Direct synthesis of two-dimensional Cu₃(C₆O₆) kagome conjugated coordination polymer thin films via chemical vapor...

Chemical vapor deposition (CVD) is a promising route for device-compatible two-dimensional (2D) conjugated coordination polymer (c-CP) thin films, but control of the coordination environment during growth remains underdeveloped. Here, we report the direct CVD synthesis of 2D kagome Cu₃(C₆O₆) c-CP thin films using Cu(tBuacac)₂ (tBuacac = tert-butylacetoacetate) as a rationally selected metal precursor. To avoid the THQ-pillared framework previously obtained from Cu(acac)₂, in which kagome c-CP layers are separated by axial THQ ligands, we used the bulkier Cu(tBuacac)₂ precursor to modulate the coordination pathway during CVD growth. Time-dependent ex situ GIWAXS analysis showed no reflections associated with the THQ-pillared framework during synthesis, due to suppression of axial THQ coordination and the direct growth of face-on layered Cu₃(C₆O₆). GIWAXS, HRTEM, Raman, XPS, and FT-IR analyses also support the formation of the layered Cu₃(C₆O₆) c-CP structure. The Cu₃(C₆O₆) thin film exhibited an optical bandgap of ∼1.29 eV and a room-temperature conductivity of ∼0.10 S cm^-1. This work demonstrates that metal precursor geometry is important for modulating the coordination pathway during CVD growth and provides an effective strategy for accessing targeted c-CP thin films.