Mesoporous Bimetallic MOF for Efficient Mechanical Energy Harvesting in PVDF

Flexible mechanical energy harvesting using poly(vinylidene fluoride) (PVDF) is a promising route toward self-powered wearable and IoT systems. However, the limited electroactive phase content of pristine PVDF restricts its performance. In this work, we investigate the influence of Co-, Ni-, and CoNi-metal−organic framework (MOF) fillers on the electromechanical properties of PVDF. Monometallic Co- and Ni-based MOFs and a bimetallic CoNi-MOF with a benzene-1,4-dicarboxylate linker were synthesized and incorporated into PVDF to form flexible composite films. Owing to its highly exfoliated 2D morphology, large accessible surface area, favorable mesoporous structure, and possible bimetallic synergy, the CoNi-MOF enables strong interfacial coupling with PVDF chains, leading to a substantial enhancement of electroactive phases. An optimal CoNi-MOF loading of 3 wt % in PVDF yields the highest polar phase fraction (∼88%) and a superior electromechanical response. Mechanical energy harvesters fabricated from this composite deliver an open-circuit voltage of ∼26 V, a short-circuit current of ∼7 μA, and a peak power density of ∼15 μW/cm2. The device further exhibits excellent dynamic and static pressure sensitivity, efficient capacitor charging, and effective harvesting of biomechanical energy from human motions. These results demonstrate that the investigated CoNi-MOF is an effective filler for high-performance PVDF-based mechanical energy harvesting and self-powered sensing applications.