A two-dimensional (2D) copper tetra-(4-carboxyphenyl) porphyrin (Cu-TCPP) nanosheet-based nanofluidic membrane was developed for efficient ionic energy harvesting. The membrane exhibits ultrahigh ion permeability and a power density of 16.64 W m⁻² under artificial seawater/river water conditions, surpassing state-of-the-art nanochannel membranes. The Cu-TCPP membrane's inherent photothermal properties enable light-controlled ion transport, even under natural sunlight. By combining solar energy with salinity gradients, the driving force for ion transport is enhanced, leading to improved energy conversion performance. Notably, light can eliminate the need for salinity gradients, achieving a power density of 0.82 W m⁻² in a symmetric solution system. The Cu-TCPP membrane demonstrates exceptional ion selectivity and permeability, with a high power density of 31.92 W m⁻² under light irradiation. The membrane's unique structure and photothermal properties enable efficient ionic energy conversion, extending the concept of salinity energy to ionic energy. The Cu-TCPP membrane also shows excellent stability and scalability, with a large-scale membrane area of 78.5 cm². The membrane's performance was further validated through various experiments, including light-assisted ion transport and energy conversion under different conditions. The Cu-TCPP membrane's potential for practical applications in osmotic energy harvesting is highlighted, with the ability to generate significant power densities under various conditions. The study demonstrates the feasibility of ionic energy conversion in equilibrium electrolyte solutions without salinity gradients, opening new possibilities for the recovery of ionic and light energy from diverse saline resources.A two-dimensional (2D) copper tetra-(4-carboxyphenyl) porphyrin (Cu-TCPP) nanosheet-based nanofluidic membrane was developed for efficient ionic energy harvesting. The membrane exhibits ultrahigh ion permeability and a power density of 16.64 W m⁻² under artificial seawater/river water conditions, surpassing state-of-the-art nanochannel membranes. The Cu-TCPP membrane's inherent photothermal properties enable light-controlled ion transport, even under natural sunlight. By combining solar energy with salinity gradients, the driving force for ion transport is enhanced, leading to improved energy conversion performance. Notably, light can eliminate the need for salinity gradients, achieving a power density of 0.82 W m⁻² in a symmetric solution system. The Cu-TCPP membrane demonstrates exceptional ion selectivity and permeability, with a high power density of 31.92 W m⁻² under light irradiation. The membrane's unique structure and photothermal properties enable efficient ionic energy conversion, extending the concept of salinity energy to ionic energy. The Cu-TCPP membrane also shows excellent stability and scalability, with a large-scale membrane area of 78.5 cm². The membrane's performance was further validated through various experiments, including light-assisted ion transport and energy conversion under different conditions. The Cu-TCPP membrane's potential for practical applications in osmotic energy harvesting is highlighted, with the ability to generate significant power densities under various conditions. The study demonstrates the feasibility of ionic energy conversion in equilibrium electrolyte solutions without salinity gradients, opening new possibilities for the recovery of ionic and light energy from diverse saline resources.