4 research outputs found
A Water-Stable Boronate Ester Cage
The reversible condensation
of catechols and boronic
acids to boronate
esters is a paradigm reaction in dynamic covalent chemistry. However,
facile backward hydrolysis is detrimental for stability and has so
far prevented applications for boronate-based materials. Here, we
introduce cubic boronate ester cages 6 derived from hexahydroxy
tribenzotriquinacenes and phenylene diboronic acids with ortho-t-butyl substituents. Due to steric shielding,
dynamic exchange at the Lewis acidic boron sites is feasible only
under acid or base catalysis but fully prevented at neutral conditions.
For the first time, boronate ester cages 6 tolerate substantial
amounts of water or alcohols both in solution and solid state. The
unprecedented applicability of these materials under ambient and aqueous
conditions is showcased by efficient encapsulation and on-demand release
of Ī²-carotene dyes and heterogeneous water oxidation catalysis
after the encapsulation of ruthenium catalysts
A Water-Stable Boronate Ester Cage
The reversible condensation
of catechols and boronic
acids to boronate
esters is a paradigm reaction in dynamic covalent chemistry. However,
facile backward hydrolysis is detrimental for stability and has so
far prevented applications for boronate-based materials. Here, we
introduce cubic boronate ester cages 6 derived from hexahydroxy
tribenzotriquinacenes and phenylene diboronic acids with ortho-t-butyl substituents. Due to steric shielding,
dynamic exchange at the Lewis acidic boron sites is feasible only
under acid or base catalysis but fully prevented at neutral conditions.
For the first time, boronate ester cages 6 tolerate substantial
amounts of water or alcohols both in solution and solid state. The
unprecedented applicability of these materials under ambient and aqueous
conditions is showcased by efficient encapsulation and on-demand release
of Ī²-carotene dyes and heterogeneous water oxidation catalysis
after the encapsulation of ruthenium catalysts
A Water-Stable Boronate Ester Cage
The reversible condensation
of catechols and boronic
acids to boronate
esters is a paradigm reaction in dynamic covalent chemistry. However,
facile backward hydrolysis is detrimental for stability and has so
far prevented applications for boronate-based materials. Here, we
introduce cubic boronate ester cages 6 derived from hexahydroxy
tribenzotriquinacenes and phenylene diboronic acids with ortho-t-butyl substituents. Due to steric shielding,
dynamic exchange at the Lewis acidic boron sites is feasible only
under acid or base catalysis but fully prevented at neutral conditions.
For the first time, boronate ester cages 6 tolerate substantial
amounts of water or alcohols both in solution and solid state. The
unprecedented applicability of these materials under ambient and aqueous
conditions is showcased by efficient encapsulation and on-demand release
of Ī²-carotene dyes and heterogeneous water oxidation catalysis
after the encapsulation of ruthenium catalysts
A Covalent Organic Framework for Cooperative Water Oxidation
The future of water-derived hydrogen as the āsustainable
energy sourceā straightaway bets on the success of the sluggish
oxygen-generating half-reaction. The endeavor to emulate the natural
photosystem II for efficient water oxidation has been extended across
the spectrum of organic and inorganic combinations. However, the achievement
has so far been restricted to homogeneous catalysts rather than their
pristine heterogeneous forms. The poor structural understanding and
control over the mechanistic pathway often impede the overall development.
Herein, we have synthesized a highly crystalline covalent organic
framework (COF) for chemical and photochemical water oxidation. The
interpenetrated structure assures the catalyst stability, as the catalystās
performance remains unaltered after several cycles. This COF exhibits
the highest ever accomplished catalytic activity for such an organometallic
crystalline solid-state material where the rate of oxygen evolution
is as high as ā¼26,000 Ī¼mol Lā1 sā1 (second-order rate constant k ā
1650 Ī¼mol L sā1 gā2). The
catalyst also proves its exceptional activity (k ā
1600 Ī¼mol L sā1 gā2) during
light-driven water oxidation under very dilute conditions. The cooperative
interaction between metal centers in the crystalline network offers
20ā30-fold superior activity during chemical as well as photocatalytic
water oxidation as compared to its amorphous polymeric counterpart