Visible light driven photocatalysts based on crystalline microporous metal halogenides received much less attention compared with dense or composite oxide semiconductors. Using the well-known photosensitive transition metal-complexes [TM(2,2-bipy) ] (TM=Fe, Co, Ni, Ru) as templates, a special three-dimensional (3D) metal halogenide framework of [TM(2,2-bipy) ]Cu Br was designed with [Cu Br ] cluster as 4-connected node. These microporous materials feature narrow band gaps and stable visible light driven photocatalytic properties including water reduction to provide H and photodegradation of organic pollutants. The study of electronic band structure shows that the TM complexes effectively prevent the recombination of photo-induced electron/hole pairs leading to excellent photocatalytic activity and photochemical stability. This work represents the first 3D microporous metal halogenides used as visible light driven photocatalyst to provide hydrogen energy.

With similar transition metal (TM) complex cations as structural directing agents (SDAs), six new hybrid lead bromides were synthesized and structurally characterized as [Co(2,2-bipy)]{[Co(2,2-bipy)]PbBr} (1), [Co(2,2-bipy)Br]PbBr (2), [TM(phen)]PbBr (TM = Co (3) and Ni (4)), [Co(2,2-bipy)]PbBr (5) and [Co(2,2-bipy)]PbBr·CHCN (6) with distinct structural types from zero-dimensional (0D) unit, one-dimensional (1D) chain to two-dimensional (2D) layer. Compound 1 contains the 0D {[Co(bipy)]PbBr} units built from the [PbBr] ring attached by three unsaturated [Co(2,2-bipy)] complexes via Co-Br bonds. Under the direction actions of different SDAs, compounds 2 and 3-4 contain two different types of [PbBr] chains based on the same octahedral [PbBr] units but with distinct connecting manners, respectively. Using the same [Co(2,2-bipy)] as SDA, compound 5 reveals a 1D [PbBr] double chain, whereas compound 6 features a 2D complex [PbBr] layer. The UV/vis diffuse-reflectance measurements reveal that the title compounds feature tunable band gaps of 1.70-2.29 eV. Under the visible light irradiation, sample 6 exhibits efficient and stable photocatalytic degradation activities over organic pollutants, which mainly originates from the multi-electronic effects of the TM complex cations. A possible photocatalytic mechanism is also proposed based on the radical trapping experiments and electronic band structural calculations.

By using transition-metal (TM) complex cationic dyes as structure-directing agents and photosensitizers, a series of inorganic-organic hybrid metal halides, namely, [TM(2,2'-bipy)]AgPbI [TM = Ni (1), Co (2) and Zn (3)], [Co(2,2'-bipy)]CuPbBr (4) and [TM(2,2'-bipy)]AgPbBr [TM = Ni (5) and Fe (6)], have been solvothermally prepared and structurally characterized. Compounds 1-3 feature 1D [AgPbI] chains built from the condensation of [AgI] dimers and [PbI] tetramers, and compounds 4, 5 and 6 contain similar 1D [CuPbBr] and [AgPbBr] chains, respectively. UV-Vis diffuse reflectance measurements reveal narrow band gaps of 1.75-2.18 eV for compounds 1-6, which lead to efficient and stable photocatalytic degradation activities over organic pollutants under visible light irradiation. Among the title compounds, sample 5 shows the highest photocatalytic degradation activity. The possible mechanism for their stable photocatalytic activities is proposed based on the experimental and theoretical studies.