Chitosan confinement enhances hydrogen photogeneration from a mimic of the diiron subsite of [FeFe]-hydrogenase

Abstract

Nature has created [FeFe]-hydrogenase enzyme as a hydrogen-forming catalyst with a high turnover rate. However, it does not meet the demands of economically usable catalytic agents because of its limited stability and the cost of its production and purification. Synthetic chemistry has allowed the preparation of remarkably close mimics of [FeFe]-hydrogenase but so far failed to reproduce its catalytic activity. Most models of the active site represent mimics of the inorganic cofactor only, and the enzyme-like reaction that proceeds within restricted environments is less well understood. Here we report that chitosan, a natural polysaccharide, improves the efficiency and durability of a typical mimic of the diiron subsite of [FeFe]-hydrogenase for photocatalytic hydrogen evolution. The turnover number of the self-assembling system increases B4,000-fold compared with the same system in the absence of chitosan. Such significant improvements to the activity and stability of artificial [FeFe]-hydrogenase-like systems have, to our knowledge, not been reported to date.

Comprehensive review and future perspectives on the photocatalytic hydrogen production

“…The use of bio‐inspired [FeFe]‐hydrogenase mimics in HOMPHPs allows reaching very high H 2 production yields; Jian et al (2013) and Wang et al (2013) reported a turnover number (TON) of 52 000 and 27 000 mol H2 / mol cat. , respectively …”

“…The combination of molecular catalysts and quantum dots as photosensitizers, in a system with [FeFe]‐hydrogenase mimics as catalyst, ascorbic acid as electron donor, methanol–H 2 O mixture as solvent and CdTe quantum dots as photosensitizer, has led to TON higher than 50 000 mol H2 /mol cat. Jian et al (2016) compared the performance of CdSe quantum dots and [Ru (bpy) 3 ] 2+ as photosensitizer using [FeFe]‐hydrogenase mimics as catalyst, ascorbic acid as electron donor and H 2 O as solvent. TON of >25 000 mol H2 /mol cat.…”

Biomimetic Complexes for Production of Dihydrogen and Reduction of CO2

“…In related work, Wu and coworkers demonstrated that confinement of the catalyst in a chitosan network, a naturally occurring polysaccharide, results in significant stabilization. They employed a CdTe quantum dot as photosensitizer, and the system is stable for 40 h with a turnover number of up to 52,000, a factor of 4,000 higher than the same components simply free in solution [139]. Unfortunately, the TOF is very low with an initial value of 1 s À1 .…”

Artificial hydrogenase: biomimetic approaches controlling active molecular catalysts

“…This short review summarizes recent advances in development of an artificial H 2 ase on the basis of a peptide or protein framework. Hybrid H 2 ases in other combinations, such as dendrimers, sugars and nanomaterials will not be [22][23][24][25][26] discussed.…”