Is there no way to bypass greenhouse gasses by converting excess heat to longerwave radiation?

One thing to keep in mind is that such conversion is itself a thermodynamic process, which necessarily has finite efficientcy. Thus, there will be heating effect due to the conversion itself.

When discussing global warming it is important to keep in mind the basic thermodynamics. The warming as a consequence of the efficiency of any human devices being elss than 1, as required by the second law of thermodynamics. The rejected heat is in essence the warming, and the realistic ways of reducing it is either reducing the energy consumption, or using more efficient technologies (which may produce some paradoxal results when comparing the "green energy" with the fossil or the nuclear).

The effective irradiation of the heat by earth is only a part of the picture, and unlikely the key to the permanent solution of the problem (since we may eventually run into other problems, if Earth is continuously to lose more and more heat).

If we however accept this as a solution, then the answer to the question depends on the balance between the efficientcy of (i.e., the warming due to) the frequency conversion vs. the improving the irradiation of energy by Earth.