Many enzymes use adaptive frameworks to preorganize substrates,
accommodate various structural and electronic demands of intermediates,
and accelerate related catalysis. Inspired by biological systems,
a Ru-based molecular water oxidation catalyst containing a configurationally
labile ligand [2,2′:6′,2″-terpyridine]-6,6″-disulfonate
was designed to mimic enzymatic framework, in which the sulfonate
coordination is highly flexible and functions as both an electron
donor to stabilize high-valent Ru and a proton acceptor to accelerate
water dissociation, thus boosting the catalytic water oxidation performance
thermodynamically and kinetically. The combination of single-crystal
X-ray analysis, various temperature NMR, electrochemical techniques,
and DFT calculations was utilized to investigate the fundamental role
of the self-adaptive ligand, demonstrating that the on-demand configurational
changes give rise to fast catalytic kinetics with a turnover frequency
(TOF) over 2000 s–1, which is compared to oxygen-evolving
complex (OEC) in natural photosynthesis.