This review presents comprehensively recent progress in metal-metalloporphyrin frameworks (MMPFs) with an emphasis on versatile functionalities. Following a brief introduction of basic concepts and the potential virtues of MMPFs, we give a snapshot of the historical perspective of MMPFs since 1991. We then summarize four effective strategies implemented frequently to construct prototypal MMPFs. MMPFs represent a resurging class of promising functional materials, highlighted with diverse applications including guest-molecule adsorption and separation, catalysis, nano-thin films and light-harvesting.

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Crystal engineering of the nbo metal-organic framework (MOF) platform MOF-505 with a custom-designed azamacrocycle ligand (1,4,7,10-tetrazazcyclododecane-N,N',N'',N'''-tetra-p-methylbenzoic acid) leads to a high density of well-oriented Lewis active sites within the cuboctahedral cage in MMCF-2, [Cu2(Cu-tactmb)(H2O)3(NO3)2]. This MOF demonstrates high catalytic activity for the chemical fixation of CO2 into cyclic carbonates at room temperature under 1 atm pressure.

Herein, we report that a new flexible coordination network, NiL (L=4-(4-pyridyl)-biphenyl-4-carboxylic acid), with diamondoid topology switches between non-porous (closed) and several porous (open) phases at specific CO and CH pressures. These phases are manifested by multi-step low-pressure isotherms for CO or a single-step high-pressure isotherm for CH . The potential methane working capacity of NiL approaches that of compressed natural gas but at much lower pressures. The guest-induced phase transitions of NiL were studied by single-crystal XRD, in situ variable pressure powder XRD, synchrotron powder XRD, pressure-gradient differential scanning calorimetry (P-DSC), and molecular modeling. The detailed structural information provides insight into the extreme flexibility of NiL . Specifically, the extended linker ligand, L, undergoes ligand contortion and interactions between interpenetrated networks or sorbate-sorbent interactions enable the observed switching.

A majority of metal-organic frameworks (MOFs) fail to preserve their physical and chemical properties after exposure to acidic, neutral, or alkaline aqueous solutions, therefore limiting their practical applications in many areas. The strategy demonstrated herein is the design and synthesis of an organic ligand that behaves as a buffer to drastically boost the aqueous stability of a porous MOF (JUC-1000), which maintains its structural integrity at low and high pH values. The local buffer environment resulting from the weak acid-base pairs of the custom-designed organic ligand also greatly facilitates the performance of JUC-1000 in the chemical fixation of carbon dioxide under ambient conditions, outperforming a series of benchmark catalysts.

The tunability of the band gaps in Zn-based metal-organic frameworks (MOFs) has been experimentally demonstrated via two different approaches: changing the cluster size of the secondary building unit (SBU) or alternating the conjugation of the organic linker.

Self-assembly of the custom-designed octatopic porphyrin ligand of tetrakis(3,5-dicarboxybiphenyl)porphine with the in situ generated Cu2(CO2)4 paddlewheel moieties afforded a porous metal-metalloporphyrin framework, MMPF-9, which features a high density of Cu(II) sites confined within nanoscopic channels and demonstrates excellent performances as a heterogeneous Lewis-acid catalyst for chemical fixation of CO2 to form carbonates at room temperature under 1 atm pressure.

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