Despite the excellent photodynamic and photothermal properties of organic molecular photosensitizers (PSs) and photothermal agents (PTAs), such as porphyrin and naphthalocyanine, their poor water solubility severely impedes their biological applications. Covalent organic frameworks (COFs), as an emerging class of organic crystalline porous materials, possess free active end groups (bonding defects) and large inner pores, which make them an ideal type of nanocarriers for loading hydrophobic organic molecular PSs and PTAs by both bonding defect functionalization (BDF) and guest encapsulation approaches to obtain multifunctional nanomedicines for PDT/PTT combination therapy. In this work, we report a nanoscale COF (NCOF) prepared via a facile synthetic approach under ambient conditions. Furthermore, a dual-modal PDT/PTT therapeutic nanoagent, VONc@COF-Por (3), is successfully fabricated by stepwise BDF and guest encapsulation processes. The covalently grafted porphyrinic PS (Por) and the noncovalently loaded naphthalocyanine PTA (VONc) are independently responsible for the PDT and PTT functionalities of the nanoagent. Upon visible (red LED) and NIR (808 nm laser) irradiation, VONc@COF-Por (3) displayed high 1O2 generation and photothermal conversion ability (55.9%), consequently providing an excellent combined PDT/PTT therapeutic effect on inhibiting MCF-7 tumor cell proliferation and metastasis, which was well evidenced by in vitro and in vivo experiments. We believe that the results obtained herein can significantly promote the development of NCOF-based multifunctional nanomedicines for biomedical applications.

Postsynthetic modification (PSM) has been demonstrated to be a powerful method for achieving new covalent organic frameworks (COFs) via single-step or multistep organic functional group transformations on established COF frameworks. PSM, however, might sometimes lead to collapse of the COF framework, decreases in crystallinity, or low postsynthetic yield due to the inherent limit of solid-state synthesis. Herein we report, for the first time, a new synthetic strategy that can generate new COFs via multicomponent one-pot in situ reactions. In total, 12 α-aminonitrileand quinoline-linked COFs with high crystallinity and permanent porosity are successfully achieved by three-component one-pot in situ Strecker and Povarov reactions under solvothermal conditions in high yields. The obtained COFs feature the same structures as those obtained from the stepwise PSM approach on an established imine-linked COF. This in situ multicomponent assembly strategy, as a synthetic methodology parallel to PSM, might open a new route for constructing COFs that is not possible under PSM conditions.

In this review, a comprehensive summary of the potential photocatalytic applications realized to date in the fast-growing field of COFs is provided with the aim to present a full blueprint of COFs for photochemical energy conversion and reactions.

HIGHLIGHTS Covalent organic frameworks (COFs) are first used in tumor photodynamic therapy BODIPY-decorated COFs are synthesized via bonding defects functionalization BODIPY-decorated COFs have excellent anti-tumor efficacy in vitro and in vivo COFs show great promise as nanoplatforms for biomedical applications

A porous Cu(I)-MOF was constructed from CuI and 1-benzimidazolyl-3,5-bis(4-pyridyl)benzene. This Cu(I)-MOF can be a highly sensitive naked-eye colorimetric sensor to successively detect water and formaldehyde species in a single-crystal-to-single-crystal fashion. Solid-state guest-responsive luminescence is also used to monitor the sensing process.

Herein, we report an allyl-imidazolium ionic liquid decorated COF and its covalent composite COF@chitosan aerogel, which were shown to be excellent selective CO2 adsorbents and chemical conversion catalysts.

Homochiral metal-organic frameworks with fine-tuned pore sizes/walls and large surface areas are promising porous materials for enantioseparation considering the traditional zeolite molecular sieves have no chirality. Using enantiopure pyridyl-functionalized salen [(N-(4-Pyridylmethyl)-L-leucine·HBr)] as a starting material, we have prepared a noninterpenetrated three-dimensional homochiral metal organic framework {[ZnLBr]·H2O}n, which was further used as a chiral stationary phase for high-performance liquid chromatography to enantioseparate racemic drugs, showing excellent performances in enantioseparation of drugs. The metal-organic framework can be regarded as a novel molecular sieve-like material with a chiral separation function based on the relative sizes of the chiral channels and the resolved molecules.

Two new one-dimensional organic/inorganic composite polymers were synthesized by the reaction of Cd(NO3)2·4H2O with 1,2-bis(4-pyridyl)ethyne or trans-1,2-bis(4-pyridyl)ethene in several solvent systems. [Cd(NO3)2(1,2-bis(4-pyridyl)ethyne)1.5] n (1), which has an infinite one-dimensional structure with interpenetrating molecular ladders, was obtained by reacting Cd(NO3)2·4H2O with 1,2-bis(4-pyridyl)ethyne in a methylene chloride/methanol solvent system. It crystallized in the monoclinic space group C2/c (No. 15), with a = 20.713(3) Å, b = 17.450(2) Å, c = 14.451(3) Å, β = 129.203(8)°, Z = 8. [Cd(NO3)2(1,2-bis(4-pyridyl)ethene)1.5] n (2) was generated from the reaction of Cd(NO3)2·4H2O with the trans-1,2-bis(4-pyridyl)ethene ligand in an ethanol/water system. It has a novel infinite non-interpenetrating zigzag chain structure which is made up of trans-1,2-bis(4-pyridyl)ethene−Cd−trans-1,2-bis(4-pyridyl)ethene−Cd−trans-1,2-bis(4-pyridyl)ethene building units. Compound 2 crystallized in the triclinic space group P1̄ (No. 2), with a = 10.725(2) Å, b = 10.814(2) Å, c = 9.517(2) Å, α = 104.21(2)°, β = 94.60(1)°, γ = 106.62(1)°, Z = 2. In compound 1, the Cd(II) centers lie in a heptacoordinate environment, while in compound 2, the Cd(II) atoms adopt an octahedral geometry. The two kinds of polymer structures are based on a T-shape and a linear building block, respectively. [Cd(NO3)2(1,2-bis(4-pyridyl)ethane)1.5] n (3) was also synthesized by the reaction of Cd(NO3)2·4H2O with the 1,2-bis(4-pyridyl)ethane ligand in a methylene chloride/methanol system. Polymer 3 forms square units, which are linked through the two Cd(II) centers to give infinite linear chains. The synthesis of compound 3 was reported by Fujita (Fujita, M. J. Chem. Soc., Chem. Commun. 1994, 1977) using a different solvent system.