Multifunctional photoelectric sensors and catalysts for CO2RR and Cr(vi) solution based on a series of POM-based materials

Five new Keggin-based compounds, namely [CuI(dm4bt)2]4[GeW12O40] (1), [M4II(dm4bt)8(GeW12O40)2(H2O)2]·4H2O (M = Ni for 2 and Co for 3), [Co4II(dm4bt)8(SiW12O40)2(H2O)2]·6H2O (4) and [Cu2II(H2bdpm)(HBW12O40)(H2O)2]·H2O (5) (dm4bt = 2,2′-dimethyl-4,4′-bithiazole, H2bdpm = 1,1′-bis(3,5-dimethyl-1H-pyrazolate)methane), were synthesized through traditional hydrothermal methods. Compounds 1–5 can be used as photoelectric multifunctional sensors to detect various ions. As electrochemical sensors, n-CPEs have a good sensitivity and wide concentration range for nitrite. As fluorescent sensors, the title compounds have remarkable fluorescence detection performance for Cr2O72−. Furthermore, we modified the compounds as catalysts to investigate their catalytic activities for CO2 reduced to CO and the reduction of Cr(vi) to Cr(iii). The results show that these compounds have high catalytic activities.