Advances in flexible and functional metal–organic frameworks (MOFs), also called soft porous crystals, are reviewed by covering the literature of the five years period 2009–2013 with reference to the early pertinent work since the late 1990s. Flexible MOFs combine the crystalline order of the underlying coordination network with cooperative structural transformability. These materials can respond to physical and chemical stimuli of various kinds in a tunable fashion by molecular design, which does not exist for other known solid-state materials. Among the fascinating properties are so-called breathing and swelling phenomena as a function of host–guest interactions. Phase transitions are triggered by guest adsorption/desorption, photochemical, thermal, and mechanical stimuli. Other important flexible properties of MOFs, such as linker rotation and sub-net sliding, which are not necessarily accompanied by crystallographic phase transitions, are briefly mentioned as well. Emphasis is given on reviewing the recent progress in application of in situ characterization techniques and the results of theoretical approaches to characterize and understand the breathing mechanisms and phase transitions. The flexible MOF systems, which are discussed, are categorized by the type of metal-nodes involved and how their coordination chemistry with the linker molecules controls the framework dynamics. Aspects of tailoring the flexible and responsive properties by the mixed component solid-solution concept are included, and as well examples of possible applications of flexible metal–organic frameworks for separation, catalysis, sensing, and biomedicine.

Direct electrochemical reduction of CO₂ to fuels and chemicals using renewable electricity has attracted significant attention partly due to the fundamental challenges related to reactivity and selectivity, and partly due to its importance for industrial CO₂-consuming gas diffusion cathodes. Here, we present advances in the understanding of trends in the CO₂ to CO electrocatalysis of metal- and nitrogen-doped porous carbons containing catalytically active M–N _x moieties (M = Mn, Fe, Co, Ni, Cu). We investigate their intrinsic catalytic reactivity, CO turnover frequencies, CO faradaic efficiencies and demonstrate that Fe–N–C and especially Ni–N–C catalysts rival Au- and Ag-based catalysts. We model the catalytically active M–N _x moieties using density functional theory and correlate the theoretical binding energies with the experiments to give reactivity-selectivity descriptors. This gives an atomic-scale mechanistic understanding of potential-dependent CO and hydrocarbon selectivity from the M–N _x moieties and it provides predictive guidelines for the rational design of selective carbon-based CO₂ reduction catalysts.

A new mesoporous MOF, Zn₄O(bpdc)(btctb)_4/3 (DUT-32), containing linear ditopic (bpdc²⁻; 4,4′-biphenylenedicarboxylic acid) and tritopic (btctb³⁻; 4,4′,4′′-[benzene-1,3,5-triyltris(carbonylimino)]tris-benzoate) linkers, was synthesised. The highly porous solid has a total pore volume of 3.16 cm³ g⁻¹ and a specific BET surface area of 6411 m² g⁻¹, adding this compound to the top ten porous materials with the highest BET surface area.