Modulating metal.organic framework structure by metal ion stimulation for photocatalytic CO₂ reduction reaction

A 2D Cd- based metal- organic framework with moderate coordination bond strength and adequate framework flexibility was obtained by self- assembly, namely {[Cd(HL)(BPY)(0.5)(H2O)]center dot (H2O)-H-2} n (1), where H3L=4,4',4.-(nitrilotris(methylene))tribenzoic acid, BPY=4,4'-bipyridine. Due to the unique structural features, under the stimulation of metal ions (Zn2+/Ni2+/Co2+), 1 gradually transforms into the MOF structures dominated by the corresponding metal ions (2, 3, and 4). During this process, with the exchanges of Cd2+.Zn2+, Cd2+.Ni2+, and Cd2+.Co2+, the free Cd2+ and L-3- in the channel of 1 fuse with the backbone, leading to the channel space expansion and secondary building unit ( SBU) transformation to form a tunable backbone. The photocatalytic CO2 reduction results show that the new structures obtained by ion exchange do not have a great improvement in catalytic efficiency, but have a great increase in product selectivity (3 demonstrated 100% CO selectivity). CCDC: 2299888, 1; 2299889, 2; 2299890, 3; 2299891, 4.