Photosensitizer‐Anchored 2D MOF Nanosheets as Highly Stable and Accessible Catalysts toward Artemisinin Production

Abstract

2D metal–organic frameworks (2D‐MOFs) have recently emerged as promising materials for gas separations, sensing, conduction, and catalysis. However, the stability of these 2D‐MOF catalysts and the tunability over catalytic environments are limited. Herein, it is demonstrated that 2D‐MOFs can act as stable and highly accessible catalyst supports by introducing more firmly anchored photosensitizers as bridging ligands. An ultrathin MOF nanosheet‐based material, Zr‐BTB (BTB = 1,3,5‐tris(4‐carboxyphenyl)benzene), is initially constructed by connecting Zr 6 ‐clusters with the tritopic carboxylate linker. Surface modification of the Zr‐BTB structure was realized through the attachment of porphyrin‐based carboxylate ligands on the coordinatively unsaturated Zr metal sites in the MOF through strong Zr‐carboxylate bond formation. The functionalized MOF nanosheet, namely PCN‐134‐2D, acts as an efficient photocatalyst for 1 O 2 generation and artemisinin production. Compared to the 3D analogue (PCN‐134‐3D), PCN‐134‐2D allows for fast reaction kinetics due to the enhanced accessibility of the catalytic sites within the structure and facile substrate diffusion. Additionally, PCN‐134(Ni)‐2D exhibits an exceptional yield of artemisinin, surpassing all reported homo‐ or heterogeneous photocatalysts for the artemisinin production.

General Approach to Metal-Organic Framework Nanosheets With Controllable Thickness by Using Metal Hydroxides as Precursors

“…As known, MOFs are widely used in heterogeneous catalysis because of their high surface area, porosity, and chemical tunability. More importantly, like other 2D materials, the MOF nanosheets possess many highly accessible active sites on their surface, which can act as diffusion-free heterogeneous catalysts and should be significant for the catalytic applications Huang et al, 2017;Wang Y. et al, 2019;Xiao et al, 2019). As a proof-of-concept application, the molecular oxygen epoxidation of olefins, which is a highly important oxidation reaction in industrial processes (Punniyamurthy et al, 2005), was chosen as a probe reaction.…”

Highly Stable Phosphonate‐Based MOFs with Engineered Bandgaps for Efficient Photocatalytic Hydrogen Production

“…Metal–organic frameworks (MOFs) feature unique structures that consist of metal clusters or ions connected by organic linkers (e.g., organophosphonic acids, carboxylic acids), showing a high level of structural and functional tunability. [ 5,6 ] The metallic blocks mainly correspond to di/trivalent cations of 3d transition metals (e.g., Fe, Zn, Ni) and 3p metals, [ 5–9 ] among which Ti is an attractive candidate because of its relatively low cost, redox activity, and photocatalytic properties. [ 10–16 ] Incorporating Ti‐oxo clusters delivers the semiconductor behavior of the MOFs with decent solar energy conversion efficiency, due to the facilitated electron transfer from the photoexcited organic linkers to the Ti‐oxo clusters (i.e., linker‐to‐cluster charge transfer, termed as LCCT).…”

Thin‐Layered Photocatalysts

“…It is worth mentioning that the modified materials (PCN‐134‐Ni) display high performance for photocatalytic producing artemisinin. [ 68 ] Another fascinating example is reported by Qiao's group, in which a thin‐layered Ni‐based MOF (NMF) [Ni(phen)(oba)] n ·0.5 n H 2 O has been prepared. Due to its high surface area and suitable pore size, the CdS nanoparticles can be decorated on Ni‐MOLs surface, thus generating an efficient photocatalytic system.…”

“…Because the monocarboxylic acids can change the distance of interlayers, and the water can partially replace the terminal carboxylate ligands, thus reducing the thickness of the MOLs materials. [ 68 ] Above all, hydro/solvothermal methods have several advantages for fabricating thin‐layered materials, such as easy operating, high yield, and low cost. However, the growth mechanism of the materials is hard to conclude.…”