Qing-Yuan Yang

Assembly of CdI2-type coordination networks from triangular ligand and octahedral metal center: topological analysis and potential framework porosity

Reaction of a rigid triangular ligand 2,4,6-tris[4-(1H-imidazole-1-yl)phenyl]-1,3,5-triazine (TIPT) with Cd2+ ions affordedrare non-interpenetrating CdI2-type networks which display high thermostability and potential porosity; the topological character of the CdI2-type networks have been analyzed in comparison with three common uniform (4,4), (6,3) and (3,6) plane nets.

An unusual 3D coordination polymer assembled through parallel interpenetrating and polycatenating of (6,3) nets

Reaction of AgClO4 with a bulky semi-flexible tripodal ligand 2,4,6-tris(4-((pyridin-4-ylthio)methyl)phenyl)-1,3,5-triazine (tppt) affords highly undulating (6,3) honeycomb networks [Ag3(tppt)2](ClO4)3·8DMSO which display unusual net entanglement. Three (6,3) nets interweave in parallel to give rise to a 3-fold interpenetrating basic layer (2D → 2D parallel). In addition, every such layer interlocks four other layers, two above and two below (2D → 3D parallel). Therefore, totally fifteen (6,3) nets are involved in entanglement with respect to each basic layer, in which each single (6,3) net shows 11-fold interpenetration and 5-fold catenation, thus resulting in a novel 3D coordination polymer containing both interpenetration and polycatenation.

Tuning Pore Size in Square‐Lattice Coordination Networks for Size‐Selective Sieving of CO2

Porous materials capable of selectively capturing CO2 from flue-gases or natural gas are of interest in terms of rising atmospheric CO2 levels and methane purification. Size-exclusive sieving of CO2 over CH4 and N2 has rarely been achieved. Herein we show that a crystal engineering approach to tuning of pore-size in a coordination network, [Cu(quinoline-5-carboxyate)2 ]n (Qc-5-Cu) ena+bles ultra-high selectivity for CO2 over N2 (SCN ≈40 000) and CH4 (SCM ≈3300). Qc-5-Cu-sql-β, a narrow pore polymorph of the square lattice (sql) coordination network Qc-5-Cu-sql-α, adsorbs CO2 while excluding both CH4 and N2 . Experimental measurements and molecular modeling validate and explain the performance. Qc-5-Cu-sql-β is stable to moisture and its separation performance is unaffected by humidity.

Photoluminescent 3D lanthanide MOFs with a rare (10,3)-d net based on a new tripodal organic linker

A new semi-rigid tripodal ligand, namely 1,1′,1′′-((2,4,6-triethylbenzene-1,3,5 triyl)tris(methylene))tris(pyridin-4(1H)-one) (L1), has been prepared by direct alkylation of 4-hydroxypyridine at the nitrogen site with 1,3,5-tris(bromomethyl)-2,4,6-triethylbenzene. The tripodal ligand has been used for the assembly of a series of isomorphous lanthanide metal–organic frameworks (Ln-MOFs) [Ln(L1)·(NO3)3]·nH2O (Ln = Eu (1), Tb (2), Sm (3), Ce (4), Gd (5); n = 3 or 4) which exhibit an unusual non-interpenetrated (10,3)-d (or utp net) topology. The photophysical properties of these lanthanide MOFs have been assessed, in which the Tb3+ complex 2 displays bright green luminescence with quite high efficiency (Φoverall = 50%) and a long excited state lifetime (τobs = 1.1 ms).

Formation of two (6,3) networks showing structural diversity, Borromean topology and conformational chirality in the same crystal

Reaction of two tripodal ligands, 2,4,6-tris(4-((2-methyl-benzimidazol-1-yl)methyl)phenyl)-1,3,5-triazine (L1) and 1,3,5-tris(4-((2-methyl-benzimidazol-1-yl)methyl)phenyl)benzene (L2), with AgSbF6 led to formation of two types (6,3) networks in one single crystal, of which one is three-fold Borromean topologically entangled while the other is independent, showing the same chirality and sandwiched Borromean stacking.

