TiO₂@CoAl-layered double hydroxide (LDH) core–shell nanospheres are fabricated via hydrothermal synthesis of TiO₂ hollow nanospheres followed by in situ growth of CoAl-LDH shell, which exhibit an extraordinarily high photocatalytic activity toward oxygen evolution from water oxidation. The O₂ generation rates of 2.34 and 2.24 mmol h⁻¹ g⁻¹ are achieved under full sunlight (>200 nm) and visible light (>420 nm), respectively, which are among the highest photocatalytic activities for oxygen production to date. The reason is attributed to the desirable incorporation of visible- light-active LDH shell with UV light-responsive TiO₂ core for promoted solar energy utilization. Most importantly, the combined experimental results and computational simulations reveal that the strong donor–acceptor coupling and suitable band matching between TiO₂ core and LDH shell facilitate the separation of photoinduced electron-hole pairs, accounting for the highly efficient photocatalytic performance. Therefore, this work provides a facile and cost-effective strategy for the design and fabrication of hierarchical semiconductor materials, which can be applied as photocatalyst toward water splitting and solar energy conversion.

Transparent and flexible gas-barrier materials have shown broad applications in electronics, food, and pharmaceutical preservation. Herein, we report ultrahigh-gas-barrier films with a brick–mortar–sand structure fabricated by layer-by-layer (LBL) assembly of XAl-layered double hydroxide (LDH, X=Mg, Ni, Zn, Co) nanoplatelets and polyacrylic acid (PAA) followed by CO₂ infilling, denoted as (XAl-LDH/PAA)_n-CO₂. The near-perfectly parallel orientation of the LDH “brick” creates a long diffusion length to hinder the transmission of gas molecules in the PAA “mortar”. Most significantly, both the experimental studies and theoretical simulations reveal that the chemically adsorbed CO₂ acts like “sand” to fill the free volume at the organic–inorganic interface, which further depresses the diffusion of permeating gas. The strategy presented here provides a new insight into the perception of barrier mechanism, and the (XAl-LDH/PAA)_n-CO₂ film is among the best gas barrier films ever reported.

Transparent and flexible gas-barrier materials have shown broad applications in electronics, food, and pharmaceutical preservation. Herein, we report ultrahigh-gas-barrier films with a brick–mortar–sand structure fabricated by layer-by-layer (LBL) assembly of XAl-layered double hydroxide (LDH, X=Mg, Ni, Zn, Co) nanoplatelets and polyacrylic acid (PAA) followed by CO₂ infilling, denoted as (XAl-LDH/PAA)_n-CO₂. The near-perfectly parallel orientation of the LDH “brick” creates a long diffusion length to hinder the transmission of gas molecules in the PAA “mortar”. Most significantly, both the experimental studies and theoretical simulations reveal that the chemically adsorbed CO₂ acts like “sand” to fill the free volume at the organic–inorganic interface, which further depresses the diffusion of permeating gas. The strategy presented here provides a new insight into the perception of barrier mechanism, and the (XAl-LDH/PAA)_n-CO₂ film is among the best gas barrier films ever reported.