Copper(II)-Doped Two-Dimensional Titanium-Based Metal–Organic Frameworks toward Light-Driven CO2Reduction to Value-Added Products

Recently, metal–organic framework (MOF)-based photocatalysts for an efficient CO 2 reduction reaction have drawn wide attention in multidisciplinary fields and sustainable chemistry. In this work, a series of Cu 2+ -doped two-dimensional Ti-based MOFs were fabricated by a facile in situ solvothermal method. Cu 2+ ions were doped in equal proportions and uniformly dispersed in the crystal structure of the MOF matrix. Interestingly, the doping content of Cu 2+ ions and the photocatalytic performance displayed an obvious volcanic relationship, the medium-concentration Cu 2+ -doped sample (T1-2Cu) held the greatest activity with 100% carbonaceous product (CH 4 and CO) formation, and the CH 4 production rate was 3.7 μmol g –1 h –1 with 93% electron selectivity. The band structure, local electronic structure, carrier separation kinetics, and CO 2 adsorption studies demonstrated that the excellent photocatalytic activity of T1-2Cu benefited from the appropriate amount of Cu 2+ 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 2+ 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 2+ ions also provided more accessible active sites and more probabilities for the adsorption and activation of CO 2 reactants.