New Approach for Synthesizing Metal Organic Frameworks on Surfaces

Novel strategy leads to improved control of material growth

Metal-organic frameworks (MOFs), a class of porous nanomaterials composed of metal ions linked together by organic ions or molecules, exhibit tunable properties that make them promising for a range of applications such as sensing, catalysis, and drug delivery. In order to exploit their potential, researchers have focused on synthesizing MOFs on reactive surfaces. This process allows for the integration of MOFs directly onto readout components for practical use. Semih Sevim from the deMello group and collaborators have taken the next step in the controlled synthesis of MOFs on surfaces by developing a novel strategy that implements microfluidics.

A wide variety of methods have been used for integrating MOFs onto surfaces. Although many successful results have been shown, controlled synthesis of MOF gradients onto precise locations within a surface remains challenging. By employing a continuous-flow microfluidics device over a reactive surface, Semih demonstrated the production of such surfaces with regions of different MOF compactness.

Semih leveraged the diffusion-dominant behavior of laminar flow conditions in microfluidics to synthesize HKUST-1, an extensively studied MOF with multiple practical applications. One inlet was loaded with the HKUST-1 reactant (H3BTC) while a second inlet contained an unreactive solution (ethanol). By concurrently increasing the flow rate of the H3BTC solution and decreasing the flow rate of ethanol over time, the reactive material underneath the microfluidic device experienced varying exposure times to the HKUST-1 synthesis reaction (see picture). HKUST-1 was produced only when the surface was exposed to the H3BTC solution. This novel strategy generated a material with progressively decreasing compactness of HKUST-1 on its surface. Accordingly, Semih’s work demonstrated that microfluidics is a promising tool to controllably synthesize MOF gradients onto surfaces with tailor-made designs. This ability has the potential to unlock fabrication of other MOFs with gradients and new MOF-based devices.

Written by Jeff Hsiao.

Read the full paper here.

Progressively increasing the flow rate of H3BTC and decreasing the flow rate of ethanol over time leads to varying exposure times of the surface to the HKUST-1 synthesis reaction.

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