Developing highly efficient photocatalyts for water splitting is one of the grand challenges in solar energy conversion. Here, we report the rational design and synthesis of porous conjugated polymer (PCP) that photocatalytically generates hydrogen from water splitting. The design mimics natural photosynthetics systems with conjugated polymer component to harvest photons and the transition metal part to facilitate catalytic activities. A series of PCPs have been synthesized with different light harvesting chromophores and transition metal binding bipyridyl (bpy) sites. The photocatalytic activity of these bpy-containing PCPs can be greatly enhanced due to the improved light absorption, better wettability, local ordering structure, and the improved charge separation process. The PCP made of strong and fully conjugated donor chromophore DBD (M4) shows the highest hydrogen production rate at ∼33 μmol/h. The results indicate that copolymerization between a strong electron donor and weak electron acceptor into the same polymer chain is a useful strategy for developing efficient photocatalysts. This study also reveals that the residual palladium in the PCP networks plays a key role for the catalytic performance. The hydrogen generation activity of PCP photocatalyst can be further enhanced to 164 μmol/h with an apparent quantum yield of 1.8% at 350 nm by loading 2 wt % of extra platinum cocatalyst.

Using a facile approach, we successfully made large “defect-free” hyperbranched polystyrene (PSt) chains with uniform subchains between two branching points from the interchain “clicking” of a seesaw-type linear macromonomer [azide∼∼∼alkyne∼∼∼azide] prepared by ATRP with a following conversion of two bromine-ends into two azide-ends, where ∼∼∼ denotes a PSt chain (1.65–31.0 kg/mol). The “click” reaction kinetics monitored by a combination of size exclusion chromatography (SEC) and laser light scattering (LLS) reveals that the degree of self-polycondensation (DP) is related to the reaction time (t) as ln(DP+ 1)/2 = ([A]0 k AB,0)/β arctan(βt), where [A]0 and k AB,0 are the initial alkyne concentration and the initial reaction rate between the azide and alkyne groups, respectively; β is a constant and its reciprocal (1/β) represents the time at which k AB = k AB,0/2. The results reveal that 1/β is scaled to the macromonomer’s molar concentration ([C]) and molar mass (M) as 1/β ∼ [C]−0.35 M 0.55, indicating that 1/β is governed by the interchain distance and diffusion, respectively. Each hyperbranched sample can be further fractionated into a set of narrowly distributed “defect-free” hyperbranched chains with different molar masses by precipitation. The LLS results show, for the first time, that the root-mean-square radius of gyration (⟨R g⟩) and hydrodynamic radius (⟨R h⟩) of “defect-free” hyperbranched polystyrenes in toluene at 25 °C are scaled to the weight-average molar mass (M w) as ⟨R g⟩ = 5.53 × 10–2 M w 0.464 and ⟨R h⟩ = 2.95 × 10–2 M w 0.489, respectively, where the exponents are smaller than the predicted 1/2.

The 3C-like protease of SARS coronavirus (SARS-CoV 3CL(pro)) is vital for SARS-CoV replication and is a promising drug target. It has been extensively proved that only the dimeric enzyme is active. Here we discovered that two adjacent mutations (Ser139_Ala and Phe140_Ala) on the dimer interface resulted in completely different crystal structures of the enzyme, demonstrating the distinct roles of these two residues in maintaining the active conformation of SARS-CoV 3CL(pro). S139A is a monomer that is structurally similar to the two reported monomers G11A and R298A. However, this mutant still retains a small fraction of dimer in solution, which might account for its remaining activity. F140A is a dimer with the most collapsed active pocket discovered so far, well-reflecting the stabilizing role of this residue. Moreover, a plausible dimerization mechanism was also deduced from structural analysis. Our work is expected to provide insight on the dimerization-function relationship of SARS-CoV 3CL(pro).