Catalysis-Assisted Synthesis of Two-Dimensional Conductive Metal–Organic Framework Films with Controllable Orientation

The facile preparation of two-dimensional (2D) conductive metal-organic framework (MOF) films with controllable orientation and thickness greatly facilitates the further structure-property investigation and performance optimization in their applications. Here, we report a catalysis-assisted synthesis strategy to the rapid production of oriented films of catechol-based (Cu3(HHTP)2, Zn3(HHTP)2, and Cu2TBA) and diamine-based (Ni3(HITP)2) 2D conductive MOFs with thicknesses adjustable from tens of nanometers to several micrometers. Relying on the utilization of a 0.3 nm Pt layer, which can be conveniently predecorated on a substrate surface via evaporating deposition or sputtering, as a catalyst for the aerobic oxidation of the redox-active ligands to trigger the formation of 2D conductive MOFs, this strategy is compatible with a majority of commonly used substrates and capable of producing patterned films with feature sizes ranging from micrometers to centimeters. Investigation on the growth kinetics of Cu3(HHTP)2 indicates that the preferential growth along the c-axis or in the ab-basal plane of its crystallites can be flexibly tuned by the formation reaction kinetics to guide the evolution of films with the face-on or edge-on orientation. The chemiresistive device incorporating the face-on Cu3(HHTP)2 film presents a high response (197%) and a fast respond speed (27 s) toward NH3 (30 ppm) at room temperature, which are superior not only to its edge-on counterpart (90% and 69 s, correspondingly) but also to other reported Cu3(HHTP)2-based sensors.