Highly Hydrophobic and Chemically Rectifiable Surface-Anchored Metal-Organic Framework Thin-Film Devices

Functionalizing various surfaces with metal-organic frameworks (SURMOFs) are promising platforms for a variety of technological applications. Herein, liquid-phase epitaxy has been employed to grow oriented and uniform SURMOF thin-films of Cu ion and tetracyanoquinodimethane (TCNQ) ligand on self-assembled monolayer templates. The SURMOF thin-films of Cu-TCNQ on fluorine doped tin oxide, Au, and polyethyleneterephthalate substrates are realized to be highly hydrophobic exhibiting contact angle of water approximate to 140 degrees. SURMOF thin-film devices of Cu-TCNQ have been fabricated by employing electron-beam lithography technique. Room-temperature current-voltage (I-V) characteristics consistently showed non-Ohmic semiconductivity in the range of approximate to 10(-5) S cm(-1). A remarkable rectification in the electrical conductance of SURMOF thin-film device with rectification factor of approximate to 100 was achieved upon exposing iodine (I-2) vapor at ambient conditions whereas bulk-Cu-TCNQ remains nonrectified. Even, highly hydrophobic surface nature is retained in course of gaining electrical rectification. The unusual rectifying thin-film phenomenon induced by I-2 is attributed to structural and electronic reorganization in the SURMOF and the rectification follows standard Shockley diode equation. The here presented results demonstrate a new avenue of research on MOFs where electronic and magnetic properties in particular can be efficiently explored and controlled in SURMOF thin-film device configurations (also mechanically flexible) for various technological applications.