Conventional solvothermal synthesis to produce MOFs typically involves harsh conditions and consumes hours to days for a batch process. Consequently, these disadvantages hinder MOF industrial implementation and expansion of potential MOF applications. Rapid synthesis methods at mild conditions are therefore highly desired for MOFs.
We find ZnO can accelerate the synthesis of HKUST-1 (Cu3(BTC)2) at room temperature. HKUST-1 space-time-yield reaches up to 2.9×104 kg∙m-3∙d-1, which is over 10× higher than previous reports. Powder XRD and BET analysis confirm the formation of crystalline HKUST-1 with surface area of 1874±73 m2/g. We investigated the reaction mechanism using STEM-EDX, XRD and FTIR, and the results suggest hydroxyl double salt ((Zn,Cu)(OH)3NO3) is an important intermediate to drive the rapid formation of HKUST-1. ICP-OES shows the concentration of Zn residue in the MOF product is generally less than 0.70 wt%, and that n(Zn):n(Cu) in the filtrate collected after the rapid synthesis is larger than the initial molar ratio in the mixed reactants. These results all indicate ZnO is consumed and converted into soluble Zn-containing species during the rapid synthesis.
Using the same synthesis strategy, we deposited ZnO thin films via atomic layer deposition (ALD) onto polymer spheres, silicon wafers and fibrous substrates for growing HKUST-1 coatings. MOF patterns were also obtained on pre-patterned ZnO surfaces. We will discuss how MOF-functionalized fibrous materials can be used for hazardous gas mitigation. This rapid room-temperature approach is also promising for applications such as membrane separation and chemical sensing.