Facile synthesis of nanoscale high porosity IR-MOFs for low-k dielectrics thin films

• Nanoscale IR-MOFs are synthesized by the improved coordination modulation method.
• Zinc acetate provides a zinc source, adjusts the pH, and acts as capping agent.
• IR-MOF films on ITO glass are formed by dipping-coating-secondary-growth.
• IR-MOF films have low k values, good mechanical strength and hydrophobicity.

To explore the preparation of ultra-low k MOFs material, uniform nanosized isoreticular metal−organic frameworks (IR-MOFs) nanocrystals were prepared by the optimized coordination modulation method and the IR-MOF nanocrystals were used to form IR-MOF films on an ITO glass by dip coating and secondary growth. The continuous thin MOF-3, MOF-5 and MOF-10 films supported on ITO glass had a dielectric constant of 1.2, 2.1 and 4.8 at 2 MHz respectively, and good mechanical strength, adhesion, and hydrophobicity. However, probably due to the presence of the strong polarity of NH2-BDC in MOF-3, and the presence of N–H moieties on grain boundaries, crystal surfaces, and internal crystal defects, which abundantly adsorb water, the MOF-3 film has higher low-k at 100 kHz. For the MOF-10 film with high low-k at 100 kHz, due to the low BET surface area, it could be related to the strong polarity of solvent molecular trapped in the films.

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