This Research Front, dedicated to Coordination Polymers (materials also known as metal-organic frameworks), comprises a selection of papers representing the current look of this rapidly growing field. These materials have crystalline porous structures with potential applications in areas such as gas storage, separations, catalysis, biomedicine, and sensing.

A series of discrete and polymeric copper coordination complexes featuring the 4,4'-methylenebis(1-(2-pyridyl)-3,5-dimethylpyrazole) ligand are reported, along with discussion of the structural diversity and some unexpected solvothermal reactivity.

The synthesis of the triazolium ligand 1,4-bis(4-benzoic acid)-1-methyl-1H-1,2,3-triazolium chloride, H₂L1^Me, was used to explore the potential of metal–organic frameworks as catalyst supports. Under controlled conditions, H₂L1^Me reacts with copper(ii) nitrate to generate both potentially porous and close-packed 2D structures.

A series of six silver(i) trifluoroacetate complexes containing new ligands each composed of a quinolinyl or pyridyl nucleus bearing one or two terminal ethynyl substituent(s) has been synthesised and characterised by X-ray crystallography. The coordination preferences of the ethynide substituent(s) at variable positions with respect to the nitrogen donor atom serve as dominant factors in directing the construction of multi-dimensional organosilver(i) networks.

The thermal expansion, optical, and redox properties of a series of squarate-based frameworks, [M^II(C₄O₄)(H₂O)₂] (M^II = Mn^II, Fe^II, Co^II, Ni^II, Zn^II, and Cd^II), have been investigated.

A new flexible tritopic ligand, 1,3,5-tri(4-cyanophenoxy)benzene, was shown to form three-dimensional coordination polymers that include benzene or toluene and dichloromethane as guest molecules. The luminescent properties of crystalline solid 1 were found to change significantly on complexation with Ag^I.

The interaction of flexible two- and three-armed ligands with silver salts is shown to be a useful method for the self-assembly of coordination polymers. The substitution pattern of two- and three-armed ligands produces a range of complexes characterised by crystallography.

The three-connecting ligands 2,4,6-tris(4′-pyridyl)-1,3,5-triazine (4-tpt) and 2,4,6-tris(3′-pyridyl)-1,3,5-triazine (3-tpt) have been utilised to prepare five 3D framework materials. It is shown that a range of different framework phases form depending on subtle variation in reaction conditions.

Zn²⁺, 1,2-di(4-pyridyl)ethane, and several isophthalates provide a series of 2D layer porous coordination polymers which show distinct adsorption isotherms for CO₂, CH₄, C₂H₄, and C₂H₆ at 195 K and 273 K.

Carrying out organic reactions in aqueous or aqueous-organic systems has ecological and economical advantages. In aqueous microemulsions, micelle structures are formed where organic transformations take place. This review discusses recent developments and challenges in the application of the microemulsion approach towards transition metal catalyzed organic reactions.

Solvent-induced reversible crystal-to-amorphous transformation properties with chromotropism in the supramolecular network of [Co(Hampy)₂(H₂O)₄](SO₄)₂(H₂O)₃ (1) is demonstrated. Although there is a lack of a coordination bridge to maintain the skeleton of the framework structure, the original crystalline form is recovered from collapsed amorphous structures by the restoration of water and methanol molecules.

This paper proposes a sensing strategy which employs aptamer, unmodified gold nanoparticles (AuNP), and hexadecyltrimethylamonium bromide to detect tetracycline in raw milk. The method is based on the colourimetric assays via aggregating AuNP, and the detection limit is 122 Nm.

2-{2-[4-(4-[¹⁸F]-Fluorobenzyl)piperazin-1-yl]-2-oxoethyl}isoindolin-1-one ([¹⁸F]MEL054), a new potent indolinone-based melanin binder designed to target melanotic tumours, was prepared by an automated, two-step radiosynthesis, comprising of the preparation of 4-[¹⁸F]fluorobenzaldehyde from 4-formyl-N,N,N-trimethylanilinium triflate, followed by reductive alkylation with 2-(2-oxo-2-piperazin-1-ylethyl)isoindolin-1-one. HPLC purification produced [¹⁸F]MEL054 in 34 ± 9 %, >99 % radiochemical purity.

Polyguanidine is used as a novel and highly efficient catalyst in the Knoevenagel reaction of aldehydes with active methylene compounds in water to afford substituted electrophilic alkenes. The polyguanidine catalyst can be recovered by simple filtration and reused many times for the aqueous Knoevenagel reaction without loss of activity.