Mixed-Component Metal–Organic Framework for Boosting Synergistic Photoactivation of C(sp³)–H and Oxygen

Abstract

Synergistic catalysis is an efficient and powerful strategy for simultaneously activating reactants by multiple active sites to promote the efficiency of difficult and challenging catalytic reactions. Meanwhile, enzymes with multi-active-site synergistic catalytic properties possessing high efficiency and high selectivity have become the goal pursued in the field of catalytic chemistry in recent years. Metal–organic frameworks (MOFs), as an effective heterogeneous catalytic platform, that can integrate multiple active sites for synergistic catalysis like enzymatic systems have recently attracted interest. Herein, we report a doubly interpenetrated metal–organic framework with dual active sites, MnIII–porphyrin sites to directly activate molecular oxygen and fluoren-9-one sites to produce a hydrogen atom transfer (HAT) agent by the proton-coupled electron transfer (PCET) process to simultaneously activate inert C(sp3)–H bonds for efficient inert C(sp3)–H bond oxidation under mild conditions. The bifunctional mixed-component MOF structure forced the two catalytic sites closer together to a more suitable distance, exhibiting high photocatalytic activity for inert C(sp3)–H bond oxidation with almost unique selectivity under mild conditions. The density functional theory (DFT) calculation of free energy during the whole catalytic process demonstrated that it is likely that the synergistic catalytic process occurred in the interframework to accelerate the catalytic reaction. The assembling mixed-component MOF for synergistic catalysis would be a prospective approach for the inert C(sp3)–H photoactivation and functionalization.

Heterogeneous Photocatalytic Strategies for C(sp3)−H Activation

“…[98] In the past decade, metal-organic frameworks (MOFs), a class of crystalline porous materials with well-defined and tailorable structures, [99][100] have become one of the most promising heterogeneous photocatalysts for C(sp 3 )À H activation. [74,[101][102][103][104][105][106] However, the issue regarding MOFs as semiconductors or molecules assembled in a periodic manner remains highly controversial, [107][108] both semiconductor [109] and charge transfer process [110] have been proposed.…”

“…Introducing reactive radical species generated from HAT reagents for C(sp 3 )À H activation has been widely investigated. [89,103,106,[123][124][128][129] For example, Zhao et al combined NHPI and a MOF photocatalyst to generate reactive radical species (PINO) in situ for C(sp 3 )À H activation of ethers and aromatic hydrocarbons. [106] König et al developed a strategy for producing halogen radicals ( * Br or * Cl) during the reaction via energy-transfer process between mpg-CN and a nickel catalyst for C(sp 3 )À H activation of amides.…”

Visible-light-driven organic oxidation over CdS-doped metal–organic frameworks

“…The highest photocurrent response and the smallest radius in the Nyquist plots were observed for CdS-3@DUT-52, which indicates that CdS-3@DUT-52 possesses the highest charge-separation efficiency. 51 The photoluminescence (PL) spectra of CdS and CdS-3@DUT-52 showed a peak at 443 nm corresponding to the radiative recombination of photogenerated electrons and holes (Fig. S5 †).…”

Anderson-type polyoxometalate-based metal–organic framework as an efficient heterogeneous catalyst for selective oxidation of benzylic C–H bonds

“…For example, employing metal–organic frameworks (MOFs) as porous platform to accommodate NHPI, a variety of oxidative transformations were catalyzed by MOF/NHPI systems, including oxidative coupling of benzylamines, aerobic oxidation of alkanes and alkenes, and selective oxidation of benzylic C–H bonds. 28–32 In all these cases, the integrated catalyst systems showed catalytic performance superior to the homogeneous mixture of metal salts and NHPI.…”