Synergy of Electron Transfer and Electron Utilization via Metal–Organic Frameworks as an Electron Buffer Tank for Nicotinamide Regeneration

Abstract

Solar energy conversion by photocatalysis holds promise in energy supply, but its efficiency is hindered by the mismatch in charge generation, transfer, and utilization. In natural photosynthesis, photosystem I (PSI) exhibits an intrinsic quantum efficiency of nearly 100% in solar energy conversion. The elaborate synergy of electron transfer and electron utilization guarantees the conversion of unstable excited electrons to stable electrons in reduced nicotinamide adenine dinucleotide phosphate (NADPH). To demonstrate this in vitro, we report a design of core−shell metal−organic frameworks (MOFs) as an "electron buffer tank" to coordinate electron transfer and electron utilization in photocatalysis. The electrons are generated via the irradiation on photosensitizers (2-aminoterephthalic acid, NH 2 -BDC) in the core and then transferred to Zr 6 O 8 clusters on the shell through the light-induced ligand-to-metal charge transfer mechanism. Neighboring reaction centers, [Cp*Rh(bpydc)H 2 O] 2+ , on the MOFs behave as the electron buffer tank and store these electrons in the form of hydrides for subsequent regeneration of reduced nicotinamide adenine dinucleotide (NADH). The electron lifetime is prolonged from nanoseconds to seconds, leading to 2.27-fold enhancement of electron availability and 2.08-fold enhancement of activity compared to the homogeneous reaction counterpart. The coupling of NADH regeneration and enzyme catalysis further enables the asymmetric reduction of carbonyl to chiral amine. The electron buffer tank concept may offer a generic strategy to coordinate mass transfer and chemical reaction in a broad range of catalytic processes.

Investigation of Water‐Stable Perovskite DMASnIxBr3−x for Photoenzyme Catalysis in Aqueous Solution

“…But, this mediator-free behavior is pH-dependent with a yield much higher at pH % 9 than that at pH % 7.4 ( Figure S13, Supporting Information), which is consistent with the previous reports. [4,6] The alkaline environment can serve to neutralize and remove the H þ released in the regeneration step, shifting the reaction in favor of NADH formation. [4] More fascinatingly, the NADH could be regenerated with a yield about 37% even without the sacrificial agent of triethanolamine (TEOA), as shown in Figure S14, Supporting Information.…”

“…[4,6] The alkaline environment can serve to neutralize and remove the H þ released in the regeneration step, shifting the reaction in favor of NADH formation. [4] More fascinatingly, the NADH could be regenerated with a yield about 37% even without the sacrificial agent of triethanolamine (TEOA), as shown in Figure S14, Supporting Information. As we know, the use of TEOA as an electron donor may cause the accumulation of the oxidized form of TEOA þ in the photochemical reaction system.…”

“…However, the high cost of NADH and the stoichiometric consumption of NADH in the oxidoreductase catalysis entail the economic, environment‐friendly methods for NADH regeneration. [ 4–6 ] Continuing efforts have been devoted to in situ NADH regeneration from oxidized counterpart by enzymatic, [ 1,6 ] chemical, [ 7 ] electrochemical, [ 8 ] and photochemical [ 9 ] routes. Light‐driven NADH regeneration by semiconductor photocatalysis is very promising, and a lot of photocatalysts, such as g‐C 3 N 4 , [ 6 ] metal–organic frameworks, [ 10,11 ] and covalent organic frameworks, [ 12,13 ] have been reported for fulfilling such purpose.…”

“…However, the high cost of NADH and the stoichiometric consumption of NADH in the oxidoreductase catalysis entail the economic, environment-friendly methods for NADH regeneration. [4][5][6] Continuing efforts have been devoted to in situ NADH regeneration from oxidized counterpart by enzymatic, [1,6] chemical, [7] electrochemical, [8] and photochemical [9] routes.…”

Fabrication of NanoCOF/Polyoxometallate Composites for Photocatalytic NADH Regeneration via Cascade Electron Relay

“…NAD(P)H is a cofactor in enzymatic reduction and the regeneration of NAD(P)H is essential for the practical application of reductive enzymes. [25][26][27][28][29][30][31][32][33][34] According to previous reports, HPB could be excited by visible light to form HPB* with reductive potential more negative than [Cp*Rh(bpy)H 2 O] 2þ , thus, it is possible for nTp-TTA/POM-x to drive the photocatalytic NAD þ reduction with cascade electron relay on the basis of energy diagram ( Figure 3A). [14] The photocatalytic NADH regeneration was used as a model reaction to test the catalytic performance of nTp-TTA/POM-x with [Cp*Rh(bpy)H 2 O] 2þ as electron mediator and TEOA as hole sacrificial reagent using Xe lamp (λ ≥ 420 nm) ( Table 1).…”