Light‐Enhanced Osmotic Energy Harvester Using Photoactive Porphyrin Metal–Organic Framework Membranes

Abstract

High ion selectivity and permeability, as two contradictory aspects for the membrane design, highly hamper the development of osmotic energy harvesting technologies. Metal–organic frameworks (MOFs) with ultra‐small and high‐density pores and functional surface groups show great promise in tackling these problems. Here, we propose a facile and mild cathodic deposition method to directly prepare crack‐free porphyrin MOF membranes on a porous anodic aluminum oxide for osmotic energy harvesting. The abundant carboxyl groups of the functionalized porphyrin ligands together with the nanoporous structure endows the MOF membrane with high cation selectivity and ion permeability, thus a large output power density of 6.26 W m−2 is achieved. The photoactive porphyrin ligands further lead to an improvement of the power density to 7.74 W m−2 upon light irradiation. This work provides a promising strategy for the design of high‐performance osmotic energy harvesting systems.

Light‐Controlled Ionic/Molecular Transport through Solid‐State Nanopores and Nanochannels

“…The first type is the salinity gradient energy conversion (blue energy) with ion passive transport. [210][211][212] The other type is based on the solar energy harvesting with active ion transport. [65] The optoelectronic modulation is of great importance for improving the performance by using the two types of the nanofluidic systems.…”

“…According to the different types of the ion transport, whether it is passive or active, the ion transport‐based energy conversion can be generally divided into two categories. The first type is the salinity gradient energy conversion (blue energy) with ion passive transport [210–212] . The other type is based on the solar energy harvesting with active ion transport [65] .…”

Maximizing Ion Permselectivity in MXene/MOF Nanofluidic Membranes for High‐Efficient Blue Energy Generation

“…[ 17 ] The precise angstrom‐sized channels provide ideal confined space that shows significant advantage for ultrahigh ion selectivity owing to the high overlapping degree of electric double layer (EDL) and the dehydration effect of hydrated ions caused by the ultra‐small pores of the MOF. [ 18,12 ] However, considering the difficulty in independent film formation and the scarcity of surface charge density of MOF itself, MOF are usually composited with other materials to form hybrid membranes [ 19 ] For example, porphyrin MOF was electrochemically deposited onto anodized aluminum (AAO) to prepare heterogeneous membrane for osmotic power harvesting. [ 18 ] However, the output power density of the MOF‐based composite membrane has not yet reached the commercialization benchmark (5 W m −2 ), suffering from the limited ion permeability and selectivity.…”

“…[ 18,12 ] However, considering the difficulty in independent film formation and the scarcity of surface charge density of MOF itself, MOF are usually composited with other materials to form hybrid membranes [ 19 ] For example, porphyrin MOF was electrochemically deposited onto anodized aluminum (AAO) to prepare heterogeneous membrane for osmotic power harvesting. [ 18 ] However, the output power density of the MOF‐based composite membrane has not yet reached the commercialization benchmark (5 W m −2 ), suffering from the limited ion permeability and selectivity. [ 20 ] Therefore, a new hybridization strategy is required to generate hybrid membranes such as, integrating MOF into MXene membranes for improving both the ion permeability and selectivity.…”

Photo-controllable Ion-Gated Metal–Organic Framework MIL-53 Sub-nanochannels for Efficient Osmotic Energy Generation

“…In nature, the precise control of the opening and closing of ion channels is essential for ion transport and the regulatory functions of living cells. , For instance, under ambient stimuli, ion channels in electric eels can be quickly opened from the closed state to realize high selectivity and ultrafast transport of Na + and K + ions, which can convert ionic gradient energy to high-voltage electricity. , Researchers have constructed various smart ion-gating nanochannels to imitate the excellent ion selectivity and switching property of biological ion channels, which not only provide a platform for simulating the ion transport process in organisms but also promote the practical application of smart ion-gating nanochannels in the nanofluid, nanofiltration, and energy conversion fields. − In particular, eel-inspired nanochannels for controllable osmotic power harvesting show great potential due to their easy availability and widespread mixing of river water with seawater. − …”