Bromine Vapor Induced Continuous p- to n-Type Conversion of a Semiconductive Metal-Organic Framework Cu[Cu(pdt) 2 ].

Guest-promoted modulation of the electronic states in metal-organic frameworks (MOFs) has brought about a new field of interdisciplinary research, including host-guest chemistry and solid-state physics. Although there are dozens of studies on guest-promoted enhancement of the electrical conductivity properties, including stoichiometry, conductive carriers and structure-property relationships have been scarcely studied in detail. Herein, we studied the effects of continuous and controlled bromine vapor doping on structural, optical, thermoelectric, and semiconducting properties of Cu[Cu(pdt) ₂ ] (pdt = 2,3-pyrazinedithiolate) as a function of bromine stoichiometry. We demonstrated that the same material could act as both p- and n-type semiconductors by tuning the stoichiometry of Br doped in Br _x @Cu[Cu(pdt) ₂ ], and a change in the charge-carrier type from holes in pristine MOF to electrons upon bromine vapor doping was observed. Bromine molecules acted as an oxidant, causing the selective oxidation of [Cu ^II (pdt) ₂ ] in the host framework. In addition, a redox hopping pathway between the partially oxidized Cu ^II /Cu ^III center contributed to the enhancement of the electrical conductivity of the MOF.