Fabrication of shrinkage-free poly(ether ether ketone) nanofibrous mat and its use for flexible and thermally-recycled MOF composites

Abstract Electrospinning has provided a simple and useful technique for producing nanofibrous structures that emerge with versatile properties and functions. However, the shape instability (i.e., shrinkage) is always a common falling of conventionally-electrospun fibers when applying in harsh conditions. In this work, fabrication of shrinkage-free nanofibrous mats of poly(ether ether ketone) (PEEK) that has excellent properties was successfully realized through a delicate strategy consisted of three steps of coaxial electrospinning, annealing at low temperature and removal of the outer sheath. PEEK was first nanosized within polyester sheath in solution state, then deep phase separation progressed to form dense nanofibers with high crystallinity at low temperature. After removal of sheath, the nanofibrous PEEK mats displayed good mechanical properties and excellent shape stability against heating. Consequently, the PEEK mats were used as the substrate for depositing MIL-53(Al), a kind of metal-organic frameworks (MOFs), at elevated temperature to prepare free-standing and flexible composite mats. The obtained composite mats revealed considerable affinity and high load of MIL-53(Al) with PEEK nanofibers. PEEK/MIL-53(Al) composite mats were used as absorbent and showed almost equally effective absorption capacity of methylene blue (MB) from aqueous solution as powdered MOF, while the composite mats were easily regenerated through thermal treatment.