Azobenzene-Functionalized UiO-66-NH2: Solid Base Catalysts with Photocontrollable Activity.

Heterogeneous solid base catalysts are highly expected due to their high activity and environmentally friendly nature in a variety of reactions. However, the catalytic activity of traditional solid base catalysts is controlled by external factors (such as temperature and pressure), and regulation of the activity by in situ changing their own properties has never been reported. Herein, we report a smart solid base catalyst by chemically anchoring the photoresponsive azobenzene derivative p-phenylazobenzoyl chloride (PAC) onto the metal-organic framework UiO-66-NH2 (UN) for the first time, which can regulate the catalytic activity through remote control of external light. The prepared catalysts have a regular crystal structure and photoresponsive properties. It is fascinating that the configuration of PAC can be isomerized easily during UV- and visible-light irradiation and resulted in regulation of the catalytic activity. In the Knoevenagel condensation of 1-naphthaldehyde and ethyl cyanoacetate to ethyl 2-cyano-3-(1-naphthalenyl)acrylate, the optimal catalyst shows up to 56.2% of change after trans/cis isomerization, while the change of the yield over UN is negligible. The regulated catalytic behavior can be assigned to the steric hindrance change of the catalysts under external light irradiation. This work may shed light on the design and construction of smart solid base catalysts with tailorable properties for various reactions.

Detachable Porous Organic Polymers Responsive to Light and Heat.

Stimuli-responsive porous materials have captured much attention due to the on-demand tunable properties. Most reported stimuli-responsive porous materials are based on molecule isomerism or host-guest interaction, and it is highly desired to develop new types based on different responsive mechanism. Herein, inspired by natural cells which have the ability to fuse and divide induced by external stimulation, we report a new type of stimuli-responsive porous material based on detachment mechanism. A detachable porous organic polymer, namely DT-POP-1, is fabricated from the polymerization of anthracene-containing monomer (AnMon) when irradiated by 365 nm UV light. DT-POP-1 can detach into the monomer AnMon when irradiated with 275 nm UV light or heat. Such polymerization/detachment is reversible. The detachment results in a big difference in porosity and adsorption capacity, making the present detachable porous polymer highly promising in adsorptive separation and drug delivery.