π-Sticked Metal-Organic Monolayers for Single-Metal-Site Dependent CO2 Photoreduction and Hydrogen Evolution Reaction

Hierarchical self-assembly of 2D metal-organic layers (MOLs) for the construction of advanced functional materials have witnessed considerable interest, due to the increasing atomic utilizations and well-defined atom-property relationship. However, the construction of atomically precise MOLs with mono-/few-layered thickness through hierarchical self-assembly process remains a challenge, mostly because the elaborate long-range order is difficult to control via conventional noncovalent interaction. Herein, a quadruple pi-sticked metal-organic layer (pi MOL) is reported with checkerboard-like lattice in approximate to 1.0 nanometre thickness, on which the catalytic selectivity can be manipulated for highly efficient CO2 reduction reaction (CO2RR) and hydrogen evolution reaction (HER) over a single metal site. In saturated CO2 aqueous acetonitrile, Fe-pi MOL achieves a highly effective CO2RR with the yield of approximate to 3.98 mmol g(-1) h(-1) and 91.7% selectivity. In contrast, the isostructural Co-pi MOL as well as mixed metallic FeCo-pi MOL exhibits a high activity toward HER under similar conditions. DFT calculations reveal that single metal site exhibits the significant difference in CO2 adsorption energy and activation barrier, which triggers highly selective CO2RR for Fe site and HER for Co site, respectively. This work highlights the potential of supramolecular pi(& mldr;)pi interaction for constructing monolayer MOL materials to uniformly distribute the single metal sites for artificial photosynthesis.