Pore Size Control via Multiple-Site Alkylation to Homogenize Sub-Nanoporous Covalent Organic Frameworks for Efficient Sieving of Xenon/Krypton

Branched-Chain-Induced Host-Guest Assembly in Covalent-Organic Frameworks for Efficient Separation of No-Carrier-Added 177Lu

No-carrier-added (NCA) 177Lu is one of the most interesting nuclides for endoradiotherapy. With the dramatically rapid development of radiopharmaceutical and nuclear medicine, there is a sharp increase in the radionuclide supply of NCA 177Lu, which has formed a great challenge to current radiochemical separation constituted on classical materials. Hence, it is of vital importance to design and prepare new functional materials able of recovering 177Lu from an irradiated target with excellent efficacy. In this work, we proposed to apply noncovalent interactions to regulate the porous properties of covalent organic frameworks (COFs) by tuning the branched chain, rendering related covalent hosts different encapsulation abilities toward a flexible guest, 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (P507). More interestingly, we found that the noncovalent interaction has a great effect on the host-guest complexes, which can achieve efficient NCA 177Lu separation with high recovery (95.97%). A systematic mechanism combined with experimental and theoretical investigations has confirmed that the noncovalent interactions between COFs and P507 play a preeminent role in adjusting the macroscopic properties of the host-guest complexes. This work not only uncovers that noncovalent interactions can affect the basic properties of covalent organic bonded materials but also provides a strategy for the design and preparation of other new moieties with specific functionalities.

A facile and scalable synthetic method for covalent organic nanosheets: ultrasonic polycondensation and photocatalytic degradation of organic pollutants

Covalent organic framework nanosheets (COF NSs or CONs), as compared to their bulk counterparts two-dimensional (2D) covalent organic frameworks (COFs), exhibit superior performance in many aspects due to their fully accessible active sites benefiting from their ultrathin porous 2D structures. The development of a scalable synthetic methodology for CONs is crucial to further exploration of their unique properties and practical applications. Herein, we report an efficient strategy to fabricate ultrathin CONs through direct polycondensation of monomers under ultrasonic treatment and mild conditions. This method is facile and scalable, which is demonstrated by gram-scale synthesis of two ultrathin 2D CONs in several hours. Moreover, the as-prepared ultrathin CONs show excellent heterogeneous photocatalytic performance for the degradation of organic pollutants (dyes as representatives), remarkably superior to the bulk COFs prepared from the corresponding monomers under solvothermal conditions. This research provides a new roadmap for the scalable and facile synthesis of ultrathin CONs, which is of paramount importance for fully exploring the tremendous potential of this emerging type of 2D material.

We develop a strategy to efficiently fabricate ultrathin covalent organic framework nanosheets (CONs) through direct polycondensation of monomers under ultrasonic treatment. The CONs exhibit excellent photocatalytic performance for the degradation of organic pollutants.