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

Abstract

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-NH 2 (Zr/Ti) (UZT) to fabricate a tightly connected UiO-66-NH 2 (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 µmol g −1 h −1 , 20 times higher than that of UZT and 4 times higher than that of UiO-66-NH 2 (Zr/Ti)/MXene (UZT/MX), also surpassing the majority of reported MOF-based photocatalysts.

Electronic Modulation of Metal–Organic Frameworks by Interfacial Bridging for Efficient pH‐Universal Hydrogen Evolution

“…In addition, the interfacial bridges formed by MXene and metal sites can tune the Fermi level of the active center, resulting in enhanced intrinsic activity compared to conventional catalyst substrates. [32,34,45] Despite so many advantages, the influence of the interfacial microstructure-activity relationship between MXene and MOFs for the HER catalytic process is so far rarely reported. Therefore, the reciprocal decoration between multifunctional MXene and 2D MOFs is expected to be an efficient pH-universal electrocatalyst for hydrogen evolution.…”

“…[31] Moreover, chemical bond bridges in the interface can trigger fast electron transfer, which can optimize the HER free energy and lead to accelerated reaction kinetics. [32,33] It has been widely investigated in many electrocatalytic processes for realizing new functions that are difficult to achieve by any individual material. [34,35] However, the modulation of active sites based on interfacial bond bridging formed by traditional metal oxide and hydroxide substrates is unsatisfactory to maintain durability in extreme catalytic environments.…”

MXene-Based Nanomaterials for Multifunctional Applications

“…Mxene hybrid and composites exhibit significantly enhanced catalytic activities and stability compared to pristine MXene due to synergistic coupling between MXenes and their secondary materials. Currently, numerous organic and inorganic materials such as TM carbides, TM phosphides [ 60 ], TM chalcogenides, TM oxides [ 61 ], layered double hydroxides, metal-organic frameworks [ 62 , 63 , 64 ], graphitic carbon nitride [ 65 ], carbon nanotubes [ 66 ], quantum dots, metallic alloys, polymers, etc. have been combined with MXenes to form MXene hybrids/composites [ 55 , 61 , 67 ].…”

Pristine Metal–Organic Frameworks and their Composites for Renewable Hydrogen Energy Applications

“…The resulting composite (UZT/CFMX) exhibited the highest H 2 production rates (2187 µmol g −1 h −1 ), which is 20 and 4 times higher than bare MOF and UZT/MX composite, respectively (Figure 8c,d). [209] Benefitted from the advantages of liposome membranes (faster charge separation and provided hydrophobic side for improvement of the water stability), Wang et al developed a composite for overall water splitting reaction. They have anchored HERMOF and WORMOF nanosheets on liposome vehicles (comprising of lecithin (PC) and cholesterol (Chol) in a molar ratio of 3:1) for the improvement of charge carrier separation via separating the oxidative and reductive components in hydrophobic and hydrophilic regions of the lipid bilayer respectively.…”

“…d) Comparison of photocurrent responses of UZT/CFMX series. Reproduced with permission [209]. Copyright 2022, Wiley-VCH GmbH.…”