The development of catalysts based on earth abundant metals in place of noble metals is becoming a central topic of catalysis. We herein report a cobalt/tetraphosphine complex-catalyzed homogeneous hydrogenation of polar unsaturated compounds using an air-and moisture-stable and scalable precatalyst. By activation with potassium hydroxide, this cobalt system shows both high efficiency (up to 24 000 TON and 12 000 h −1 TOF) and excellent chemoselectivities with various aldehydes, ketones, imines, and even N-heteroarenes. The preference for 1,2reduction over 1,4-reduction makes this method an efficient way to prepare allylic alcohols and amines. Meanwhile, efficient hydrogenation of the challenging N-heteroarenes is also furnished with excellent functional group tolerance. Mechanistic studies and control experiments demonstrated that a Co I H complex functions as a strong hydride donor in the catalytic cycle. Each cobalt intermediate on the catalytic cycle was characterized, and a plausible outer-sphere mechanism was proposed. Noteworthy, external inorganic base plays multiple roles in this reaction and functions in almost every step of the catalytic cycle.

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The supply of domestic hot water (DHW) on college and university campuses is indispensable and is also one of the main components of campus energy consumption. The density of residential patterns and similar occupancy behavior of college students make it economical to use centralized systems to cover the DHW demand, and utilization of solar energy can make the systems more economical. Seasonal thermal energy storage (STES) is a promising key technology that can minimize the imbalance between the availability of solar energy and thermal energy demand. In this paper, a solar-assisted ground-coupled heat pump (SAGCHP) system that meets the DHW demand of 960 students was investigated by means of dynamic simulation and energy-economic analysis. The simulation results in terms of the underground heat balance are compared with a standalone GCHP system and a SAGCHP system without STES. Results show that heat recharging operations during university summer and winter breaks (when there are minimal students on campus) lead to improved underground heat balance and energy performance. Finally, a sensitivity analysis on system performance was carried out by varying solar collector arrays. It was found that there exists an optimal value of solar collector area to achieve the lowest system lifecycle cost (LCC).

The chemoselective hydrogenation of unsaturated compounds has been a powerful tool for both synthetic chemistry and chemical industry. The achievement of chemoselectivity among different functionalities with a single catalyst has been a challenge for transition metal-catalyzed hydrogenation. In this paper, iron tetraphosphine complexes show high catalytic efficiency for a variety of polar unsaturated substrates such as aldehydes, ketones, enones, nitroarenes and N-heteroaromatics. Without an N-H group on the catalyst, the chemoselectivity was controlled precisely by the reaction temperature. The catalytic efficiency, chemoselectivity and robustness of this Fe/P4N2 catalyst found its merit in the preparation of several important drug intermediates. A diamagnetic trans-iron dihydride complex, formed under the reaction conditions, was supposed to be an on-cycle catalytically active species.<br>

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