have recently attracted considerable attention In these materials, metal atoms such as Zn2+ are linked through N atoms by the ditopic 2-methylimidazolate ligand to form neutral frameworks ZIF-8 has a sodalite zeolite-type topology with cages of 116 A and pores of 34 A in diameter ZIF-8 are characterized by high thermal stability (550 oC in N2), large surface area (BET: 1630 m2/g) and high resistance to various solvents Concerning ZIF-8 chemical properties, these materials can successfully be used for hydrogen, carbon dioxide and iodide storage, Knoevenagel condensations, cycloadditions, oxidations, trans-esterification, and Friedel-Crafts alkylations Variations of synthetic parameters (solvent, concentration, temperature, time, molar ratio of reactants) are commonly used to manipulate the morphology and size of ZIF-8 crystals In this work, we demonstrate that the reactivity of the Zn(+2) salt in the growth solution can also markedly affect the size and the morphology of ZIF-8 particles Small ZIF-8 nanocrystals with diameters varying between ca 50 and 200 nm were obtained with reactive zinc salts like Zn(acac)2, Zn(NO3)2, ZnSO4 or Zn(ClO4)2 The use of ZnCl2, Zn(OAc)2 or ZnI2 afforded crystals with sizes varying between ca 350 and 650 nm Finally, the low reactive ZnBr2 was found to generate microsized crystals These significant changes in particle size induced distinctive changes in adsorption properties as demonstrated by BET measurements but also in the catalytic performances of ZIF-8 crystals in a Knoevenagel condensation used as model The small sized crystals produced from Zn(NO3)2 exhibit the highest surface area and the best catalytic activity

Controlling ZIF-8 nano and microcrystal formation and reactivity through zinc salts variations

Co-MOF@MXene-carbon nanofiber-based freestanding electrodes for a flexible and wearable quasi-solid-state supercapacitor

Supercapacitors are projected as one of the most promising candidates for next-generation energy storage devices. Herein, we strategically developed a microporous two-dimensional Ni-metal organic framework (MOF: IITKGP-20A , IITKGP stands for the Indian Institute of Technology Kharagpur) which is highly scalable and thermodynamically stable over a wide pH range (2–10), intended for energy storage applications . Graphene oxide (GO) with different wt% (3, 5, and 7) was introduced with the MOF precursors to form in-situ MOF@GO composites ( IITKGP-20A-GO3 , IITKGP-20A-GO5 , and IITKGP-20A-GO7 respectively), out of which IITKGP-20A-GO3 exhibits significantly high specific capacitance value (∼840 F g −1 at 2 A g −1 ), which is one of the highest among the bare MOFs and their composites/derived materials. To verify its practical potentiality as positive electrode material, an asymmetric supercapacitor (ASC) device was fabricated displaying the specific capacitance of 111.4 F g −1 at a current density of 2 A g −1 while maintaining a high specific capacity of 65 F g −1 even at a higher current density of 10 A g −1 . Moreover, the device produced 30.7 W h kg −1 (0.031 W h cm −3 ) energy density with a very high power density of 388.5 W kg −1 (0.394 W cm −3 ) with excellent retention of 84% cycle life up to 7000 cycles. A new highly scalable and pH stable 2D Ni-MOF ( IITKGP-20A ) and in situ MOF@GO composites ( IITKGP-20A-GO ) are synthesized in which IITKGP-20A-GO3 exhibits significantly high specific capacitance value of 840 F g −1 at 2 A g −1 , one of the highest among the bare MOFs and their composites/derived materials. An ASC device produced 30.7 W h kg −1 energy density with a very high power density of 388.5 W kg −1 exhibiting an excellent retention of 84% cycle life up to 7000 cycles. • Strategic designs and development of highly scalable and pH stable 2D Ni-MOF-based composites. • Electrochemical performance is highly dependent on the GO% of the MOF composites. • IITKGP-20A-GO3 exhibits highest specific capacitance of ∼ 840 F g −1 at 2 A g −1 current density. • ASC device exhibited maximum energy density of ∼ 30.7 W h kg −1 at a power density of 388.5 W kg −1 

Highly scalable and pH stable 2D Ni-MOF-based composites for high performance supercapacitor

Recent Progress of the Active Materials with Various Micro-structures for Flexible Textile-Based Supercapacitors

Nitrogen‐doped porous carbon (NPC@ZIF‐11) and boron‐NPC (BNPC@ZIF‐11) materials were synthesized by pyrolysis methods, and structural characterization of the compounds was carried out by scanning electron microscopy, transmission electron microscopy, Fourier‐transform infrared spectroscopy, X‐ray diffraction, Brunauer–Elmet–Teller technique, Raman spectroscopy, and inductively coupled plasma‐mass spectrometry techniques. The ZIF‐11 was converted to the NPC@ZIF11 by pyrolysis. BNPC@ZIF‐11 was fabricated from NPC@ZIF‐11 by pyrolysis in the presence of phenylboronic acid. The fabric supercapacitor, sandwich‐type supercapacitor, and Li‐ion battery performances of NPC@ZIF‐11 and BNPC@ZIF‐11 were investigated. The capacity of the Li‐ion cell was found as 720 mAh g−1 for the first cycle, and it was decreased to 250 mAh g−1 after 100 cycles. The capacitance values of the cylindrical devices were 92 F g−1 and 115.6 F g−1, for C1 and C4000 in KOH electrolytes. The BNPC@ZIF‐11 was used as an electrode material on cotton fabric, and the highest obtained capacitance was 72.8 mF for 0.1 mA, which is a promising result for wearable energy storage materials.

Boron‐doped porous carbon material derived from ZIF‐11: Investigation of cotton fabric supercapacitor and Li‐ion battery performances

In view of the respective advantages of electrical double layer capacitance (EDLC) and pseudocapacitance, the development of electrode materials with dual energy storage mechanisms (EDLC and pseudocapacitance) will play a significant role in maximizing the overall capacitance performance. In this paper, the core-shell fibers with dense zeolite imidazole framework (ZIF) coating were synthesized on the electrospun composite nanofiber substrate by a rapid in-situ growth strategy. After pyrolysis of ZIFs(shell)@PAN/PVP(core) fibers, heteroatom-doped porous carbon fiber materials with high specific surface area (410.55 m2 g-1) were obtained. It not only had a layered porous structure, but also fully exposed the doped active sites, which made it have the advantages of EDLC and pseudocapacitance. As expected, the prepared porous carbon materials doped with rich heteroatom, as supercapacitor electrode materials, exhibited large specific capacitances of 492.7 F g−1 at a current density of 1 A g−1 and 406.4 F g−1 at 10 A g−1. After 5000 cycles of galvanostatic charge-discharge at 10 A g−1, its capacitance retention rate was as high as 98.65%, showing excellent charge storage performance and good cycle stability. Therefore, this work presents an effective strategy for the design and preparation of supercapacitor electrode materials with dual energy storage mechanisms.

Lan Xu

Papers

Heteroatom-doped porous carbon derived from zeolite imidazole framework/polymer core-shell fibers as an electrode material for supercapacitor