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Over the past two decades, metal–organic frameworks (MOFs) with special and designable structures, adjustable cavity size, and high surface area have attracted special attention for their applications as adsorbents, catalysts and photocatalysts, among other uses. However, due to production costs and performance, large scale and industrial usage of such materials is still limited. Particularly for the use of MOFs as adsorbents, it is essential to examine appropriate regeneration methods in order to be reusable. In other applications, particularly in catalysis, reconstruction of MOFs is necessary in order to regain the initial activity of fresh materials and facilitate their application at industrial scale. The goal of this review is to provide a comprehensive assessment of the regeneration procedures and reconstruction techniques for MOF adsorbents based on the existing data. This discussion is further extended to describe the impact of temperature, pressure, and moisture on the interaction between adsorbent/adsorbate molecules, and the stability and capacity of sorbents after regeneration. This review will help readers to gain insights into the desorption process in MOF as adsorbents under different regeneration conditions.

A review of the synthesis, structure and specifically the effect of counter-ions on the properties of ionic metal organic frameworks (ionic-MOFs) is presented, highlighting the important advances in this regard over the past decade. Most focus is on ionic porous metal–organic frameworks (MOFs) materials consisting of porous anionic or cationic frameworks and cationic or anionic guests. The structure and performance of cationic and anionic MOFs are influenced by several factors, such as organic ligands, metal ions and charge-balancing anions. These types of anionic and cationic materials have distinct advantages in comparison with neutral MOFs in the design of functional materials and their synthesis affords several distinct advantages over that for routine neutral frameworks by virtue of the isolated charged species in confined nano-spaces. The nanosized and charged pores in these ionic structures generate a strong interaction between the host and guest molecules, including enhanced adsorption towards small gases and solvent molecules. Ionic-MOFs can be easily modified via ion exchange and accommodate other charged guest molecules, making them an ideal platform for different applications, such as functional materials. The development of synthesis methods by ion exchange and the potential applications of such cationic or anionic structures have been discussed thoroughly in this review.

New 2D lead(II) coordination polymers, Pb(4-bpdh)(CH3COO)(NO3)]n (1) and [Pb(4-bpdh)(ClO4)(NO3)]n (2), 4-bpdh ​= ​2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene, were prepared and characterized by single-crystal X-ray diffraction. Compound 3 with formula [Pb(4-bpdh)(NO3)2(H2O)]n (3) was obtained by solid state mechanochemical reaction of the compounds 1 and 2 via anion-exchange process. These conversions are reversible and the grinding of compound 3 with CH3COO¯ and ClO4¯ ions led to the formation of the compounds 1 and 2, respectively. Thermal decomposition of the compounds 1–3 results in the formation of different metallic composites. The composites were characterized by X-ray powder diffraction (XRD) and size and morphology of them were investigated by scanning electron microscopy (SEM).

Four new Zn(II) and Cd(II) coordination polymers, [Zn(2-AMP)2(N3)2]n (1), [Zn(2-AMP)2(SCN)2]n (2), [Cd(2-AMP)(N3)2]n (3) and [Cd(2-AMP)2(SCN)2]n (4) {2-AMP: 2-Aminomethylpyridine}, have been synthesized and characterized by single crystal X-ray diffraction, IR spectroscopy and elemental analyses. The Zinc(II) oxide and Cadmium(II) oxide nano-particles have been synthesized from thermolysis of 1–4 at 600 °C under air atmosphere for 4 h. The ZnO and CdO nanoparticles were characterized by X-ray diffraction and scanning electron microscopy (SEM). SEM images show the average size of produced ZnO and CdO nanoparticles are 60–70 nm in all compounds.

Two Zinc(II) coordination polymers [Zn(NO2)2(3-bapp)]n·nH2O (1) and [Zn(NO2)2(4-bapp)]n·nH2O (2) have been synthesized by using zinc acetate, sodium nitrite, {3-bapp: 2,6-bis (3-amidopyridyl) pyridine} and {4-bapp: 2,6-bis (4-amidopyridyl) pyridine} as precursor. Pure phase ZnO nano-rods were obtained by thermolyses of compound 1 and 2 in 600 °C for 3 h under air atmosphere. The ZnO nano-rods were characterized by X-ray diffraction and scanning electron microscopy. The average crystallite size of ZnO nano-rods (1), (2) were determined 30 and 40 nm respectively. The particle size of hexagonal nano-rods of (1) and (2) are in the range of 20–70 and 30–80 nm respectively. The photo-catalytic performance of degradation of Congo red solution was increased when the particles size were decreased.

