Rational design of new in situ reduction of Ni(II)catalytic system for low-cost and large-scale preparation of porous aromatic frameworks

Porous aromatic framework 1(PAF-1)is an extremely representative nanoporous organic framework owing to its high stability and exceptionally high surface area.Currently,the synthesis of PAF-1 is catalyzed by the Ni(COD)2/COD/bpy system,suffering from great instability and high cost.Herein,we developed an in situ reduction of the Ni(II)catalytic system to synthesize PAF-1 in low cost and high yield.The active Ni(0)species produced from the NiCl_(2)/bpy/NaI/Mg catalyst system can effectively catalyze homocoupling of tetrakis(4-bromophenyl)methane at the room temperature to form PAF-1 with high Brunauer-Emmett-Teller(BET)-specific surface area up to 4948 m^(2) g^(−1)(Langmuir surface area,6785 m2 g−1).The possible halogen exchange and dehalogenation coupling mechanisms for this new catalytic process in PAF's synthesis are discussed in detail.The efficiency and universality of this innovative catalyst system have also been demonstrated in other PAFs'synthesis.This work provides a cheap,facile,and efficient method for scalable synthesis of PAFs and explores their application for high-pressure storage of Xe and Kr.

A step‐growth strategy to grow vertical porous aromatic framework nanosheets on graphene oxide:Hybrid material‐confined Co for ammonia borane methanolysis

The rational synthesis of a two-dimensional(2D)porous aromatic framework(PAF)with a controllable growth direction remains a challenge to overcome the limitation of traditional stacked 2D materials.Herein,a step-growth strategy is developed to fabricate a vertically oriented nitrogen-rich porous aromatic framework on graphene oxide(V-PAF-GO)using monolayer benzidine-functionalized GO(BZ-GO)as a molecular pillar.Then,the confined Co nanoparticle(NP)catalysts are synthesized by encapsulating ultra-small Co into the slit pores of V-PAF-GO.Due to the high nitrogen content,large specific surface area,and adequate slit pores,the optimized vertical nanocomposites V-PAF-GO provide abundant anchoring sites for metal NPs,leading to ultrafine Co NPs(1.4 nm).The resultant Co/V-PAF-GO catalyst shows an extraordinary catalytic activity for ammonia borane(AB)methanolysis,yielding a turnover frequency value of 47.6 min−1 at 25°C,comparable to the most effective non-noble-metal catalysts ever reported for AB methanolysis.Experimental and density functional theory studies demonstrate that the electron-donating effect of N species of PAF positively corresponds to the low barrier in methanol molecule activation,and the cleavage of the O–H bond in CH3OH has been proven to be the rate-determining step for AB methanolysis.This work presents a versatile step-growth strategy to prepare a vertically oriented PAF on GO to solve the stacking problem of 2D materials,which will be used to fabricate other novel 2D or 2D–2D materials with controllable orientation for various applications.

Silver-anchored porous aromatic framework for efficient conversion of propargylic alcohols with CO_(2) at ambient pressure

The conversion of propargylic alcohols and carbon dioxide(CO_(2)) into fine chemicals suffers from issues of harsh reaction conditions and difficult catalyst recovery. To achieve efficient CO_(2)activation at low energy consumption, a silver-anchored porous aromatic framework catalyst Ag@PAF-DAB with high active phase density and CO_(2)adsorption capacity was proposed. Since Ag@PAF-DAB has the dual functions of CO_(2)capture and conversion, propargylic alcohols were completely converted into α-alkylidene cyclic carbonate or α–hydroxy ketone as high value-added product under atmospheric pressure(CO_(2), 0.1 MPa) and low silver equivalent(0.5 mol%). Notably, Ag@PAF-DAB exhibited broad substrate diversity, high stability,and excellent reusability. By applying FTIR and GC, the key to green synthetic route of α–hydroxy ketone was confirmed to lie in the further hydration of α-alkylidene cyclic carbonate.

Frustrated Lewis pairs in situ formation in B-based porous aromatic frameworks for efficient o-phenylenediamine cyclization

Benzimidazoles are very important chemical materials in the pharmaceutical industry,and the most common synthetic route is cyclization of o-phenylenediamine with carbon sources,in which utilization of inexpensive and abundant CO_(2)as C1 source is very impressive.Porous aromatic frameworks(PAFs)with highly desired skeletons have attracted great attentions in gas capture and catalysis.Herein,B-based PAF-165 and PAF-166 are designed and synthesized via Friedel-Crafts alkylation reaction,which present high surface areas as well as high stability.Benefiting from the abundant electron-deficient B centers,both PAFs exhibit excellent selective CO_(2)adsorption abilities.The presence of sterically hindered B units in PAFs can act as Lewis acid active sites for the frustrated Lewis pairs(FLPs)in situ formation with ophenylenediamine,thus promoting the synthesis of benzimidazole.The optimal reaction conditions for o-phenylenediamine cyclization with PAF catalysts are explored,and the reaction mechanism is also proposed.This work provides feasible ideas for incorporating FLPs within porous materials as reusable heterogeneous catalysts for CO_(2)capture and conversion.

