Flexible UiO-66-(COOH)2 metal–organic framework membranes for salinity gradient power generation

Metal-organic frameworks (MOFs) with high-density sub-nanometer pores and plenty of charged functional groups are ideal candidates for salinity gradient energy harvesting. However, synthesizing flexible and scalable MOF membranes with high performance for energy harvesting remains a challenge. Here we develop vertically aligned UiO-66-(COOH)2/polyethylene terephthalate (PET) membranes for salinity gradient energy harvesting. The PET/UiO-66-(COOH)2 membranes are fabricated by growing UiO-66-(COOH)2 crystals into nanochannels of the PET membranes via a nanoconfined interfacial growth method. The as-synthesized PET/UiO-66-(COOH)2 membranes are flexible with improved cation selectivity over PET membranes. The membranes produce a power density of 1.3 W m−2 under 0.5 M/0.01 M KCl solutions, which is better than the performances of membranes with a thickness of 10 µm. This work demonstrates that the MOFs-functionalized PET membranes with high flexibility, scalability, and ion selectivity are promising candidates for energy harvesting.