In-situ growth of metal-organic frameworks in a reactive 3D printable material

The additive manufacturing (3D printing) of porous materials will open unprecedented opportunities to design advanced supports for extraction and separation. Here we have fabricated a reactive ZnO nanoparticle (NP)/thermoplastic composite filament for 3D printing via fused deposition modeling. The composite filament contains a 10 wt% ZnO-NPs incorporated in the thermoplastic acrylonitrile butadiene styrene (ABS). After 3D printing with the ZnO-NP/ABS filament, crystals of the zeolitic imidazolate framework-8 (ZIF-8) are grown in-situ on the 3D printed part. In-situ ZIF-8 crystallization is achieved by a mild chemical conversion mechanism at room temperature, converting the embedded ZnO nanoparticles into ZIF-8 crystals which are subsequently expressed on the surface of the 3D printed device. The resulting ZIF-8@ZnO-NP/ABS 3D printed devices were applied to the extraction of malachite green as a model water pollutant, and delivered superior performance compared with an identical device made of pure ABS, or the precursor ZnO-NP/ABS. For comparison purposes, a ZIF-8/ABS filament was fabricated with a 10 wt% load of presynthesized ZIF-8 crystals. The in-situ ZIF-8 growth approach again showed enhanced extraction performance in comparison with materials directly loaded with ZIF-8 crystals, with an increase of 48% in the extraction of malachite green. This is the first example of ZnO to ZIF-8 chemical conversion on 3D printed devices.