Supported palladium nanoparticles on Mn-carboxylate coordination polymer (Pd/MnBDC) were prepared using solution impregnation method. This new catalyst was characterized by XRD, SEM, TEM, EDX, XPS, FTIR and TGA analysis. The Pd/MnBDC exhibits efficient catalytic activity for the Mizoroki–Heck coupling reaction between iodobenzene and either aromatic or aliphatic terminal alkenes and reuses up to four runs without significant loss of activities.

Two mercury(II) complexes [Hg(4-mtrt)Cl2] (1) and [Hg(4-mtrt)Br2] (2), have been synthesized from reaction of ligand 4-methyl-4H-1,2,4-triazole-3-thiol (4-mtrt) with HgCl2 and HgBr2. Structures of compound 1–2 have been characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. The nanoparticles of compound 1–2 have been prepared by sonochemical method. The new nano-structures were characterized by scanning electron microscopy, elemental analysis, IR spectroscopy and X-ray diffraction (XRD). The size of the samples prepared by sonochemical method are about 50 and 60 nm in compounds 1 and 2 respectively.

Two zinc(II) complexes [Zn(6,6′-dimethyl-2,2′-bipy)Cl2]n (1) and [Zn(6,6′-dimethyl-2,2′-bipy)I2]n (2) are synthesized from the reaction of the 6,6′-dimethyl-2,2′-bipy ligand with ZnCl2 and ZnI2. Zinc(II) oxide nanoparticles are synthesized by the thermolysis of [Zn(6,6′-dimethyl-2,2′-bipy)Cl2]n (1) and [Zn(6,6′-dimethyl-2,2′-bipy)I2]n (2) at two different temperatures. The ZnO nanoparticles are characterized by X-ray diffraction and scanning electron microscopy (SEM). SEM images show the average size of the ZnO nanoparticles produced of 50 nm and 60 nm in compounds 1 and 2 respectively.

Nano-particles of two new Cd(II) supramolecular complexes, [Cd(4,4-di-tert-bubipy)Cl2(DMSO)] (1) and [CdI2(4,4′-dmbpy)(DMSO)] (2) have been synthesized by sonochemical process and characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and elemental analyses. The structure of compound 1 has been characterized by single crystal X-ray diffraction. The prepared nano-structure was characterized by scanning electron microscopy and X-ray powder diffraction. The nano-structures of supramolecular complexes have been synthesized with calcination of complexes at oleic acid as a surfactant at 190 oC too. The size of the samples prepared by sonochemical method and calcination are about 30–40 and 40–50 nm respectively.

Two new nano-structured Hg(II) supramo- lecular complexes, (Hg(5,5 0 -di-t-but-bpy)(l-Br)Br)2(Hg(5, 5 0 -di-t-but-bpy)Br2)(1) and (Hg(5,5 0 -di-t-but-bpy)I2 )( 2) were synthesized by the sonochemical method. The struc- tures of 1 and 2 were characterized by elemental analysis, IR, 1 H-NMR, and 13 C-NMR spectroscopy and single crystal X-ray diffraction. Their thermal stabilities were studied by thermogravimetric and differential thermal analyses. Solid-state luminescent spectra of 1 and 2 indi- cate a fluorescent broad emission band between 304 and 404 nm with excitation at 284 nm. These nanostruc- tured coordination polymers were characterized by scan- ning electron microscopy, elemental analysis, and IR spectroscopy.

A new coordination polymer of lead(II) nitrate complexes with bridging trans-1,2-bis(4-pyridyl)ethene (bpe) ligand, [Pb(µ-NO3)2(bpe)(MeOH)]n (1), has been synthesized and characterized by elemental analysis, FT-IR, 1H, 13C-NMR, thermal analysis and single crystal X-ray diffraction. In compound 1, lead(II) ions are bridged by nitrate ligands forming linear chains, which are also further coordinated by neutral bpe and methanol ligands into a two-dimensional polymeric chain. This polymeric precursor has been used to prepare PbO nano-particles using two different method. The prepared lead(II) oxide nano-structure was characterized by scanning electron microscopy and X-ray powder diffraction.

