Metal-organic frameworks (MOFs) containing redox active linkers have led to hybrid compounds exhibiting high electrical conductivity, which enables their use in applications in electronics and electrocatalysis. While many computational studies predict two-dimensional (2D) MOFs to be metallic, the majority of experiments show decreasing conductivity on cooling, indicative of a gap in the electronic band structure. To date, only a handful of MOFs have been reported that exhibit increased electrical conductivity upon cooling indicative of a metallic character, which highlights the need for better understanding the origin of the conductivity. A 2D MOF containing iron bis(dithiolene) motifs was recently reported to exhibit semiconducting behavior with record carrier mobility. Herein, we report that high crystallinity and the elimination of guest species results in an iron 2,3,6,7,10,11-tripheylenehexathiolate (THT) MOF, FeTHT, exhibiting a complex transition from semiconducting to metallic upon cooling, similar to what was shown for the analogous CoTHT. Remarkably, exposing the FeTHT to air significantly influences the semiconducting-to-metallic transition temperature (100 to 300 K), and ultimately results in a material showing metallic-like character at, and above, room temperature. This study indicates these materials can tolerate a substantial degree of doping that ultimately results in charge delocalization and metallic-like conductivity, an important step towards enabling their use in chemiresistive sensing and optoelectronics. carriers, preventing fast charge transport through the framework. This leads to materials with insulating or large gap semiconducting behavior. 5,14,15 Efforts to reduce the barriers to charge transport have included the addition of guest species, [16][17][18] doping, [19][20][21] and variation of the metal center and its oxidation state. [22][23][24][25][26] These modifications can encourage through-space 27,28 or throughbond 29 electronic transport and have led to MOFs with improved conductivities, with one example reporting tunable conductivity over six orders of magnitude. 17 Recently, the development of MOFs with redox active linkers has led to a breakthrough in the field of electrically conductive MOFs. 11,12,15,[30][31][32][33][34] Several two-and three-dimensional (2D/3D) frameworks with planar, π-conjugated, and redox-active linkers, like semiquinones/cathecolates, [35][36][37][38][39][40][41][42][43] diimines, [44][45][46][47][48] and dithiolenes, 19,21,[48][49][50][51][52][53][54][55][56][57][58][59][60][61] have been reported to display high electrical conductivity. Yet, while computational studies often predict these 2D MOFs to be metallic, 50,[62][63][64][65] the majority of the frameworks reported display a decrease in conductivity on cooling as thermally-populated carriers are lost. In contrast, the primary mechanism for carrier scattering in metals is due to lattice vibrations that are significantly dampened at lower temperatures, resulting in more efficient transport o...

The reduction of CO2 into higher energy products such as carbon-based fuels and feedstocks is an attractive strategy for mitigating the continuous rise in CO2 emissions associated with the growing global energy demand.