Reversible Switching between Highly Porous and Nonporous Phases of an Interpenetrated Diamondoid Coordination Network that Exhibits Gate‐Opening at Methane Storage Pressures

Herein, we report that a new flexible coordination network, NiL2 (L=4-(4-pyridyl)-biphenyl-4-carboxylic acid), with diamondoid topology switches between non-porous (closed) and several porous (open) phases at specific CO2 and CH4 pressures. These phases are manifested by multi-step low-pressure isotherms for CO2 or a single-step high-pressure isotherm for CH4 . The potential methane working capacity of NiL2 approaches that of compressed natural gas but at much lower pressures. The guest-induced phase transitions of NiL2 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 NiL2 . Specifically, the extended linker ligand, L, undergoes ligand contortion and interactions between interpenetrated networks or sorbate-sorbent interactions enable the observed switching.

Readily accessible shape-memory effect in a porous interpenetrated coordination network

An interpenetrated flexible metal-organic material exhibits only the second example of a shape-memory effect in a porous material. Shape-memory effects are quite well-studied in general, but there is only one reported example in the context of porous materials. We report the second example of a porous coordination network that exhibits a sorbate-induced shape-memory effect and the first in which multiple sorbates, N2, CO2 and CO promote this effect. The material, a new threefold interpenetrated pcu network, [Zn2(4,4′-biphenyldicarboxylate)2(1,4-bis(4-pyridyl)benzene)]n (X-pcu-3-Zn-3i), exhibits three distinct phases: the as-synthesized α phase; a denser-activated β phase; and a shape-memory γ phase, which is intermediate in density between the α and β phases. The γ phase is kinetically stable over multiple adsorption/desorption cycles and only reverts to the β phase when heated at >400 K under vacuum. The α phase can be regenerated by soaking the γ phase in N,N′-dimethylformamide. Single-crystal x-ray crystallography studies of all three phases provide insight into the shape-memory phenomenon by revealing the nature of interactions between interpenetrated networks. The β and γ phases were further investigated by in situ coincidence powder x-ray diffraction, and their sorption isotherms were replicated by density functional theory calculations. Analysis of the structural information concerning the three phases of X-pcu-3-Zn-3i enabled us to understand structure-function relationships and propose crystal engineering principles for the design of more examples of shape-memory porous materials.

Impact of partial interpenetration in a hybrid ultramicroporous material on C2H2/C2H4 separation performance

Phases of a 2-fold pcu hybrid ultramicroporous material (HUM), SIFSIX-14-Cu-i, exhibiting 99%, 93%, 89%, and 70% partial interpenetration have been obtained. 1 : 99 C2H2/C2H4 gas separation studies reveal that as the proportion of interpenetrated component decreases, so does the separation performance.

Efficient CO2 Removal for Ultra-Pure CO Production by Two Hybrid Ultramicroporous Materials

Removal of CO2 from CO gas mixtures is a necessary but challenging step during production of ultra-pure CO as processed from either steam reforming of hydrocarbons or CO2 reduction. Herein, two hybrid ultramicroporous materials (HUMs), SIFSIX-3-Ni and TIFSIX-2-Cu-i, which are known to exhibit strong affinity for CO2 , were examined with respect to their performance for this separation. The single-gas CO sorption isotherms of these HUMs were measured for the first time and are indicative of weak affinity for CO and benchmark CO2 /CO selectivity (>4000 for SIFSIX-3-Ni). This prompted us to conduct dynamic breakthrough experiments and compare performance with other porous materials. Ultra-pure CO (99.99 %) was thereby obtained from CO gas mixtures containing both trace (1 %) and bulk (50 %) levels of CO2 in a one-step physisorption-based separation process.

Supramolecular structural transformation of N,N′-bis(4-pyridylmethyl)-naphthalene diimide and fluorescence water sensing

A supramolecular structure based on N,N′-bis(4-pyridylmethyl)-naphthalene diimide exhibits reversible phase transitions in a single-crystal-to-single-crystal process. Such temperature induced SC–SC transformations are driven by intermolecular π–π interactions and hydrogen bond interaction. Interestingly, the dynamic supramolecular structure shows selective adsorption and fluorescence water sensing.