High-Temperature Proton Conduction in Covalent Organic Frameworks Interconnected with Nanochannels for Reverse Electrodialysis

Abstract

The crystalline porous organic framework offers a highly ordered and stable structure under hydrated conditions at high temperatures. Here, we demonstrated a method for preparing high-performance membrane buildup using “heterogeneous networks” and “polymer phase-separated nanochannels”. A well-interconnected “nanochannel” with a “crystalline organic framework” forms a highly stable hybrid membrane above 80 °C under 100% hydration under acidic and basic conditions. The prepared structure provides a self-standing membrane that easily overcomes the problem faced by conventional high ion-exchange capacity (IEC)-based membranes such as swelling, gelling, fragility, and dissolving at elevated temperatures. Apart from structural stability, it also shows better chemical stability with enhanced proton conduction at elevated temperatures. This proton conduction with better structural stability in the high IEC sample confirms from thermal analysis, whereas it also offers relatively low in-plane membrane swelling as compared to the conventional membranes. These hybrid membranes were further combined with the FAA-3 membrane to manufacture a reverse electrodialysis system for generating a power output. We also evaluated the maximum power density (P max) of the stack theoretically and experimentally. The determined net power density (P net) is reported to be 0.45 W m–2 at a flow rate of 40 mL min–1. These results confirm that the developed membrane can withstand robustly under realistic ambient conditions maintaining stable cell performance.

Giant Osmotic Energy Conversion through Vertical-Aligned Ion-Permselective Nanochannels in Covalent Organic Framework Membranes

“…Covalent organic frameworks (COFs) are a class of crystalline porous materials assembled using molecular building units featuring predetermined and atomically ordered channel architectures. − COF membranes have previously been applied to precise molecular/ion transport − and energy-related applications. − Here, we demonstrate high-performance osmotic energy conversion membranes based on oriented 2D COFs that allow us to precisely control nanochannel orientation and functionality simultaneously, thereby achieving high ion permeability and selectivity. Our approach combines (1) the use of oriented 2D COF membranes to provide densely packed (pore density: ∼10 13 cm –2 ) vertically aligned one-dimensional nanofluidic channels and (2) the surface-engineering strategy to incorporate functional groups (e.g., sulfonate and quaternary ammonium groups) that can be used to manipulate the channel wall charge polarity and density.…”

Sulfonated Polyphosphazene-Blended Self-Cross-Linked Polybenzimidazole-Based High-Temperature Proton Exchange Membranes: High Efficiency in Proton Transport at Low Humidity

“…They corresponded to exothermic DSC peaks. For the SPNPP sample, a weight loss of 35.62% occurred at 200–425 °C, which was ascribed to desulfurization . The weight loss of cCM-mPBI/SPNPP samples was evidently less than those of CM-mPBI and SPNPP.…”

“…For the SPNPP sample, a weight loss of 35.62% occurred at 200−425 °C, which was ascribed to desulfurization. 43 The weight loss of cCM-mPBI/SPNPP samples was evidently less than those of CM-mPBI and SPNPP. It was mainly because the self-covalent cross-linking between CM-mPBI formed three-dimensional structures.…”

Integrating Ordered Two-Dimensional Covalent Organic Frameworks to Solid-State Nanofluidic Channels for Ultrafast and Sensitive Detection of Mercury

“…42−44 However, 2D COFs nanochannels always suffer from difficult thickness control and poor mechanical stability. 45 The artificial anodic aluminum oxide nanochannel (AAO) is well known for its good mechanical and chemical stability. 46 Therefore, the integration of 2D COFs with AAO seems promising for the fabrication of nanofluidic sensors for rapid and sensitive detection but, to the best of my knowledge, has not been explored so far.…”

“…The crystalline covalent organic frameworks (COFs) with large specific surface area, permanent pores, and ordered structure are well known with rapid kinetics for the interaction with analyte. , The inherent ordered channels make two-dimensional (2D) COFs promising as nanofluidic channels. Recently, the nanochannels of a few 2D COFs have been applied in bio-sensing, enantiomer separation, and water desalination. − However, 2D COFs nanochannels always suffer from difficult thickness control and poor mechanical stability . The artificial anodic aluminum oxide nanochannel (AAO) is well known for its good mechanical and chemical stability .…”