Synthetic subnanochannels in porous aromatic frameworks accelerate selective water permeation in membrane desalination

Creation of freeways in a membrane accelerates water transport for efficient desalination;however,the synthesis of target membrane materials is very challenging.In the present study,the molecular-design strategy is developed for the synthesis of porous aromatic framework(PAF)membranes with rigid and open networks to regulate water transport.Nitrile-based monomers in triangle shape are designed for the construction of PAF-98 and its sister frameworks,and these PAF membranes are formed through trifluoromethanesulfonic acid catalysis.The rigidity and geometry of the monomers endow PAFs with unique structures of connected pores with edging size(4.5–6.7Å)between water(2.8Å)and hydrated sodium molecules(7.2Å),enabling effective differentiation of water and salt.The fabricated membranes with high flexibility and continuity are ideal for water desalination,and reverse osmosis experiments demonstrate that the three PAF membranes are selective for permeation of water molecules over hydrated sodium cations.Unprecedented water flux of 547.1 L m^(-2) h^(-1) and high rejection degree of 90%are obtained on a representative membrane of PAF-98-E;and the desalination performance is superior to currently available membrane materials.Furthermore,PAF-98-E membrane is capable of rejecting various cations with high efficiency in real seawater,holding great promise in practical water desalination application.

High energy and insensitive explosives based on energetic porous aromatic frameworks

The design and synthesis of energetic materials with a compatibility of high energy and insensitivity have always been the research fronts in military and civilian fields.Considering excellent performances of porous organic frameworks and the lack of research in the field of energetic materials,in this study,a new concept named energetic porous aromatic frameworks(EPAFs)is proposed.The strategy of coating high energy explosives such as 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane(CL-20)and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX)in the EPAFs by wet-infiltration method has successfully realized the assembly of target energetic composite materials.The results show that the 75 wt.%CL-20@EPAF-1 possesses the safer impact sensitivity of 31.4 J than that of CL-20(4.0 J).Notably,for 75 wt.%CL-20@EPAF-1,in addition to the superior detonation performances of the detonation velocity(8,761 m·s^(-1))and detonation pressure(31.27 GPa),the synergistic effect of the nitrogen-rich EPAFs and the nitramines high energy explosives results in a higher heat of detonation that surpasses the most of pristine high explosives and reported novel energetic materials.In prospect,energetic porous aromatic frameworks could be a promising and inspiring strategy to build high energy insensitive energetic materials.

Novel Porous Aromatic Framework with Excellent Separation Capability of CO2 in N2 or CH4

A novel porous aromatic framework, PAF-52, was obtained via the polymerization of tetrahedral mono- mer tetrakis（4-cyanodiphenyl） methane（TCDPM） with the aid of a facile ionothermal method. PAF-52 has a surface area of 1159 m2/g（BET）, and shows a considerable high separation ability of CO2 in N2 or CH4 respectively at room temperature, using gas-chromatography experiments as evidence,

Targeted synthesis of novel porous aromatic frameworks with selective separation of CO_2/CH_4and CO_2/N_2

Novel porous aromatic frameworks（PAF-53 and PAF-54） have been obtained by the polymerization of amino compound（p-phenylenediamine and melamine） and cyanuric chloride. They display a certain amount of CO2 adsorption capacity and highly selective separation of CO2/CH4 and CO2/N2 as 18.1 and83 by Henry Law respectively. They may be applied as ideal adsorbents to separate and capture CO2.

Synthesis of porous aromatic framework with Friedel–Crafts alkylation reaction for CO_2 separation

A novel porous aromatic framework, PAF-8, derived from tetraphenylsilane as basic building unit, was successfully synthesized via Friedel-Crafts alkylation reaction. This PAF material had high thermal stability as well as high surface area （785 m^2 g^-1） calculated from the Brunauer-Emmett-Teller （BET） model. Meanwhile, PAF-8 possessed high performances in gas sorption and especially for CO2 separation.

Porous aromatic framework(PAF-1) as hyperstable platform for enantioselective organocatalysis

High density of phenyl rings makes PAF-1 have robust structure and highly lipophilic pore, which make it very suitable for organocatalysis. However, there is no report about using PAF-1 as platform for enantioselective organocatalysis.In this paper, using PAF-1 as the platform, a chiral prolinamide catalytic site was introduced onto the framework of PAF-1 via a series of stepwise post-synthetic modifications,obtaining a novel PAF-supported chiral catalyst named PAF-1-NHPro. Then its enantioselective catalytic performance was studied by subjecting it to catalyze the model Aldol reaction between p-nitrobenzaldehyde and cyclohexanone.PAF-1-NHPro showed good diastereoselectivity and enantioselectivity with excellent and easy recyclability.