Mapping\nthe Nexus of Electrical Conductivity and Gas\nSensing for Tailored Design of Transition Metal (Cu, Co, Ni)-Based\nBimetallic 2D Conjugated MOF

Bimetallic 2D π-conjugated HHTP metal–organic\nframeworks\n(2D <i>c</i>-HHTP-MOFs), which with improved electrical\nconductivity, extended active sites, and customizable band gaps, have\nattracted a greater interest than their monometallic counterparts\nin electronics. However, there is no study on engineering bimetallic\n2D <i>c</i>-HHTP-MOFs containing tunable 3<i>d</i> transition metal units in the field of chemiresistive sensors yet.\nHere, we present a mapping of electrical conductivity–gas sensing\nthat enables the creation of bimetallic 2D M/Cu-HHTP <i>c</i>-MOFs (M = Co, Ni) with tailored metal nodes. We used crystal structure\nrefinement, density functional theory (DFT) calculations, <i>in situ</i> diffuse reflectance infrared Fourier transform spectroscopy\n(<i>in situ</i> DRIFT), and conductivity measurements to\nexplore the role of metal nodes in the topology structure, ammonia\n(NH<sub>3</sub>) adsorption capacity, energy band structure, and electrical\nconductivity. Consequently, we show that designing 2D Co/Cu-HHTP <i>c</i>-MOFs with both enhanced gas sensing and high electrical\nconductivity (σ ≈ 1.50 × 10<sup>–3</sup> S·cm<sup>–1</sup>) can be applied in constructing high-performance\nroom-temperature NH<sub>3</sub> chemiresistor, exhibiting higher sensitivity,\nbetter selectivity, reduced baseline resistance drift (<10%), and\nmore superior repeatability and stability, compared with reported\nmonometallic powdered 2D <i>c</i>-HHTP-MOFs. This work paves\nthe way for designing high catalytic activity of bimetallic 2D <i>c</i>-MOFs without compromising their electrical conductivity.