Competitive coordination initiated one-pot synthesis of core–shell Bi-MOF@BiOX (X = I, Br and Cl) heterostructures for photocatalytic elimination of mixed pollutants.

[Display omitted] • Core-shell Bi-MOF@BiOX is fabricated by a one-pot solvothermal strategy. • The competitive coordination effect to Bi3+ makes BiOX and Bi-MOF contact closely. • Bi-MOF@BiOX has nice activities on Cr(VI), tetracycline and o-nitrophenol removal. • For above reactions, more than 13, 7, 5-time enhancements of activity are achieved. • Enhanced activities are observed for the treatment of mixed pollutants. Core-shell Bi-MOF@BiOX (X = I, Br and Cl) hybrids were fabricated by a one-pot solvothermal strategy via regulating the concentration and type of halogen ions in the Bi-based CAU-17 synthesis. By virtue of the competitive coordination effect to Bi3+ between CAU-17 and BiOX, CAU-17 was converted into another Bi-MOF with similar structures and compositions. Moreover, Bi3+ plays the role of "bridge" and endows an intimate interface contact between BiOX and the Bi-MOF, which immensely expedites the charge and mass transportation. The obtained Bi-MOF@BiOX hierarchical heterostructures were applied to photocatalytic elimination of solo and mixed pollutants (Cr(VI)/tetracycline and Cr(VI)/o-nitrophenol), and exhibited favorable performances. Choosing Bi-MOF@BiOI as a typical example, the corresponding performances for Cr(VI) reduction, tetracycline and o-nitrophenol degradation in their solo systems are 14, 10, 8 times higher than those of CAU-17, and 13, 7, 5 times higher than those of BiOI under visible light, respectively. Of note, the above photocatalytic performances could be further improved in the coexisting environment of Cr(VI) and tetracycline or o-nitrophenol, which is attributed to the elevated charge separation efficiency caused by the timely consumption of photo-excited electrons and holes. This work gives some insights into the delicate design of MOF photocatalysts and their applications in environmental restoration. [ABSTRACT FROM AUTHOR]