Electrostatic charges patterning along crystalline channels recognize CO2 with high selectivity and promote its fast screwing dynamics through the crystal at one million steps per second, strongly reminiscent of trans-membrane transport in biological channels.

In the organic matter dynamic and fluid phases cannot survive down to temperatures of a few kelvins, temperature at which only low-inertial-mass groups, such as methyls, may exhibit fast rotation. Here we fabricate 3D-architectures of spontaneous molecular rotors by engineering in metal organic frameworks full-fledged barrierless rotors with exceptionally-low activation energy of 6.2 small cal mol-1. The trigonal bipyramidal symmetry of the rotator in the struts was frustrated by its arrangement in the cubic crystal cell, generating high multiplicity of 12 shallow minima per turn, with a benchmark 10 10 Hertz frequency persistent even below 2K. The nearly degenerated energy landscape allows for continuous unidirectional hyper-fast rotation, which lasts for hundreds of turns, by 'overflying' several minima. Such an impressive dynamic performance in solid organic matter is only comparable to that of methyl rotation, opening new fields of application whenever hyper-fast dynamics at extremely-low temperatures and minimization of thermal-noise are needed.

Despite use of blended cements containing significant amounts of aluminum for over 30 years, the structural nature of aluminum in the main hydration product, calcium aluminate silicate hydrate (C-A-S-H), remains elusive. Using first-principles calculations, we predict that aluminum is incorporated into the bridging sites of the linear silicate chains and that at high Ca:Si and H2O ratios, the stable coordination number of aluminum is six. Specifically, we predict that silicate-bridging [AlO2(OH)4]5– complexes are favored, stabilized by hydroxyl ligands and charge balancing calcium ions in the interlayer space. This structure is then confirmed experimentally by one- and two-dimensional dynamic nuclear polarization enhanced 27Al and 29Si solid-state NMR experiments. We notably assign a narrow 27Al NMR signal at 5 ppm to the silicate-bridging [AlO2(OH)4]5– sites and show that this signal correlates to 29Si NMR signals from silicates in C-A-S-H, conflicting with its conventional assignment to a “third aluminate hydrate” (TAH) phase. We therefore conclude that TAH does not exist. This resolves a long-standing dilemma about the location and nature of the six-fold-coordinated aluminum observed by 27Al NMR in C-A-S-H samples.

Channel expansion of flexible molecular architectures endowed with porosity has been proved to be responsive to gas stimuli, such as pressurized CO2, CH4, Xe and hydrocarbons.