Nano-structures of Pb(II) 2-D coordination polymers, [Pb2(µ-2-bpdbe)2(NO3)4] n (1) {2-bpdbe = 1,6-bis(2-pyridyl)-2,5-diaza-1,5-hexadiene}, were synthesized by the sonochemical method. The structure of 1 may be considered a coordination polymer of lead(II) formed by bridging 2-bpdbe ligands, making a 2-D array of Pb(NO3)2 and 2-bpdbe. The thermal stability of the material was studied by thermal gravimetric and differential thermal analyses. The new nano-structure coordination polymer was characterized by scanning electron microscopy, elemental analysis, and IR spectroscopy. The sizes of the nano-structures were approximately 50 nm. Nano-particles were obtained by thermolysis of 1 in oleic acid as a surfactant at 180°C and 200°C under air atmosphere and the size of the PbO particles were about 60 nm.

A new nano-coordination polymer of lead(II) nitrate with the ethylenediamine (en) ligand, [Pb(en)(NO3)2] n (1), has been synthesized by a sonochemical process and characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and elemental analyses. The structure of 1 has been characterized by single crystal X-ray diffraction. In 1, Pb(II) ions are bridged by nitrate ligands forming linear chains, which are also further coordinated by neutral en ligands. This polymeric precursor has been used to prepare Pb(II)O nano-particles using two different methods. The prepared Pb(II)O nano-structure was characterized by scanning electron microscopy and X-ray powder diffraction.

A new nano-sized Zn(II) complex, [Zn(5,5′-dtbu-2,2′-bipy)Cl2] n (1) was synthesized and its structure determined by X-ray crystallography. The new nano-sized complex was prepared at oleic acid as a surfactant at 280 °C and characterized by scanning electron microscopy, elemental analyses and IR spectroscopy. The ZnO nano-particles were synthesized from thermolysis of nano-compound 1 at 600 °C and similar compound, [Zn(5,5′-dimethyl-2,2′-bipy)Cl2] n (2), at two different methods. SEM images show the average size of ZnO nano-particles are 78 and 50 nm for the compounds 1 and 2, respectively.

Two new lead(II) nitrate coordination polymers from ligand 1,2-di-(4-pyridyl)-ethylene (bpe), [Pb2(μ-bpe)3(μ-NO3)2(NO3)2]n (1) and {[Pb(μ-bpe)(μ-NO3)2(NO3)(H2O)]·(Hbpe)·0.5(bpe)}n (2), were synthesized. The compounds 1 and 2 were characterized by IR spectroscopy, elemental analyses and X-ray crystallography. The structures of 1 and 2 may be considered coordination polymers of lead(II) consisting of metallocyclic chains formed by bridging bpe ligands, making two- and one-dimensional array of Pb(NO3)2 and bpe, respectively. Pure phase PbO nano-particles were obtained by thermolyses of compounds 1–2 in oleic acid as surfactant at 180 and 200 °C under air atmosphere. The PbO nanoparticles were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM).

A new nano-sized lead(II) coordination polymer, {[Pb2(μ-3-bpdh)(μ-NO3)3(NO3)]n (1); (3-bpdh = 2,5-bis(3-pyridyl)-3,4-diaza-2,4-hexadiene)}, was synthesized by a sonochemical method. The structure of 1, which may be considered coordination polymer of lead(II), consists of metallocyclic chains formed by bridging NO3 − and 3-bpdh ligands, thereby making a 2D array of Pb(NO3)2 and 3-bpdh. The thermal stability of compound was studied by thermogravimetric and differential thermal analyses. The new nano-structure coordination polymer was characterized by powder X-ray diffraction, elemental analysis and IR spectroscopy. The scanning electron microscopy shows the particle size of the 1 prepared by the sonochemical method is about 95 nm. The PbO nanoparticles were obtained by thermolysis of 1 at 180 °C with oleic acid as a surfactant. The scanning electron microscopy shows that the size of the PbO particles are ~60 nm.

A reversible crystal-to-crystal transformation of a 1D lead(II) coordination polymer to a 2D lead(II) coordination polymer with the ligand 1,2-di-(4-pyridyl)-ethylene (bpe), [Pb2(μ-bpe)3(μ-NO3)2(NO3)2(H2O)2]n (1) to [Pb2(μ-bpe)3(μ-NO3)2(NO3)2]n (2), by de- and rehydration has been observed and the structures of 1 and 2 were determined by single crystal X-ray diffraction. The thermal stabilities of compounds 1 and 2 were studied by thermal gravimetric and differential thermal analyses. Powder X-ray diffraction experiments showed that the phase transitions observed for the single crystals also occur in the batch powder samples and lead to monophasic products. Nano-particles of compound 1 were synthesized by a sonochemical process and characterized by scanning electron microscopy (SEM), powder X-ray diffraction, IR spectroscopy and elemental analyses. The SEM images showed that no change in the morphology occurs during this dynamic crystal-to-crystal conversion.