Layer-by-Layer 2D Ultrathin Conductive Cu-3(HHTP)(2) Film for High-Performance Flexible Transparent Supercapacitors

2D conductive metal-organic frameworks (2D c-MOFs) naturally possess high active sites, large specific surface areas, and fast ion transport for energy-storage devices. However, the intelligent exploration of 2D c-MOFs for the emerging flexible transparent supercapacitors (FTSCs) with excellent photoelectric property and electrochemical activity is rarely implemented. Herein, 2D conductive ultrathin Cu-3(HHTP)(2) (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) film is synthesized on the indium tin oxide/polyethylene terephthalate (ITO/PET) substrate for flexible transparent conductive electrodes (FTCEs) through the layer-by-layer assembly method. The interconnected conductive frameworks possess the cooperative superiority of low internal resistance, fast electrolyte ion diffusion, and quick electron transfer. Cu-3(HHTP)(2)-15/ITO/PET FTCEs show high photoelectric property of T-550 nm = 82.2% and R-s = 49.1 omega sq(-1), and high areal capacitance (C-A) of 1700 mu F cm(-2). The corresponding symmetrical FTSCs (T-550 nm = 62.1%) exhibit excellent C-A of 939.2 mu F cm(-2) at the current density of 7 mu A cm(-2), superior rate capability (63.9% at 150 mu A cm(-2)), long-term cycling stability (85% after 3000 cycles), and mechanical flexibility under different bending angles. This work provides key insights into the design and synthesis of 2D c-MOF films for flexible transparent energy-storage devices.