Biomimetic low-porosity framework membranes for efficient power generation and acid recycling from industrial...

Selective proton transport membranes are crucial for applications like fuel cells, acid recycling, and osmotic power generation, but their rational construction to achieve both high selectivity and permeability is challenging. Biological proton channels demonstrate exceptional performance owing to their nonporous structure, which lacks open pathways for ions but contains a hydrogen-bonding network for fast proton hopping, distinct from artificial membranes featuring open pores. Inspired by this, we intentionally designed an amorphous phosphated covalent organic framework (COF) membrane with low porosity. Unlike conventional COFs, this membrane exhibits no measurable gas adsorption and blocks metal ion transport. Meanwhile, its phosphonic acid groups form a continuous hydrogen-bonding network that enables efficient proton hopping. As a result, the proton permeation rate reached 1.94 mol m^-2 h^-1, comparable to that of the biological proton channels, with a selectivity over 10³ against heavy metal ions. This combination allows the membrane to stably recycle acid from industrial waste acid while preventing heavy metal leakage. It also generates osmotic power from this process, reaching a power density far exceeding previous osmotic power generation membranes. This work sheds light on the simultaneous matter and energy extraction process to enable negative-carbon wastewater treatment and utilization.