Epitaxial Electrodeposition of Cu-BTC Metal-Organic Framework Thin Films onto the (100), (110), and (111) Surfaces of Single-Crystal Gold and Cuprous Oxide Buffer Layers.

Metal-organic frameworks (MOFs) have well-defined pore structures. Epitaxial MOFs can produce films with uniform pore sizes and open porosity. However, the growth of epitaxial MOF thin films has remained a challenge. Herein, we demonstrate a cathodic electrodeposition method for the epitaxial growth of a well-known MOF material, copper(II)-benzene-1,3,5-tricarboxylate (Cu-BTC), from solution precursors. The epitaxial electrodeposition of Cu-BTC was achieved in a Cu(NO3)2-H3BTC-H2O2 bath using H2O2 reduction to deprotonate the H3BTC molecule. The Cu-BTC films can be grown to micrometer thicknesses with Faradaic efficiencies up to 94%. Three different crystal orientations of epitaxial Cu-BTC thin films can be obtained with different substrates. The films are deposited onto the (100), (110), and (111) surfaces of single-crystal Au and Cu2O buffer layers. Epitaxial Cu-BTC(100) grows on Au(100) with a single in-plane domain with a parallel relationship with respect to Au(100) and a coincidence site lattice (CSL) mismatch of +1.11%. Epitaxial Cu-BTC(111) is deposited on epitaxial Cu2O/Au(111) with a single in-plane domain with an antiparallel relationship with respect to Cu2O(111) and a CSL mismatch of -0.91%. Twinned films of epitaxial Cu-BTC (110) are produced on Cu2O/Au(110) with a CSL mismatch of +0.12%. Epitaxial Cu-BTC(100) provides oriented square-shaped nanochannels with a 9 Å aperture, and epitaxial Cu-BTC(111) has oriented tetrahedral-shaped side pockets with triangular windows of an internal diameter of 3.5 Å.