Rational Design of Coordination Bond Connected Metal Organic Frameworks/MXene Hybrids for Efficient Solar Water Splitting

Metal organic frameworks (MOFs) have attracted great interest in photocatalysis, but their activity is hampered by the issue of severe carrier recombination. Here, through a carboxyl group assisted coordination route, MXene decorated with carboxyl groups provides chelation sites enabling coordination with UiO-66-NH2(Zr/Ti) (UZT) to fabricate a tightly connected UiO-66-NH2(Zr/Ti)/carboxyl-functionalized MXene (UZT/CFMX) heterostructure. This is the first instance of direct chemical bonding of MOFs-involved heterostructure via a coordination bond. The critical role of decorated carboxyl groups can be determined so that 1) these can help to establish a strong coordination bond between two materials; 2) act as bridge to promote the electrons transfer from MOFs to MXene, thus relieving carrier recombination, and 3) most interestingly, the carbon atom on the carboxyl group forms a bond with the oxygen from water stimulating the water to dissociate into OH* and H*, thus adding additional reaction pathways for promoting photocatalytic water splitting. Accordingly, the resulting UZT/CFMX shows efficient solar-driven photocatalytic performance for water splitting. The H-2 evolution rate is as high as 2187 mu mol g(-1) h(-1), 20 times higher than that of UZT and 4 times higher than that of UiO-66-NH2 (Zr/Ti)/MXene (UZT/MX), also surpassing the majority of reported MOF-based photocatalysts.

Automated summary

Metal organic frameworks (MOFs) are widely used as photocatalysts, but carrier recombination limits their activity. In this study, carboxyl groups on MXene were used to coordinate with UiO-66-NH2(Zr/Ti) (UZT) and create a tightly connected UiO-66-NH2(Zr/Ti)/carboxyl-functionalized MXene (UZT/CFMX) heterostructure. This unique heterostructure showed efficient solar-driven photocatalytic performance for water splitting, with a hydrogen evolution rate much higher than other MOF-based photocatalysts.