Two-dimensional electrically conductive metal-organic frameworks (MOFs) have emerged as promising model electrodes for use in electric double-layer capacitors (EDLCs). However, a number of fundamental questions about the behaviour of this...

The space industry is one of the world's fastest growing sectors. Global revenue generated from this industry is forecast to grow from 350 million USD in 2019 to more than 1 trillion USD by 2040 (Morgan Stanley, 2020). This demand stems from significantly reduced launch costs driven by commercialization (Jones, 2018), increased reliance on satellite technologies for global positioning systems, surveillance and broadband internet (Alvino et al., 2019;Dolgopolov et al., 2018;George, 2019), and postulated space resource extraction (Hein et al., 2020) and militarization (Quintana, 2017). To meet growing demand, new spaceports and launch vehicle companies are being established in historically aeronautically active nations such as the US and Russia, and in nations with emerging space sectors such as China and India (Patel, 2019;Roberts, 2019). In 2021, commercial space flights by Virgin Galactic (Gorman, 2021), Blue Origin (Johnson, 2021), and SpaceX (Wattles, 2021) demonstrated that space tourism is plausible, though the scale of this nascent industry is uncertain. Such rapid growth demands detailed understanding of the potential impact on the protective stratospheric ozone (O 3 ) layer and climate.

Metal-organic frameworks (MOFs) are among the most promising materials for next-generation energy storage systems. However, the impact of particle morphology on the energy storage performances of these frameworks is poorly...

Two-dimensional electrically conductive metal-organic frameworks (MOFs) are candidate electrode materials for use in electric double-layer capacitor (EDLC) structure-property investigations due to their well-defined crystalline structures. Their promising capacitive performance was first illustrated by EDLCs constructed with the layered framework Ni₃(HITP)₂(HITP = 2,3,6,7,10,11-hexaiminotriphenylene) and an organic electrolyte. Despite this promise, there have been few follow-up studies on the use of these frameworks in EDLCs, raising questions about the generality of the results. Here, we demonstrate the high capacitive performance of the layered framework Cu₃(HHTP)₂ (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) in EDLCs with an organic electrolyte and compare its performance with Ni₃(HITP)₂. Cu₃(HHTP)₂ exhibits a specific capacitance of 110 – 114 F g^–1at low current densities of 0.04 – 0.05 A g^–1 and shows modest capacitance retentions (66 %) at current densities up to 2 A g^–1, mirroring the performance of Ni₃(HITP)₂. However, we also explore the limitations of Cu₃(HHTP)₂ in EDLCs, finding a limited cell voltage window of 1.3 V and only moderate capacitance retention over 30,000 cycles. This illustrates that these materials require further development to improve their EDLC performance, particularly to reach similar cycling performance levels as porous carbons. Despite this, our work underscores the utility of framework materials in EDLCs and suggests that capacitive performance is largely independent of the identity of the metal node and organic linker molecule, instead being dictated by the three-dimensional structure of the framework. These important insights will aid the design of future conductive MOFs for use in EDLCs.

Metal-organic frameworks (MOFs) are among the most promising materials for next-generation energy storage systems, including supercapacitors. Few studies, however, have examined the impact of particle morphology and degree of agglomeration on the energy storage performances of these materials. To address this, here we use coordination modulation to synthesise three samples of the conductive MOF Cu3(HHTP)2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) with distinct microstructures. Evaluation of the performances of these samples in symmetric supercapacitors with organic and ionic liquid electrolytes demonstrated that samples with weakly agglomerated ‘flake-like’ particles, with short pores and many pore openings, display superior capacitive performances than samples with either weakly agglomerated ‘rod-like’ particle morphologies or strongly agglomerated ‘flake-like’ particles. The results of this study provide a target microstructure for conductive MOFs for energy storage applications.

The space industry is one of the world's fastest growing sectors. Global revenue generated from this industry is forecast to grow from 350 million USD in 2019 to more than 1 trillion USD by 2040 (Morgan Stanley, 2020). This demand stems from significantly reduced launch costs driven by commercialization (Jones, 2018), increased reliance on satellite technologies for global positioning systems, surveillance and broadband internet (Alvino et al., 2019;Dolgopolov et al., 2018;George, 2019), and postulated space resource extraction (Hein et al., 2020) and militarization (Quintana, 2017). To meet growing demand, new spaceports and launch vehicle companies are being established in historically aeronautically active nations such as the US and Russia, and in nations with emerging space sectors such as China and India (Patel, 2019;Roberts, 2019). In 2021, commercial space flights by Virgin Galactic (Gorman, 2021), Blue Origin (Johnson, 2021), and SpaceX (Wattles, 2021) demonstrated that space tourism is plausible, though the scale of this nascent industry is uncertain. Such rapid growth demands detailed understanding of the potential impact on the protective stratospheric ozone (O 3 ) layer and climate.

Two-dimensional electrically conductive metal-organic frameworks (MOFs) are candidate electrode materials for use in electric double-layer capacitor (EDLC) structure-property investigations due to their well-defined crystalline structures. Their promising capacitive performance was first illustrated by EDLCs constructed with the layered framework Ni₃(HITP)₂(HITP = 2,3,6,7,10,11-hexaiminotriphenylene) and an organic electrolyte. Despite this promise, there have been few follow-up studies on the use of these frameworks in EDLCs, raising questions about the generality of the results. Here, we demonstrate the high capacitive performance of the layered framework Cu₃(HHTP)₂ (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) in EDLCs with an organic electrolyte and compare its performance with Ni₃(HITP)₂. Cu₃(HHTP)₂ exhibits a specific capacitance of 110 – 114 F g^–1at low current densities of 0.04 – 0.05 A g^–1 and shows modest capacitance retentions (66 %) at current densities up to 2 A g^–1, mirroring the performance of Ni₃(HITP)₂. However, we also explore the limitations of Cu₃(HHTP)₂ in EDLCs, finding a limited cell voltage window of 1.3 V and only moderate capacitance retention over 30,000 cycles. This illustrates that these materials require further development to improve their EDLC performance, particularly to reach similar cycling performance levels as porous carbons. Despite this, our work underscores the utility of framework materials in EDLCs and suggests that capacitive performance is largely independent of the identity of the metal node and organic linker molecule, instead being dictated by the three-dimensional structure of the framework. These important insights will aid the design of future conductive MOFs for use in EDLCs.

Two-dimensional electrically conductive metal-organic frameworks (MOFs) have emerged as promising model electrodes for use in electric double-layer capacitors (EDLC). Here, we demonstrate the high capacitive performance of the framework Cu₃(HHTP)₂ (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) with an organic electrolyte and compare its behaviour with the previously reported analogue, Ni₃(HITP)₂ (HITP = 2,3,6,7,10,11-hexaiminotriphenylene). At low current densities of 0.04 – 0.05 A g⁻¹, Cu₃(HHTP)₂ electrodes exhibit a specific capacitance of 110 – 114 F g⁻¹ and show modest capacitance retentions (66 %) at current densities up to 2 A g⁻¹ , mirroring the performance of Ni₃(HITP)₂ and suggesting that capacitive performance is largely independent of the identity of the metal node and organic linker molecule. However, we find a limited cell voltage window of 1.3 V and only moderate capacitance retention (86 %) over 30,000 cycles at a moderate current density of 1 A g⁻¹, both significantly lower than state-of-the-art porous carbons. These important insights will aid the design of future conductive MOFs with improved performance in EDLCs.