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Photochemical CO2 reduction using ubiquitous sunlight akin to natural photosynthesis is an effective approach for conversion of renewable energy into useful chemical feedstock. Driven by the need for earth‐abundant, inexpensive, and sustainable photocatalysts with practical applicability, covalent organic frameworks (COFs) have emerged as a new generation of molecularly defined semiconductors with tunable optoelectronic properties. These reticular frameworks with highly ordered, porous and crystalline structures can be tailor‐made by covalently combining organic building blocks to target specific functions. To date, numerous COFs have been reported, which show promising activity for photocatalytic CO2 reduction allowing to derive structure–property–function relationships. In this review, the different reported strategies are comprehensively analyzed and categorized for active site engineering in COF photocatalysts and the synthetic rationale and resulting catalytic activity for each approach are discussed. The recent advancements in terms of tailored photocatalyst design are then critically assessed, aspects of advanced materials characterization are analyzed, and future perspectives and challenges for the field are highlighted. [ABSTRACT FROM AUTHOR]

Around 10–15 % of the world's energy consumption is accounted for by the separation and purification of chemicals. Among them is the enrichment and separation of isotopologues which are an essential aspect of modern chemistry. In their recent work, Su et al. demonstrate the separation of water isotopologues by responsive dynamic pore windows in a microporous coordination polymer with unprecedented selectivity based on an elegant mechanism. [ABSTRACT FROM AUTHOR]

Herein we demonstrate mesoporous frameworks interacting with carbon dioxide leading to stimulated structural contractions and massive out‐of‐equilibrium pressure amplification well beyond ambient pressure. Carbon dioxide, a non‐toxic and non‐flammable working medium, is promising for the development of pressure‐amplifying frameworks for pneumatic technologies and safety systems. The strong interaction of the fluid with the framework even contracts DUT‐46, a framework hitherto considered as non‐flexible. Synchrotron‐based in situ PXRD/adsorption experiments reveal the characteristic contraction pressure for DUT‐49 pressure amplification in the range of 350–680 kPa. The stimulated framework contraction expels 1.1 to 2.4 mmol g−1 CO2 leading to autonomous pressure amplification in a pneumatic demonstrator system up to 428 kPa. According to system level estimations even higher theoretical pressure amplification may be achieved between 535 and 1011 kPa. [ABSTRACT FROM AUTHOR]

In this Minireview, we discuss the fundamental chemistry of soft porous crystals (SPCs) by characterizing their common structural features and the resulting structural softness and transitions. In particular, we focus on the recently emerging properties based on metastable transitions and those arising from local dynamics. By comparing the resulting adsorption properties to those of commonly applied rigid adsorbents, we highlight the potential of SPCs to revolutionize adsorption‐based technologies, considering our current understanding of the thermodynamic and kinetic aspects. We provide brief outlines for the experimental and computational characterization of such phenomena and offer an outlook toward next‐generation SPCs likely to be discovered in the next decade. [ABSTRACT FROM AUTHOR]

In diesem Kurzaufsatz wird die Chemie von verformbaren porösen Kristallen (SPCs) anhand von Struktureigenschaften und deren Auswirkungen auf die Verformbarkeit und den daraus resultierenden Strukturübergang diskutiert. Besonders Eigenschaften, die auf metastabilen Übergangszuständen basieren oder durch lokale dynamische Funktionalität hervorgerufen werden, sind hierbei von Interesse. Unterschiede in den Adsorptionseigenschaften rigider poröser Materialien und denen von SPCs auf Grundlage etablierter thermodynamischer und kinetischer Aspekte zeigen das Anwendungspotenzial dieser Materialien für Adsorptionstechniken auf. Die Charakterisierung dieser Eigenschaften und die daraus resultierenden Phänomene werden dabei in den Mittelpunkt gerückt, und abschließend wird ein Ausblick auf die nächste Generation verformbarer poröser Kristalle gegeben. [ABSTRACT FROM AUTHOR]

A flexible, yet very stable metal-organic framework (DUT-98, Zr6O4(OH)4(CPCDC)4(H2O)4, CPCDC=9-(4-carboxyphenyl)-9 H-carbazole-3,6-dicarboxylate) was synthesized using a rational supermolecular building block approach based on molecular modelling of metal-organic chains and subsequent virtual interlinking into a 3D MOF. Structural characterization via synchrotron single-crystal X-ray diffraction (SCXRD) revealed the one-dimensional pore architecture of DUT-98, envisioned in silico. After supercritical solvent extraction, distinctive responses towards various gases stimulated reversible structural transformations, as detected using coupled synchrotron diffraction and physisorption techniques. DUT-98 shows a surprisingly low water uptake but a high selectivity for pore opening towards specific gases and vapors (N2, CO2, n-butane, alcohols) at characteristic pressure resulting in multiple steps in the adsorption isotherm and hysteretic behavior upon desorption. [ABSTRACT FROM AUTHOR]