Copper(II)-Doped Two-Dimensional Titanium-Based Metal-Organic Frameworks toward Light-Driven CO Reduction to Value-Added Products.

Recently, metal-organic framework (MOF)-based photocatalysts for an efficient CO reduction reaction have drawn wide attention in multidisciplinary fields and sustainable chemistry. In this work, a series of Cu-doped two-dimensional Ti-based MOFs were fabricated by a facile in situ solvothermal method. Cu ions were doped in equal proportions and uniformly dispersed in the crystal structure of the MOF matrix. Interestingly, the doping content of Cu ions and the photocatalytic performance displayed an obvious volcanic relationship, the medium-concentration Cu-doped sample (T1-2Cu) held the greatest activity with 100% carbonaceous product (CH and CO) formation, and the CH production rate was 3.7 μmol g h with 93% electron selectivity. The band structure, local electronic structure, carrier separation kinetics, and CO adsorption studies demonstrated that the excellent photocatalytic activity of T1-2Cu benefited from the appropriate amount of Cu ion doping: (1) a doping amount of 2 atom % optimized the conduction band position of the MOF substrate and endowed T1-2Cu with strong reduction potential in thermodynamics, (2) doping Cu ions tuned the local electronic environment around titanium oxide clusters and optimized the generation, separation, and migration processes of photoinduced carriers, and (3) the introduction of Cu ions also provided more accessible active sites and more probabilities for the adsorption and activation of CO reactants.