Tuning the Optoelectronic Properties of Hybrid Functionalized MIL-125-NH₂ for Photocatalytic Hydrogen Evolution

Abstract

Metal–organic frameworks (MOFs) constructed with mixed ligands have shown great promise in the generation of materials with improved sorption, optical, and electronic properties. With an experimental, spectroscopic, and computational approach, herein, we investigated how the incorporation of different functionalized ligands within the structure of MIL-125-NH2 affects its performance in photocatalytic water reduction. We found that multiligand incorporation within the MOF structure has an impact on the light absorption spectrum and the electronic structure. These combined modifications improve the photocatalytic performance of MIL-125-NH2, thereby increasing the rate of hydrogen evolution reaction. Of the four nanoparticle/MOF photocatalytic systems tested, we showed that the Pt/MIL-125-NH2/(OH)2 system (Pt nanoparticle plus MIL-125-NH2 with amino and dihydroxyl functionalized ligands) outperforms its counterpart Pt/MIL-125-NH2 system, attributed to the enhanced p−π conjugation between the lone pairs of O atoms and their aromatic ligands resulting in a red-shifted absorption spectrum and greater spatial distribution of electron density.

Designing Dual-Functional Metal–Organic Frameworks for Photocatalysis

“…Metal–organic frameworks (MOFs) with versatile structures and tunable physicochemical properties present an ideal platform for such a task. As photocatalytic materials, MOFs are theoretically superior to traditional semiconductors due to their: (i) high porosity, which allows co-catalysts and organic molecules to diffuse within them, increasing their interactions, and (ii) highly tunable structures that allow their optoelectronic properties, conductivity, and hydrolytic stability to be modified by changing the metal ions or functionalizing the organic ligand. − Moreover, traditional semiconductors are limited by their ability to primarily absorb UV light, whereas MOFs can be tuned to absorb visible light that represents a more significant fraction of solar energy reaching Earth. Hence, photocatalysts with a broader light absorption range can be useful in DFP. , …”

“…Hence, photocatalysts with a broader light absorption range can be useful in DFP. 26,31 MOFs have been previously applied in DFP, such as MIL-125-NH 2 , which photodegraded rhodamine B while producing H 2 at a rate of 335 μmol h −1 g −1 . 24 PCN-777 simultaneously generated H 2 (30 μmol h −1 g −1 ) and oxidized benzylamine with 90% selectivity.…”

Construction of MIL-125-NH2@BiVO4 Composites for Efficient Photocatalytic Dye Degradation

“…Besides, metal–organic frameworks (MOFs), composed of metal units and organic ligands with large pore sizes, high surface areas, structure adaptability, and flexibility, are attractive porous crystal materials and have been found to have a huge potential in the photocatalytic field. , Prior studies demonstrated that MOFs possess a semiconductor-like property and can be directly used as photocatalysts. Taking MIL-125-NH 2 as an example, , it could be stimulated by ultraviolet light with a small band gap energy at about 2.6 eV in which metal clusters serve as the conduction band (CB) and organic linkers play the role of the valence band (VB). Unfortunately, MIL-125-NH 2 suffers from weak visible light response and low efficiency.…”

“… 27 , 28 Prior studies demonstrated that MOFs possess a semiconductor-like property and can be directly used as photocatalysts. Taking MIL-125-NH 2 as an example, 29 , 30 it could be stimulated by ultraviolet light with a small band gap energy at about 2.6 eV in which metal clusters serve as the conduction band (CB) and organic linkers play the role of the valence band (VB). Unfortunately, MIL-125-NH 2 suffers from weak visible light response and low efficiency.…”

Strategies for Optimizing the Photocatalytic Water‐Splitting Performance of Metal–Organic Framework‐Based Materials

“…Very recently, the photocatalytic hydrogen production performance of amino (−NH 2 ) and/or hydroxyl (−OH) MIL‐125 was also investigated by Stylianou and coworkers. [ 73 ] Three different functionalized ligands (NH 2 ) 2 ‐BDC, OH‐BDC, and (OH) 2 ‐BDC, were embedded into the framework of MIL‐125 to form a π ‐conjugated structure consisting of weakly coupled single‐chromophore functionalized units.…”