Formation of willow leaf-like structures composed of NH2-MIL68(In) on a multifunctional multiwalled carbon nanotube backbone for enhanced photocatalytic reduction of Cr(VI)

Efficient separation and transfer of photogenerated electron/hole as well as enhanced visible light absorption play essential roles in photocatalytic reactions. To promote the photocatalytic reduction of Cr(VI), a toxic heavy metal ion, multiwalled carbon nanotube (MWCNT) was introduced as an electron acceptor into NH2-MIL-68(In). This led to the growth of a willow leaf-like metal-organic framework (MOF) on an MWCNT backbone forming MWCNT/NH2-MIL-68(In) (PL-1), which showed a highly efficient transfer of photogenerated carriers. Moreover, MWCNT incorporation introduced more mesopores for Cr(VI) diffusion and enhanced the visible light adsorption without lowering the conduction band position. As a result, the photocatalytic kinetic constant of PL-1 was found to be almost three times higher than that of the parent NH2-MIL-68(In). Thus, growing MOFs on MWCNTs provides a facile and promising solution for effective remediation of environmental pollution by utilizing solar energy. This work provides the first example of using MWCNT/MOF composites for photocatalytic reactions.