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A hybrid material of carbon nanotubes (CNTs) and Mn-based metal organic frameworks (Mn-MOF) was synthesized and used as a Mn-based supercapacitor electrode material. The incorporation of CNTs into Mn-MOF led to an inherent improvement in conductivity and an intrinsic increase in specific capacitance (from 43.2 F g À1 for pure Mn-MOF to 203.1 F g À1 for CNTs@Mn-MOF). Furthermore, the symmetrical supercapacitor based on the CNTs@Mn-MOF exhibited excellent power density and outstanding stability even after 3000 cycles with 88% retention of the initial capacitance. This research exploited a new direction for developing Mn-based supercapacitor materials and provided an effective method to improve capacitive performance of MOFs materials.

Currently, the development of two kinds of materials from a single precursor has been an important frontier in material synthesis. In this study, we have successfully fabricated a single precursor using metal-organic framework (MOF) (zeolitic imidazolate framework, ZIF-8) and carbon nanotubes (CNTs). ZnO quantum dots (QDs)/carbon/CNTs and porous N-doped carbon/CNTs have been selectively synthesized from the single ZIF-8/CNTs template. When the two derived materials were used for supercapacitor electrode, they showed high capacitance values (185 F g -1 g for ZnO QDs/carbon/CNTs at 0.5 A g -1 and 250 F g -1 g for porous N-doped carbon/CNTs at 1 A g -1 , respectively). Further, an all-solid-state asymmetric supercapacitor (ASC) device using ZnO QDs/carbon/CNTs as the positive electrode and porous N-doped carbon/CNTs as the negative electrode was fabricated, and this device could reach a working potential of 1.7 V, delivering a maximum energy density of 23.6 W h kg -1 and a maximum power density of 16.9 kW kg -1 , which is better than those of the ZnO-based symmetric or asymmetric supercapacitor devices. fact that they have high theoretical capacitance values, low cost, environmental friendliness, high electrochemical stability, etc. 2 However, the low charge storage capability and narrow working potential window limit their further applications in SCs. In an effort to address this challenge, various carbon materials, such as graphene, 3-9 reduced graphene oxides, 10-13 carbon nanotubes (CNTs), 2, 14-18 graphitic carbon nanofibers, 19, 20 carbon arrays 21 and activated carbon, 22 have been widely used to modify ZnO electrode materials due to their contribution on additional electric double layer capacitance and enlarged working potential window. However, the weak adhesive force between carbon materials and ZnO nanocrystals usually leads to pulverization of the electrodes, resulting in poor cycle stability. 23 Besides, the maximum reported potential window for ZnO/carbon materials electrodes is 1 V, which obviously results in limited energy density. Rational design and facile synthesis of ZnO-based supercapacitors for excellent cycling performance and outstanding energy density still remain a challenge. Among multifarious strategies, fabricating uniformly dispersed small ZnO particles in carbon matrix and developing asymmetric supercapacitors (ASCs) to maintain the mechanical integrity of the composite material and enlarge the working potential window can be effective approaches to solve the main problems. 24, 25 As well as we know, small enough particles embedded into carbon matrix can produce strong adhesion, and quantum dot (QD) can be a suitable candidate among various small scale particles.To date, numerous methods have been reported for the synthesis of ZnO quantum dots composited with carbon materials. [26][27][28][29] The key problem is that some of 7 60 °C under vacuum. For comparison, the ZIF-8 and ZIF-8/CNTs within different amounts of CNTs were also prepared and characterized. The ZIF-8/CNTs composites are...

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