Robust ultra-microporous metal-organic frameworks for highly efficient natural gas purification

The development of highly efficient separation technology for the purification of natural gas by removing ethane(C_(2)H_(6))and propane(C_(3)H_(8))is a crucial but challenging task to their efficient utilization in the chemical industry and social life.Here,we report three isomorphic ultra-microporous metal-organic frameworks(MOFs),M-pyz(M=Fe,Co,and Ni,and pyz=pyrazine)referred to as Fe-pyz,Co-pyz,and Ni-pyz,respectively,which possess high density of open metal sites and suitable pore structure.Compared with the benchmark materials reported,M-pyz not only has high adsorption capacities of C_(2)H_(6)and C_(3)H_(8)at low pressure(up to 51.6 and 63.7 cm^(3)·cm^(−3)),but also exhibits excellent C_(3)H_(8)/CH_(4)and C_(2)H_(6)/CH_(4)ideal adsorption solution theory(IAST)selectivities,111 and 25,respectively.Theoretical calculations demonstrated that the materials’separation performance was driven by multiple intermolecular interactions(hydrogen bonding interactions and van der Waals effect)between gas molecules(C_(2)H_(6)and C_(3)H_(8))and the M-pyz binding sites.And,dynamic breakthrough experiments verified the superior reusability and practical separation feasibility for the ternary CH_(4)/C_(2)H_(6)/C_(3)H_(8)mixtures.Furthermore,M-pyz can be synthesized rapidly and on a large scale at room temperature.This work presents a series of promising MOFs adsorbents to efficiently purify natural gas and promotes the industrial development process of MOFs materials.

Crystal engineering of porous coordination networks for C3 hydrocarbon separation

C3 hydrocarbons(HCs),especially propylene and propane,are high‐volume products of the chemical industry as they are utilized for the production of fuels,polymers,and chemical commodities.Demand for C3 HCs as chemical building blocks is increasing but obtaining them in sufficient purity(>99.95%)for polymer and chemical processes requires economically and energetically costly methods such as cryogenic distillation.Adsorptive separations using porous coordination networks(PCNs)could offer an energy‐efficient alternative to current technolo-gies for C3 HC purification because of the lower energy footprint of sorbent separations for recycling versus alternatives such as distillation,solvent extraction,and chemical transformation.In this review,we address how the structural modularity of porous PCNs makes them amenable to crystal engineering that in turn enables control over pore size,shape,and chemistry.We detail how control over pore structure has enabled PCN sorbents to offer benchmark performance for C3 separations thanks to several distinct mechanisms,each of which is highlighted.We also discuss the major challenges and opportunities that remain to be addressed before the commercial development of PCNs as advanced sorbents for C3 separation becomes viable.

A square lattice topology coordination network that exhibits highly selectiveC_(2)H_(2)/CO_(2)separation performance

C_(2)H_(2)/CO_(2)separation is an industrially important process that remains challenging because of the similar physicochemical properties of C_(2)H_(2)and CO_(2).We herein report that the new square lattice(sql)coordination network[Cu(bipy‐xylene)2(NO3)2]n,sql‐16‐Cu‐NO3,16=bipy‐xylene=4,4′‐(2,5‐dimethyl‐1,4‐phenylene)dipyridine,exists in at least three forms,as‐synthesised(α),activated(α′)and hydrated(β).The activated phase,sql‐16‐Cu‐NO3‐α′,is an ultramicroporous material that exhibits high selectivity towards C_(2)H_(2)over CO_(2)as revealed by dynamic gas breakthrough experiments(1:1,C_(2)H_(2)/CO_(2))that afforded 99.87%pure CO_(2)in the effluent stream.The separation selectivity at 298 K and 1 bar,78,is the third best value yet reported for C_(2)H_(2)selective physisorbents whereas the mid‐loading performance sets a new benchmark.The performance of sql‐16‐Cu‐NO3‐α′is attributed to a new type of C_(2)H_(2)binding site in which CH···ONO2 interactions enable moderately strong sorbent‐sorbate binding(Qst(C_(2)H_(2))=38.6 kJ/mol)at low loading.Conversely,weak CO_(2)binding(Qst(CO_(2))=25.6 kJ/mol)at low loading means that(ΔQst)AC[Qst(C_(2)H_(2))–Qst(CO_(2))]is 13 kJ/mol at low coverage and 11.4 kJ/mol at mid‐loading.Analysis of in situ powder X‐ray diffraction and modelling experiments provide insight into the sorption properties and high C_(2)H_(2)/CO_(2)separation performance of sql‐16‐Cu‐NO3‐α′.