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

Abstract

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.

A metal-organic framework constructed by ferrocene and titanium clusters for CO2 photoreduction under visible light

“…The LUMO level of Fe-Tc was higher than MOF-902, which should be attributed to the excellent electron-giving ability of ferrocene ligands. [12] .…”

“…As previously reported [12] , 74 mg of 4,4'-biphenyldicarboxaldehyde and 3 mL of methanol were added to a beaker and dissolved under ultrasound. Add 96 mg of p-aminobenzoic acid and 52 μL of isopropyl titanate to the reactor, followed by 3 ml of methanol and the aldehyde above the solution, stirring for 10 min.…”