Graphitic carbon
nitride materials have attracted significant interest
in recent years and found applications in diverse light-to-energy
conversions such as artificial photosynthesis, CO2 reduction,
or degradation of organic pollutants. However, their utilization in
synthetic photocatalysis, especially in the direct functionalization
of C(sp3)–H bonds, remains underexplored. Herein,
we report mesoporous graphitic carbon nitride (mpg-CN) as a heterogeneous
organic semiconductor photocatalyst for direct arylation of C(sp3)–H bonds in combination with nickel catalysis. Our
protocol has a broad synthetic scope (>70 examples including late-stage
functionalization of drugs and agrochemicals), is operationally simple,
and shows high chemo- and regioselectivities. Facile separation and
recycling of the mpg-CN catalyst in combination with its low preparation
cost, innate photochemical stability, and low toxicity are beneficial
features overcoming typical shortcomings of homogeneous photocatalysis.
Detailed mechanistic investigations and kinetic studies indicate that
an unprecedented energy-transfer process (EnT) from the organic semiconductor
to the nickel complex is operating.
In recent years, the porous sorbent-assisted atmospheric water harvesting (AWH) method has emerged as an effective approach for solving water crises without geographical restrictions. However, there is a limited array of porous adsorbent materials that can be used for AWH, which are inadequate to meet the needs under different climatic conditions. In light of this, herein, we synthesize a new crystalline porous organic salt (CPOS; denoted as CPOS-6) possessing a dual hydrogen bond system and verify its applicability toward AWH for the first time. Unlike other reported CPOSs, CPOS-6 displays an S-shaped water sorption isotherm owing to the presence of the dual hydrogen bond system. Under simulated drought conditions in Xinjiang Uygur Autonomous Region, CPOS-6 exhibits long-term water adsorption-desorption cycling stability, low water desorption temperature, and ultrarapid adsorption-desorption kinetics. The results confirm that CPOS-6 is an effective sorbent material for AWH.
In the wake of sustainable development, materials research is going through a green revolution that is putting energy-efficient and environmentally friendly materials and methods in the limelight. In this quest for greener alternatives, covalent organic frameworks (COFs) have emerged as a new generation of designable crystalline porous polymers for a wide array of clean-energy and environmental applications. In this contribution, we categorically review the merits and shortcomings of COF bulk powders, nanosheets, freestanding thin films/membranes, and membranes on porous supports in various separation processes, including separation of gases, pervaporation, organic solvent nanofiltration, water purification, radionuclide sequestration, and chiral separations, with particular reference to COF material pore size, host–guest interactions, stability, selectivity, and permeability. This review covers the fabrication strategies of nanosheets, films, and membranes, as well as performance parameters, and provides an overview of the separation landscape with COFs in relation to other porous polymers, while seeking to interpret the future research opportunities in this field.
The unique structural characteristics of threedimensional (3D) covalent organic frameworks (COFs) like high surface areas, interconnected pore system and readily accessible active sites render them promising platforms for a wide set of functional applications. Albeit promising, the reticular construction of 3D COFs with large pores is a very demanding task owing to the formation of interpenetrated frameworks. Herein we report the designed synthesis of a 3D non-interpenetrated stp net COF, namely TUS-64, with the largest pore size of all 3D COFs (47 Å) and record-low density (0.106 g cm À 3 ) by reticulating a 6-connected triptycenebased linker with a 4-connected porphyrin-based linker. Characterized with a highly interconnected mesoporous scaffold and good stability, TUS-64 shows efficient drug loading and controlled release for five different drugs in simulated body fluid environment, demonstrating the competency of TUS-64 as drug nanocarriers.
Three-dimensional (3D) covalent organic frameworks (COFs)
exemplify
a new generation of crystalline extended solids with intriguing structures
and unprecedented porosity. Notwithstanding substantial scope, the
reticular synthesis of 3D COFs from pre-designed building units leading
to new network topologies yet remains a demanding task owing to the
shortage of 3D building units and inadequate reversibility of the
linkages between the building units. In this work, by linking a tetragonal
prism (8-connected) node with a square planar (4-connected) node,
we report the first 3D COF with scu-c topology. The new
COF, namely, TUS-84, features a two-fold interpenetrated structure
with well-defined porosity and a Brunauer–Emmett–Teller
surface area of 679 m2 g–1. In drug delivery
applications, TUS-84 shows efficient drug loading and sustained release
profile.
Self‐assembled crystalline porous organic salts (CPOSs) formed by an acid–base combination and with one‐dimensional polar channels containing water molecules have been synthesized. The water content in the channels of the porous salts plays an important role in the proton conduction performance of the materials. The porous salts described in this study feature high proton conductivity at ambient conditions and can reach as high as 2.2×10−2 S cm−1 at 333 K and under high humid conditions. This is among the best conductivity values reported to date for porous materials, for example, metal–organic frameworks and hydrogen‐bonded organic frameworks. These materials exhibiting permanent porosity represent a group of porous materials and may find interesting applications in proton‐exchange membrane fuel cells.
Endowed with chiral channels and pores,c hiral metal-organic frameworks (MOFs) are highly useful;h owever,their synthesis remains achallenge given that most chiral building blocks are expensive.A lthough MOFs with induced chirality have been reported to avoid this shortcoming,n o study providing evidence for the ee value of such MOFs has yet been reported. We herein describe the first study on the efficiency of chiral induction in MOFs using inexpensive achiral building blocks and fully recoverable chiral dopants to control the handedness of racemic MOFs.This method yielded chirality-enriched MOFs with accessible pores.T he ability of the materials to form host-guest complexes was probed with enantiomers of varying size and coordination and in solvents with varying polarity.F urthermore,m ixed-matrix membranes (MMMs) composed of chirality-enriched MOF particles dispersed in apolymer matrix demonstrated anew route for chiral separation.
We report the synthesis of 1,4-dicarbonyl compounds and substituted alkenes (Mizoroki–Heck type coupling) starting from secondary and tertiary alkyl halides and vinyl acetate or styrene derivatives using visible-light photocatalysis.
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