Lingyun Cao

Surface Modification of Two-Dimensional Metal-Organic Layers Creates Biomimetic Catalytic Microenvironments for Selective Oxidation

Microenvironments in enzymes play crucial roles in controlling the activities and selectivities of reaction centers. Herein we report the tuning of the catalytic microenvironments of metal-organic layers (MOLs), a two-dimensional version of metal-organic frameworks (MOFs) with thickness down to a monolayer, to control product selectivities. By modifying the secondary building units (SBUs) of MOLs with monocarboxylic acids, such as gluconic acid, we changed the hydrophobicity/hydrophilicity around the active sites and fine-tuned the selectivity in photocatalytic oxidation of tetrahydrofuran (THF) to exclusively afford butyrolactone (BTL), likely a result of prolonging the residence time of reaction intermediates in the hydrophilic microenvironment of catalytic centers. Our work highlights new opportunities in using functional MOLs as highly tunable and selective two-dimensional catalytic materials.

Two‐Dimensional Metal‐Organic Layers as a Bright and Processable Phosphor for Fast White‐Light Communication

A metal-organic layer (MOL) is a new type of 2D material that is derived from metal-organic frameworks (MOFs) by reducing one dimension to a single layer or a few layers. Tetraphenylethylene-based tetracarboxylate ligands (TCBPE), with aggregation-induced emission properties, were assembled into the first luminescent MOL by linking with Zr6 O4 (OH)6 (H2 O)2 (HCO2 )6 clusters. The emissive MOL can replace the lanthanide phosphors in white light emitting diodes (WLEDs) with remarkable processability, color rendering, and brightness. Importantly, the MOL-WLED exhibited a physical switching speed three times that of commercial WLEDs, which is crucial for visible-light communication (VLC), an alternative wireless communication technology to Wi-Fi and Bluetooth, by using room lighting to carry transmitted signals. The short fluorescence lifetime (2.6 ns) together with high quantum yield (50 %) of the MOL affords fast switching of the assembled WLEDs for efficient information encoding and transmission.

A Dynamically Stabilized Single-Nickel Electrocatalyst for Selective Reduction of Oxygen to Hydrogen Peroxide

On-location electrochemical generation of H2 O2 is of great current interest. Herein, selective two-electron reduction of O2 to H2 O2 by a single [NiII (H2 O)6 ]2+ cation that is dynamically associated with a negatively charged metal-organic layer (MOL) by hydrogen bonding and coulombic interactions is reported. In contrast, NiII centers covalently immobilized on the MOL reduce O2 to H2 O in a four- electron process. Oxygen adsorption by [NiII (H2 O)6 ]2+ followed by two-electron reduction generates neutral [NiII (H2 O)4 (OH)(OOH)]0 , which momentarily disconnects from the negatively charged MOL to avoid the injection of additional electrons. Release of H2 O2 from [NiII (H2 O)4 (OH)(OOH)]0 regenerates [NiII (H2 O)6 ]2+ , which regains affinity to the MOL. Such dynamically associated NiII single-metal electrocatalysts ensure high selectivity and represent a new strategy for generating selective catalysts for electrochemical production of important chemicals.

Two-Dimensional Metal–Organic Layers on Carbon Nanotubes to Overcome Conductivity Constraint in Electrocatalysis

Application of metal-organic frameworks (MOFs) in electrocatalysis is of great interest, but is limited by low electrical conductivities of most MOFs. To overcome this limitation, we constructed a two-dimensional version of MOF-metal-organic layer (MOL) on conductive multiwalled carbon nanotubes (CNTs) via facile solvothermal synthesis. The redox-active MOLs supported on the CNT efficiently catalyze the electrochemical oxidation of alcohols to aldehydes and ketones. Interestingly, this CNT/MOL assembly also endowed the selectivity for primary versus secondary alcohols via well-designed interfacial interactions. This work opens doors toward a variety of designer electrocatalysts built from functional MOFs.