2D Rhodium-Isocyanide Frameworks

Abstract

2D metal-organic frameworks (2D MOFs) are emerging organic van der Waals materials with great potential in various applications owing to their structural diversity, and tunable optoelectronic properties. So far, most reported 2D MOFs rely on metal-heteroatom coordination (e.g., metal-nitrogen, metal-oxygen, and metal-sulfur); synthesis of metal-carbon coordination based 2D MOFs remains a formidable challenge. This study reports the rhodium-carbon (Rh-C) coordination-based 2D MOFs, using isocyanide as the ligand and Rh(I) as metal node. The synthesized MOFs show excellent crystallinity with quasi-square lattice networks. These MOFs show ultra-narrow bandgaps (0.1-0.28 eV) resulting from the interaction between Rh(I) and isocyano groups. Terahertz spectroscopy demonstrates exceptional short-range charge mobilities up to 560 ± 46 cm² V^-1 s^-1 in the as-synthesized MOFs. Moreover, these MOFs are used as electrocatalysts for nitrogen reduction reaction and show an excellent NH₃ yield rate of 56.0 ± 1.5 µg h^-1 mg_cat ^-1 and a record Faradaic efficiency of 87.1 ± 1.8%. In situ experiments reveal dual pathways involving Rh(I) during the catalytic process. This work represents a pioneering step toward 2D MOFs based on metal-carbon coordination and paves the way for novel reticular materials with ultra-high carrier mobility and for versatile optoelectronic devices.

Keywords: 2D; carrier mobility; isocyanide; metal‐organic framework; rhodium.