Fluorinated metal-organic framework as bifunctional filler toward highly improving output performance of triboelectric nanogenerators

Triboelectric nanogenerators (TENGs) with high power-generating performance always attract much attention as one emerging green energy technology. To pursue higher triboelectricity of triboelectric materials and improve output performance of TENGs, various nano/micro-materials with high charge-trapping capabilities were introduced into TENGs as fillers, but challenges remained in single functionality of the fillers. Herein, an unconventional filler, fluorinated metal-organic framework (F-MOF), with bifunctionality (both high charge-inducing and charge-trapping capabilities) was incorporated into polydimethylsiloxane (PDMS) matrix to highly improve negative triboelectricity, charge-trapping property and hydrophobicity of composite films. With such an optimized composite film and an Al foil as the triboelectric pair, TENGs were assembled and showed an 11-time increase in the output power density. The working mechanism of the F-MOF in the composite film was discussed through elaborate experimental and theoretical analysis. Besides, F-MOF fillers also worked well when other polymer matrices (Poly(vinylidene fluoride), (PVDF) silicone rubber (Si- rubber), Polytetrafluoroethylene (PTFE), Polyurethane (PU) and Polyacrylonitrile (PAN))were used as the substitutes for PDMS, proving that the F-MOF can be used as the universal filler for improving output performance of TENGs. The successful attempt to introduce MOF as a filler paved a promising way to enhance the output performance of TENGs and enlarge the materials pool to choose for TENGs.