Ordered nanoporosity in covalent organic framework (COF) offers excellent opportunity for property development. Loading nanoparticles (nPs) onto them is one approach to introducing tailor-made properties into a COF. Here, a COF-Co/Co(OH) composite containing about 16 wt% of <6 nm sized Co/Co(OH) nPs is prepared on a N-rich COF support that catalyzes the release of theoretical equivalence of H from readily available, safe, and cheap NaBH . Furthermore, the released H is utilized for the hydrogenation of nitrile and nitro compounds to amines under ambient conditions in a facile one-pot reaction. The COF "by choice" is built from "methoxy" functionalized dialdehydes which is crucial in enabling the complete retention of the COF structure under the conditions of the catalysis, where the regular Schiff bonds would have hydrolyzed. The N-rich binding pockets in the COF ensure strong nP-COF interactions, which provides stability and enables catalyst recycling. Modeling studies reveal the crucial role played by the COF in exposing the active facets and thereby in controlling the activation of the reducing agent. Additionally, via density functional theory, we provide a rational explanation for how these COFs can stabilize nanoparticles which grow beyond the limiting pore size of the COF and yet result in a truly stable heterogeneous catalyst - a ubiquitous observation. The study underscores the versatility of COF as a heterogeneous support for developing cheap and highly active nonnoble metal catalysts.

Owing to long spin-relaxation time and chemically customizable physical properties, molecule-based semiconductor materials like metal-phthalocyanines offer promising alternatives to conventional dilute magnetic semiconductors/oxides (DMSs/DMOs) to achieve room-temperature (RT) ferromagnetism. However, air-stable molecule-based materials exhibiting both semiconductivity and magnetic-order at RT have so far remained elusive. We present here the concept of supramolecular arrangement to accomplish possibly RT ferromagnetism. Specifically, we observe a clear hysteresis-loop (H ≈ 120 Oe) at 300 K in the magnetization versus field (M-H) plot of the self-assembled ensembles of diamagnetic Zn-phthalocyanine having peripheral F atoms (ZnFPc; S = 0) and paramagnetic Fe-phthalocyanine having peripehral H atoms (FePc; S = 1). Tauc plot of the self-assembled FePc···ZnFPc ensembles showed an optical band gap of ∼1.05 eV and temperature-dependent current-voltage (I-V) studies suggest semiconducting characteristics in the material. Using DFT+U quantum-chemical calculations, we reveal the origin of such unusual ferromagnetic exchange-interaction in the supramolecular FePc···ZnFPc system.

An oxyborate Co2AlBO5 belonging to the ludwigite family is investigated using structural, thermodynamic, dielectric and magnetic measurements. Magnetic measurements indicate that this system is seen to exhibit long range magnetic ordering at T N = 42 K, signatures of which are also seen in the specific heat, dielectric susceptibility, and the lattice parameters. The absence of a structural phase transition down to the lowest measured temperatures, distinguishes it from the more extensively investigated Fe-based ludwigites. At low temperatures, the system is seen to stabilize in a reentrant superspin glass phase at T G = 10.6 K from within the magnetically ordered state. This ground state is also characterized by magnetic field induced metamagnetic transitions, which at the lowest measured temperatures exhibit a number of sharp magnetization steps, reminiscent of that observed in the mixed valent manganites.

We report on the magnetic, thermodynamic, dielectric, and pyroelectric measurements on the hitherto unreported Fe4Ta2O9. This system is seen to exhibit a series of magnetic transitions, many of which are coupled to the emergence of ferroelectric order, making Fe4Ta2O9 the only genuine multiferroic in its material class. We suggest that the observed properties arise as a consequence of an effective reduction in the dimensionality of the magnetic lattice, with the magnetically active Fe 2+ ions preferentially occupying a quasi 2D buckled honeycomb structure. The low temperature H-T phase diagram of Fe4Ta2O9 reveals a rich variety of coupled magnetic and ferroelectric phases, in similarity with that observed in the distorted Kagome systems.

We report the observation of a Griffiths Phase in the geometrically frustrated antiferromagnet DyBaCo4O 7+δ . Its onset is determined using measurements of the thermoremanent magnetization, which is shown to be superior to conventional in-field measurement protocols for the identification of the Griffiths Phase. Within this phase, the temporal relaxation of magnetization exhibits a functional form which is expected for Heisenberg systems, reflecting the nature of spin interactions in this class of materials. Interestingly, the effective Co 2+ /Co 3+ ratio tailored by varying the oxygen non-stoichiometry δ is only seen to influence the antiferromagnetic ordering temperature (T N ), leaving the Griffiths Temperature (T G) invariant.Keywords: Keywords A Griffiths Phase (GP) pertains to the formation of arbitrarily large magnetically ordered regions within the global paramagnetic phase, at temperatures exceeding that of long range magnetic ordering. First postulated in the context of random site dilution in Ising ferromagnets [1], this phase is characterized by the magnetization remaining non-analytical at temperatures above the ferromagnetic Curie temperature (T C ), where the system is neither a pure paramagnet, nor does it exhibit long range order. Analyticity is restored only above the Griffiths temperature T G , which refers to the Curie Temperature of the pristine (undiluted) system. This model was further generalized to account for random magnetic spin systems, where T G now refers to the highest ordering temperature allowed by the bond probability distribution [2]. The physics of this regime between T C and T G is now known to be extremely rich, and has even been extended to Quantum Phase Transitions where these effects are thought to manifest themselves in the form of power laws in thermodynamical observables [3]. This area of research saw renewed interest, when it was suggested that the phenomenon of Colossal Magnetoresistance observed in mixed valent manganites could be understood in the context of a Griffiths Singularity [4]. A variety of factors like doping, Jahn Teller distortion [5], size variance of the A site ions in the ABO 3 structure [6], finite size effects [7] and magnetic site dilution [8] were seen to stabilize a GP in these materials. This phenomena appears to be ubiquitous to a number of strongly correlated electron systems, and materials as diverse as transition metal oxides [5][6][7][8][9], chemically substituted f -electron systems [10] and magnetocaloric intermetallics [11,12] are now reported to harbor such a state.The probability of a magnetically ordered rare region existing within a global paramagnetic phase would fall exponentially as the volume of this region [13] . Thus the experimental verification of the GP primarily relies on our ability to detect the contribution which this rare region makes to measurable thermodynamic quantities. The most popular route has been to evaluate the inverse of the measured zero field cooled (ZFC) dc magnetic susceptibility χ −1 = (T −T C ) 1−λ , w...