Supersonic cold spraying for zeolitic metal-organic framework films

We describe the first use of high-rate supersonic spray coating to deposit thin films of ZIF-8, a zeolitic metal-organic framework (MOF), adopting a sodalite architecture. This cold-spray technique is versatile and scalable, with tunable processing parameters capable of generating either a textured crystalline film or a randomly oriented polycrystalline coating on both metallic and non-metallic substrates. We provide evidence that guest occupancy by organic solvents (dimethylformamide, dimethylacetamide, and dimethylsulfoxide) in the sodalite cage of ZIF-8 structurally stabilizes the framework against high velocity impact, resulting in the preferred orientations observed. Moreover, we show that amorphous ZIF-8 films can be straightforwardly obtained at high air pressure exceeding 7 bars in which the particle velocity is 500 m/s. It is anticipated that this high-throughput approach can be adapted to fabricate microstructurally compact and strongly adhered ZIF-8 films. (C) 2016 Elsevier B.V. All rights reserved.